Sea Doo Jet Boat – High Performance Mods

Updates – This document covers aftermarket components available at the time of authoring. As addition components become available, we will be updating this document to reflect the performance of those parts. Edit Date 9/22/99.

The Models – This document is specific to the single engine Bombardier 14.5 foot jet-boats manufactured and sold from 1996 through 1999. While there are a number of subtle feature changes among all these models, there are two basic design platforms. They are as follows:

718cc Model – This version uses the 82mm bore x 68mm stroke two cylinder Rotax rotary valve marine engine. With the exception of some electrical components, this is exactly the same 720cc Rotax engine used in numerous pwc models. While this engine is known to have reliable operation and good fuel range in recreational applications, it is lacking in low rpm range horsepower…even in the lightweight two-seat pwc hulls.

782cc Models – While this engine is only 64cc larger, it is a whole different engine design with much better overall power and potential. The two biggest design features of this 82mm bore x 74mm stroke engine are the variable exhaust valves (aka RAVE valves), and the built in harmonic balancer. Along with these features, the 782cc engine has slightly larger 40mm carbs (38’s on the 718), and a much more “heavy duty” construction about all the lower end components.

About The Dual Motor Boats – While this document is specific to issues of the single engine/single pump Sea Doo boats, the modification information herein also applies to the dual motor machines. We are in the process of testing with the twin engine models to establish ideal impeller pitches, etc. When we have that data, we will be posting a separate document for them on our website.

Jet-Boat Use Applications – Folks purchase the 14.5 single motor jet-boats for many different uses. By far the most common thread to all these uses is the need to occasionally traverse through shallow waters that might damage a conventional propeller boat drive. The 14.5 boats are nearly unmatched in their ability to navigate safely through waters as shallow as 2 feet.

This document will sometimes specify some modifications that are ideally suited for one particular use application. So keeping your primary use application in mind is important. The uses are as follows:

Towing Sports – The “stock” 14.5’s do an acceptable job of towing wake boarders and inflatable’s. Group K offers a number of modifications that dramatically improve this ability, and make these boats the ideal tube/board tow-boat. However as good as we can make the single motor 14.5’s, towing heavy and/or single ski water skiers is an application these boats are “not” well suited for…you can do it…but it’s not easy.

Destination – The 14.5 boats are ideally suited for transporting two or three people (and their stuff) over a large distance of reasonably smooth water. Whether the activity is fishing or touring, these boats have great potential for increased speed (to cover distance), and increased fuel efficiency (to improve fuel range). Transporting 4 people should only be attempted on “smooth or glass” water conditions (the front seat is a punishing ride in the rough).

Sport – We use this term to describe aggressive operation in any water conditions. Usually this involves one or two passengers in rough water conditions at median to high speeds. Despite their short length, these 14.5’s can cover very rough lake chop (at high speed) with excellent handling and control. The bulk of our testing was done in this kind of use because it is the most stressful use (on the boat). While we have seen owners use these machines for recreational big surf jumping, this use can be very punishing to the boat and occupants…we tend to recommend against it.

About Porpoising – In smooth water and mild wind-chop, the 14.5’s drive straight and smooth at speed…but rolling wave water is another story. If the 14.5’s have one huge shortcoming, it is the chronic nose bouncing, known to pwc riders as “porpoising” (so called because it mimics a porpoise’s jumping movement). This porpoising takes place anytime the 14.5’s encounter sequential rolling waves (like those that come from other passing crafts). Since the 14.5’s have no trim system, the porpoising cannot be “trimmed” out (as on larger boats). There is no foreseeable mechanical “fix” for this problem (bolt-on or otherwise). However there is a steering “strategy” that can have a huge impact on reducing the problem.

The hull shape of the 14.5’s is designed in such a way that a very slight turning of the steering wheel can immediately reduce (or stop) the porpoising action. When the hull is set slightly to one side (as in a gentle turn) the side face of the hull immediately absorbs the wave action of rolling waves…and the porpoising stops. The boat can be steered very slightly from side to side (in sweeping turns) to abate porpoising in very rough water conditions. In situations that do not permit this kind of “constant turning”, merely backing off the throttle will dramatically reduce the porpoising as well.

Operational Weakness Areas – There are a few weakness areas where our modifications can help a particular problem…but some of the problems can never be “completely” eliminated. Understanding these areas can help you to better suit your 14.5 for your use application.

Take Off Thrust – On initial take-off from a dead stop, “all” single pump 14.5’s experience some level of cavitation. Cavitation takes place when the prop spins in a partially “airiated” water supply (it feels like a slipping clutch). This same cavitation (in a lesser degree) is also experienced by some pwc’s that use this same driveline. The added weight of the 14.5 hull, and the added resistance of the bigger “wetted surface” make it nearly impossible to perform a swift take off (from a dead stop) without cavitation. The added resistance of a heavy water skier makes a swift take off virtually impossible.

With pump upgrades, this cavitation can be greatly reduced to the extent that take-offs with an inflatable, or boarder, are easy. However the sheer weight of the boat and passengers assure that every swift takeoff (even with an upgraded pump) will exhibit some cavitation. Along with the correct pump upgrades, you can eliminate most of this cavitation, and “manage” the rest.

Acceleration from Turns – Because of the mechanical dynamics of the single stage pump design, turning will always have a noticeable effect on engine rpms. In high speed “left hand” turns, the water enters the pump cavity at an angle that is “unfriendly” to the rotation of the prop. The result is that engine rpms will drop significantly from this added “load”. Conversely, turning right at high speed causes the water to enter the pump at an angle that allows the prop to process water very easily. The load reduction caused by this “favorably” entering water can be so profound that the engine rpms raise significantly, and cavitation is often induced.

Both of these effects of high speed turning can be greatly reduced by switching to custom impellers of different blade designs and pitches. These impellers, and their features, are discussed below.

Weed Debris in Pump – While this doesn’t sound like a big deal…it can be. During operation, long strands of grass or seaweed can pass through the scoop grate and become caught on the leading edges of the impeller. This debris causes profound vibration, as well as cavitation that makes planeing speeds impossible. While you would think the impeller would simply cut the grass and clear it out, that doesn’t always happen. The solution to this unfortunate situation is to swim under the boat and physically remove the debris, or idle the boat back to the launch ramp to clear the debris out of the water. There are “many” situations where neither one of these options is convenient or desirable. The best solution we have found is based in the use of an impeller that “can” cut nearly any sea grasses. See the “Impellers” section below for that information.

The Pump – While the pump on the single motor 14.5’s may be a bit under built for some use applications, it has a great deal of potential and room for improvement. The following details those areas.

Pump Shoe – The pump shoe is the actual metal part (bolted to the hull) that the pump body seals up against. In the case of the 14.5’s, the shoe and the ride plate are made as one piece. It is “fundamental” that this shoe/ride plate is perfectly sealed to the hull with a high-grade silicone sealer. Herein lies a lot of the cavitation problems experienced by many 14.5 owners. Many of these shoes came from the factory with breeches in the silicone that sealed them to the hull. On these units, no kind of custom prop, etc, can eliminate the cavitation. The pump shoe/ride plate “must” be removed and resealed using “Permitex 66c Industrial Clear Silicone” (available in auto parts stores). Removal of the pump shoe is difficult (usually done with a hydraulic jack between the plate and the rear swim step). Once off, all surfaces must be completely cleaned of the old sealer. It is impossible to over emphasize the absolute importance of have this area attended to. We recommend This procedure for “every” single motor 14.5.

As added insurance to sealing between the pump shoe and pump case, we recommend a foam pump sealing-ring (available from the SD dealer). This inexpensive foam ring assures that there are no unknown gaps in the crucial sealing surface between the pump case and the pump shoe.

Wear Ring – The wear ring is a removable Teflon plastic liner that the impeller spins within. In a perfect world, this ring has no grooves or gouges on its surface, and it fits closely to the impeller’s outside diameter. However there can be considerable cavitation if the wear ring is gouged or grooved (as can happen from digestion of rocks or branches). In addition to the cavitation, a damaged wear ring reduces pump efficiency in a way that can cause the engine to run a few 100 rpm higher than normal (for any given speed). The end result is reduced pump thrust, and reduced fuel range. If your wear ring is damaged in anyway, it’s cost effective to replace it…and then stay away from rocks.

Drive Shaft Protector – The 14.5’s come from the factory with a white plastic sheath that slips over the drive shaft. This free spinning sheath is intended to make it easier to remove ropes that might get wrapped around the drive shaft. Unfortunately, the forces of debris entering the pump often causes this protector to fracture and break apart, thus contributing to cavitation. We chose to cut this protector off at the front of the drive shaft (a small part of it must remain to seal the shaft), thus increasing the pump’s water intake area. At this same time we shortened our dock-lines to a length that would bake it impossible for them the wrap the drive shaft when tied to the cleats on the top deck.

Pump Blue Printing – For most recreational applications, the stock Sea Doo pump assembly works fine. For owners that want to “fine tune” the stock pump, we recommend pump blueprinting. This blue printing consists of eliminating all the casting drafts and surface interruptions in the pump vane body. This pump blueprinting does not increase smooth water peak speeds, however it can make a noticeable improvement in rough water hook up ability.

Impellers – About Impeller Pitch: Please note that impeller pitch selection is a function of the power output of your engine setup, and relies on the presumption that you have a well sealed pump shoe and good condition wear ring. Also note that “all” impeller makers have their own means of measuring and stating pitch angles. This means that a 16/23° from one manufacturer will have completely different engine loading characteristics than a 16/23° from another manufacturer. Pitch angle comparison is “only” relevant so long as the brand is the same. At Group K we have tested all the popular impellers to find the correct pitches for our engine packages.

About Blade Design – The stock impeller can work okay, however it’s design if far from optimum. There are two aftermarket impellers that offer a significant improvement over the stocker.

The Swirl Props – These impellers, manufactured by Skat Trak in the USA, are the most versatile and effective prop for any 14.5. The swirl is so called because of it’s radially sweeping blade that tapers all the way up to the nose of the impeller. In essence, the swirl prop has the same effect on the 14.5 that wide tires would have on a race car. The swirl design gives this prop a lot more water contact surface area, and thereby a lot less cavitation. The swirl “completely” eliminates the cavitation in high-speed right hand turns (that all other props exhibit). Furthermore, it makes a “huge” reduction in the cavitation experienced during a take off from a dead stop. The only down side to the swirl prop is a slight reduction in peak water-speed. This reduction is a result of the extra drag caused by the extra surface area. However, even with that speed loss, we consider the swirl a mandatory upgrade for anyone using their 14.5 in a “towing” or “sport riding” application…the added hook up is well worth the speed loss…and then some.

An added feature of the swirl impeller is it’s ability to “cut and clear” debris…better than any other prop. The tapered blades of the swirl allow grass to easily get moved between the prop blade and the wear ring, where they are cut and blown through…blender style. We consider the swirl prop to be a mandatory upgrade for anyone operating is grassy or seaweed laden waters.

Since Skat Trak does not manufacture an impeller with the correct pitch for the 14.5 boats, all new Skat Trak impellers purchased from Group K are re-pitched by us to the correct spec for your engine arrangement.

The Solas Props – These props are a conventional style blade that is cast to a special contoured diameter hub. The contour of this hub allows the Solas to generate a lot more thrust per rpm than any other impeller. The end result is that the Solas can generate better mph-per-rpm than any other impeller (by about 2 – 3 mph). This is ideal for “destination” users who simply want to cover distance between two points with the maximum efficiency.

The only functional down sides to the Solas are the propensity to get grass debris caught on it’s blades (like the stock prop), and considerable right turn cavitation (also like the stock prop). While the Solas props do not have the full versatility of the swirl props, their sheer efficiency cannot be ignored. Like The Skat Trak props, Solas does not manufacture an impeller with the correct pitch for the 14.5 boats, all new Solas impellers purchased from Group K are re-pitched by us to the correct spec for your engine arrangement.

Engine Performance Goals – The 718cc and 782cc engines used in these 14.5s are popular platforms that have been used in pwc’s for a long time. Given that, there are many performance shops (including Group K) that already have lots of performance knowledge about these engines. However our testing has led us to see that the 14.5s have a whole different set of priorities that require a much different approach to higher performance. In short, many of the modifications available for the 718/782cc pwc’s would be a flat out “bad” choice for a 14.5 jet-boat.

Besides the very obvious priority of rock solid reliability, precise speed-control, and good fuel-range are also important to the 14.5’s. The exhaust pipes and ignition curves of the 14.5’s are tuned to deliver maximum power between 6800 – 6950 rpm. We urge 14.5 owners to avoid modifications intended to operate at higher rpms than that. Considerably higher rpms can compromise fuel range and reliability, not to mention the loss in low end power that often accompanies “high rpm” oriented parts or modifications. Many pwc owners purchase modifications that will net “quicker throttle response”. This quicker response is fundamental on a pwc for the purpose of good steering control, as well as rough water maneuvering. However those needs are not an issue for the 14.5’s, hence those types of modifications have less benefit and less effect on the 14.5. The following text explains our views on the full gambit of popular modifications.

Compression – No modification is more popular, and more effective than increasing compression. On pwc’s, compression increases are often referred to in terms of “psi” (pounds per square inch) as measured with a compression gauge. We tend to avoid using psi numbers as a standard because there are so many variables that can result in erroneous readings (see our website document “About Compression). Instead we use head volume specifications and compression ratios to accurately set up compression.

Every shop has it’s own ideas on the safe limits of compression ratio for various pwc models. However as a rule, most of those ratios are too high for safe and reliable “pump gas” use in a 14.5. Unlike pwc’s, the 14.5’s are often operated with a heavy load of passengers, gear, towable’s, etc. With these high loads (that most pwc’s won’t experience), there is an increased risk of high engine temperature (if an excessive compression ratio is used). For this reason, our Group K cylinder head modifications for the 14.5 jet-boats is a ratio slightly lower than what might conventionally be used in a pwc application. Just the same, this modification yields a good increase in overall acceleration and peak rpm, along with the ability to operate safely on 89 octane fuel (although 92 octane is better).

Flame Arrestor/Air Filter – The installation of a “freer breathing” aftermarket flame arrestor is one of the most popular performance bolt-on’s for pwc’s. These aftermarket “flame arrestors” do allow for the inlet of additional air. However they also compromise a very important feature of the stock inlet system called “signal strength”.

While the carbs on these Rotax engines may appear to somewhat crude, they actually possess a very unique “self adjusting” quality. With each opening of the inlet ports, there is a strong negative pressure wave (aka vacuum) sent up the inlet port to the fuel atomizers in the carbs. This vacuum varies as engine loads increase and decrease. The carbs “sense” this variation in vacuum, and deliver slightly greater or larger amounts of fuel as the inlet tract demands it. With the stock flame arrestor in place, this vacuum remains high for a very long time (in relationship to a cycle duration). This means that the conservative “restriction” offered by the stock arrestor actually helps to accentuate this self compensating feature. (for more detail on “signal”, see our website document, “Racing Carburetors 1999”)

When a free breathing arrestor is installed, the inlet passage vacuum is significantly reduced, and so too is some of this self-compensating fuel delivery ability. If the machine is run primarily at full throttle (like a pwc), the high-speed fuel mixture screws can be tuned to offer safe fuel delivery at full throttle. However with the reductions in inlet passage vacuum, there can random “lean spots” in many parts of the partial throttle rpm range. This is no problem for small pwc’s who remain at these partial-throttle settings for only a few moments at a time. However it can be a temperature risk for a loaded 14.5 that demands a precise amount of fuel over a wide range of different cruising rpms. The only exception to this rule might be “sport” application machines that will be operated primarily at full throttle. For these machines, we recommend the aluminum R&D plenum type flame arrestor (it has the carb brace that we consider to be mandatory).

For primarily this reason of “signal”, we recommend to retain the stock flame arrestor on all 14.5 boats. With the stock arrestors, you are assured the smoothest possible rpm control, as well as very accurate fuel metering. An added plus of the stock arrestor is that it seriously muffles the significant “inlet noise” generated by the carbs (after a couple of hours, it can drive you nuts).

Carburation – There are a wide array of high performance carburetors available for the 718cc and 782cc powered pwc’s. The main thrust of these carbs is to dramatically increase acceleration and throttle response on pwc’s. Along with those increases can come considerable increases in peak rpm ability. While these are all wonderful qualities for a pwc application, they are less attractive in a single motor 14.5 application. Since a perfectly set up 14.5 pump is already cavitating when the throttle is applied quickly, an increase in throttle response will only lead to increased cavitation…not increased initial acceleration. Since the stock carbs and arrestor are easily capable of delivering enough fuel and air for the desired 6800 – 6950 rpm peak, the improved rpm ability of bigger carbs would be “the answer to a question that is not being asked”. We do not intend to say that “high performance carbs are no good”. However we will say that they are “very” questionably worthwhile in a 14.5 application. What is unquestionable, is the significant increase in fuel consumption that most high performance carbs would net.

All this said, There could be merits to a slight increase in the throat sizing of the stock carburetors in a “sport” application. The 40mm carbs on the 782cc models are actually 37.5mm. Group K offers a modification to these carbs to make them “true” 40mm carbs. This slight increase in bore size adds significantly to acceleration off the turns, without causing significant reductions in “signal” or fuel range. The 38mm carbs of the 718cc models can be bored to 40mm as well, however the signal characteristics and throttle control of this setup are not as good the true bored 40’s from the 782cc motors. For 718 owners wanting bigger carbs, we recommend using a set of true-bored 782 cc carbs…they bolt right on to the stock 718 manifold and flame arrestor.

Rotary Valves – There are a few aftermarket rotary valves available. Despite this, we have consistently gotten the best overall performance and wear with the stock rotary valves.

One important issue connected to the rotary valve is that of crankcase wear at the valve face. On high hour engines (200 – 300), the rotary valve disk can significantly wear the crankcase faces it comes in contact with. There is plenty of material in this area of the crankcase to re-machine a fresh surface, but the machining procedure requires great accuracy. Most dealer service departments that see a worn surface in this area of the crankcase will tell the owner he needs new crankcases ($400 – $500). At Group K we commonly perform this machining repair process on racing versions of the 718 and 782 motors (for $130).

Exhaust System – Here too, there is a wide range of aftermarket exhaust systems available for the 718cc and 782cc pwc models. Most of these systems are intended for racing use on lightweight models of the 718/782 pwc’s. However, like the aftermarket carbs, the primary intent of these systems is to dramatically increase peak rpm…not a need on the 14.5. Even “sport” use owners would not be happy with the noticeable loss of low-end drive that comes with most of these aftermarket systems. We strongly recommend against the use of “any” aftermarket exhaust component on the 14.5 jet boats. For the wide rpm range that the 14.5 engines must operate in, the stock exhaust pipes and muffler boxes are very hard to improve on.

Ignition System – The stock ignition systems in the 14.5’s are very reliable and effective systems that should not be tampered with. The rev limit of the 718cc version is about 6950 rpm, while the 782cc versions are set at about 7100. These are reasonably safe peak rpms for both engines to operate at. Since the stock pipes are tuned for maximum hp slightly below these rpm limits, there is no logical need to increase the rev limit of the stock ignitions. We recommend against any modification to the electrics of the stock ignitions.

When the engine revs approach the limiter of the ignition, the engine will make a slight “missing” sound. In many cases you may only experience this sound when negotiation a hard right hand turn. However if you begin to notice this “missing” in a straight line on smooth water, you should probably consider inspecting the condition of the wear ring in your pump. If the wear ring is in good condition, you should consider slightly increasing the pitch of your impeller. This is a service Group K can provide.

Cylinder Porting – In the past, cylinder porting has received an undeserved reputation as a modification that harms low end power and reduces engine life. This may be true for poorly executed port work done by folks with little experience. However quality cylinder porting can be tailored to create an accent toward any kind of horsepower need. Our cylinder porting modifications for the 14.5 jet boats carries an accent towards strong low to middle range power to help drive the boat off the turns. An unintended benefit that comes along with this porting is a 100 rpm increase, and the added torque to pull a slightly steeper impeller pitch. To assure that the modified cylinders will have the correct compression ratio and deck clearances, we typically modify the cylinders and cylinder head as a matched set.

No other modification nets a bigger increase in overall acceleration on the 14.5 boats than the cylinder porting. At the same time, the porting helps to significantly improve “cruising” fuel range. Our 718cc test-boat turned 6800 rpm at full throttle with the stock cylinders. After the porting work (and matching head modification), the same boat turned 6920 rpm at full throttle, and 6800 rpm at half throttle. The ported engine could now cruise at half throttle running the same speeds as running full throttle with the un-ported cylinders. The fuel range improvement of the ported cylinders is considerable.

All Sea Doo cylinders come from the factory with virtually no port chamfering at all. This absence of chamfers causes premature and excessive wear on the rings and pistons. Careful chamfering of all the ports is also included in our cylinder porting upgrade. All cylinders are also honed after the port work is completed.

Reliability Issues – 718cc/782cc engines that are new, or have relatively low hours, can easily accommodate the slightly increased loads of these performance modifications (your Sea Doo dealer can plug into your electrics and tell you how many hours are on your engine). However we realize that there are plenty of 14.5’s out there that have “lots” of time on the motors (250 or more hours). While these high hour engines “might” be able to continue to operate okay in stock form, the added loads of better props and more power can sometimes induce the failure of an unrelated “time worn” engine component. A normal rebuild, done by a qualified shop, can easily restore your boat to full longevity strength. However owners with “median hours” 14.5’s can take some preventative measures. They are as follows.

Air Leaks – The lower end of these motors must be airtight enough to hold 8 psi for about 10 minutes. Any leak that exists can allow raw air into the motor, to cause intermittent lean conditions, and possible piston scoring. The most common points of leak are at the rotary valve cover/inlet manifold, the crank seals, and the center case split (behind the starter). Also inspect the inlet manifold for any fractures. These leaks are easiest found with a pressure test kit (available from Watercraft Connection 503-232-2026). We strongly recommend that any 14.5, with over 200 hours, be pressure tested before the installing any performance equipment.

Crankshaft – The crankshaft in the 14.5’s may be unfairly characterized as a weak part…it is not. However it is a part that has longevity limits when subjected to high usage hours or high rpms. If you have any reservations about the condition of the bearings on your crankshaft, get it rebuilt…the investment will be well worth the money.

For customers who desire an engine rebuild, Group K will perform complete short block rebuilds assembled with your modified parts. These rebuilds will include final pressure testing of your engine.

About Strokers – For several years, the IJSBA competition rules permitted the use of stroker crankshafts in machines that used the 718/782 engines. As a result, there are many stroker crankshafts and engines out there. Given this, many 14.5 owners have considered the use of a “stroker” crank or motor.

While these “stroker” engines certainly have the potential to offer an increase in performance, that increase comes along with big losses in long term reliability (of the crankshaft in particular). We consider the longevity prospects of these “stroker” based engines to be so poor, that we will not construct any stroker based engines, nor will we produce a Sleeper kit for any stroker motor.

Big Bores – Big bore kits for racing versions of these engines are quite common. However the long term reliability, in a recreational application, has yet to be proven. To date we have not seen any big bore kits for these engines that we consider to be bulletproof enough for use in the 14.5 boats. We will not perform any of our engine modifications on engines using anything other original equipment Sea Doo piston diameters.

Vibration – One area on the 14.5’s that merits attention is the issue of engine vibration. In particular the 718cc models which are not built with the integral harmonic balancer. Excessive vibration should not be left unattended to because it can prematurely wear many parts of the craft, to say nothing of the increased likelihood of vibrating bolts loose. Even though the engines in the 14.5’s are rubber mounted, there is still plenty of high frequency vibration being delivered to the hull and driveline. There is no way to eliminate 100% of this vibration, but there are a few ways to dramatically reduce it.

Engine Alignment – The engines in all Sea Doo crafts sit on rubber cushion motor mounts. At the factory, each engine is individually aligned (using shims between the rubber motor mounts and the motor bed plate) in each hull to assure center to center alignment between the engine’s crankshaft and the drive shaft of the pump. When these are perfectly aligned, the entire boat operates noticeably smoother at all rpm’s. Among production runs, some motors are better aligned than others. In addition to this, the alignment can be affected by engine removal/replacement, and just plain long term use.

Sea Doo makes an engine alignment tool that allows technicians to precisely re-align the engine in your boat with the pump. This procedure is not quick or easy, but it can pay big dividends in reduced vibration.

Fluid Balancers – A company called Vibratech manufactures fluid balancers for the 718cc/782cc engines. This balancer replaces the stock “PTO” (the pto is the flywheel threaded on to the rear of the crankshaft). Here again, the installation of this balancer is not easy, since it requires removal of the engine. However for the owner who wants to maximize the smoothness and long term wear of the 14.5, this balancer is a wise choice.

About Fuel Octane – When modifying the engine and pump for higher performance, the internal engine heat being generated is slightly increased. These slightly higher engine temperatures are not a problem during casual or partial throttle use (cruising, towing, etc). However during extended high rpm usage’s, this excess heat can mount to a point where it causes a measurable loss in peak rpm’s (and peak speeds).

The stock 14.5 machines are designed to be able to operate on 87 octane unleaded fuel. By simply going to a 92 octane rated fuel, you can significantly reduce the internal engine temperatures, and avoid this power loss. In addition, the higher grade fuels tend to leave fewer carbon deposits in the combustion chamber.

We strongly urge any 14.5 owner, who modifies their boat, to use only 92 octane fuels. The slight increase in cost is well worth the insurance against engine overheating.

About Instrumentation – It’s virtually impossible to find a speedometer that is durable and accurate enough to be effective on the 14.5’s. However very accurate, and inexpensive, digital tachometers that can easily be fitted to the 14.5’s. For all intents and purposes, a tachometer is every bit as good (if not better) than a speedometer. A digital tach allows you to monitor the consistency of engine performance, and allows the driver to more easily diagnose operational problems.

The digital tach best suited for the 14.5’s is the Tiny-Tach. These tachometers are very durable, accurate, affordable, and waterproof. In addition, the Tiny -Tach has an included hour meter. We strongly recommend a Tiny-Tach digital tachometer/ hour meter for every 14.5 owner.

Assembly Information – All Group K kits are accompanied by a step by step instruction pamphlet that outlines the assembly, break-in, fine tuning, and maintenance of your kit. For any further questions you may have regarding your kit, you’re welcome to contact us directly for assistance.

The teardown and assembly of the stage 1 setup can be done by owners who have basic tools and basic mechanical skills. The Stage 2 kit requires the removal of the cylinders (and possibly the carburetors). Because of the added linkage hardware that operates the carbs (and the exhaust valves of the 782) , this teardown and re-assembly requires a higher level of mechanical ability and expertise. If you doubt your ability to correctly reassemble these components, we recommend to have the job done by an experienced technician.