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There is absolutely no doubt that the new 4-stroke offerings from the PWC makers are (and will continue to be) very quiet, comfortable and smooth running machines.
Unfortunately, along with all this wonderfulness comes some negative baggage. First and foremost, these are the most expensive pwcs ever made, and will unlikely get cheaper as more bells and whistles are added to future models. Along with this, these new 4-strokes are easily among the largest, heaviest, and mechanically complex PWCs ever made. The 4-stroke engine platforms need space in the hull for all the running gear (cooling systems, electrical boxes, etc) ….All this extra stuff adds weight. The makers have done a good job of packaging the 4-strokes very nicely…. But at the end of the day this added weight makes these PWCs more like a boat, and less like a traditional lightweight PWC. No doubt lighter designs may eventually come forward…. However that technology will very likely add even more to the already heavy price tags. For the foreseeable future, no 4-stroke PWC will be light enough or short enough offer the riding experience of a lightweight 1990s stand-up or sport class 2-cycle.
"Do the 4-strokes have any "negatives" for new owners??"
The high technology used in the new 4-strokes are both their best features.... and their weakest links. These overhead-cam, multi-valved, electronically-managed engines have many times the moving parts of a 2-cycle. All those extra moving parts carry added possibilities of wear and possible failure. The 4-stroke engines used in most PWCs are based on sportbike/superbike engines. These engines have a good reliability record in motorcycles where the vast "majority" of operating time is at lower cruising rpms against the very low rolling and wind resistance that a street-bike offers. However there is little data on the long term wear of these engines being operated at peak-rpm/full-load for extended amounts of time (as PWCs are routinely run) against the non-stop heavy load resistance of the hull/water contact surface area presented by a large pwc.
Despite all that, the greatest likely-hood in reliability risk factor for a 4-stroke PWC is that of significant water exposure. For a long list of reasons (none good, but all real) It is very routine for PWCs to get completely submerged ... aka "sunk". When this happens to a carbureted 2-cycle PWC, it is routine to remove the spark plugs, clear the engine of water, and re-fire the boat to go enjoy the rest of your weekend. When you submerge (or flip over) your 4-stroke PWC, there is a great risk of water reaching the interior of the engine. If this happens, an unwary operator can very likely presume that all is well...a touch the start button to get under way. If "any" water has passed the air inlet to the cylinder, a cylinder will be hydraulically locked by the starter... and instantly bend a connecting rod. Even if the rider is wary enough to not touch the start button, the ingested water must be cleared from the motor and oil very quickly to avert damaging the many internal lubricated moving parts of the engine. Since sport-bikes never get exposed to significant water, none of this is an issue for them.
Most PWC enthusiasts are accustomed to performing affordable modifications to their 2-cycle pwcs that net significant improvements in performance while having a negligible effect on longevity. They are also accustomed to these kinds of parts and modification being readily available… even for newer models.
For the first few years that the 4-strokes were been available, and was little more than incidental “knick knacks” available to increase their performance ….. and there are a couple of very good reasons for this. There are a few shops offering more exotic modifications (aftermarket superchargers, re-mapped ECU boxes, etc). However there is little info (and much to be learned) about the long term reliability of these mods in a pwc application.
Most of the 4-stroke PWCs have their designs based on popular street bike engine platforms. To be sure, there is no shortage of folks who have lots of experience modifying street bike engines. In addition, there are many folks out there with lots of 4-stroke turbocharger/supercharger experience. While all these folks have lots of skill and experience, there is great reason to question whether that skill and experience will have any meaningful value when translated to 4-stroke PWCs …. Here is why.
Most of the high performance engines used in high output motorcycles and turbo/supercharged automobiles make impressive horsepower numbers “for their use application”. These engines are typically run at top gear at peak rpm for no more than a few seconds at a time. High performance PWCs are routinely run non-stop at peak rpm/peak speed for 10-15 minutes. There are “no” normally aspirated super-bikes or street-cars that are run at peak rpm in high gear for 15 minutes …. Mainly because there isn’t that much open-space anywhere on earth. If “everyday pump-gas” super-bikes were run routinely at peak rpm in high gear for 15 minutes (as PWCs are), their tuning would be much different, components be more heavy duty, and power output likely “alot” less.
The best known venue where multi-valved overhead cam engines are run at peak rpm in high gear for more than a few moments, is in open wheel auto racing (IRL,CART, etc). Of course, these race machines make huge power numbers. However, the life span of the (extremely expensive) moving parts in these engines is rated in operating minutes…not hours. There are very few pwc owners that will be willing to embrace the costs and maintenance schedule of such a highly tuned machine.
The second reason for the absence of 4-stroke pwc tuning parts is much more a matter of practicality. There are a few tuners who have found “significant” increases in engine power (and speed) with modifications that are relatively minor (increasing boost, rpms, etc). Sadly, most of these mods net their power gains by “greatly” increasing the stresses on all the existing moving parts of the engine. The PWC makers have made their 4-stroke engines as light as possible in the interest of weight… and few parts are made “more heavy duty” than needed. .Since most of the moving parts are not made for extremely high output or long term stresses, the risk of a moving part “breaking” in a modified version is greatly increased. Unlike a failure in a 2-cycle, there is seldom a “small” failure of a moving part in a high output 4-stroke. In a high output 4-stroke engine failure, moving parts often “tangle” with each other, snowballing into a catastrophic event that scraps a big collection of expensive pieces. In such an event, the pwc owner might understandably look to the folks that sold him the modifications for some warranty or reparation. From a business standpoint, to cover the cost of the engine parts that might be destroyed in such a failure would be a prohibitively high cost.
Sadly, most of the existing 4-stroke (motorcycle/automotive) aftermarket is dedicated to lighter weight and exotic material components … not heavier duty ones. Convincing a pwc owner that he may need $2000 worth of heavier duty parts so that he can safely use a few performance enhancing parts is a very tough sell….. So tough in fact that very few performance shops have succeeded in securing that market. For sure there will be available performance benefits from “low risk” parts like props, ride plates, etc. But we suspect it will be a long time (if ever) before “horsepower increase” products for 4-cycle PWCs will be considered “low risk”.
In time, there will most certainly be some effective high performance modifications for 4stroke PWCs. However at the end of the day there will big two big truths they will have to live with. 1 - More moving parts means more parts to wear out and potentially fail, and 2 – When failures of those parts take place, the residual damage will usually be very extensive…and very expensive.