Don't know the Yamaha product but SeaDoos use small 1.5L Rotax which is a German-design & manufactured product. They are actually used (and originally designed for the light aviation industry). One thing they all have in common is that they are all small displacment / high revving and seem to be running on the edge the whole time. Smaller boats get one engine. Bigger models just get two of the same with maybe a turbo or some such. They are a suprisingly small unit so removal / re-installation would be much simpler than something with a big V8 in the same void.
I had an '06 16' 220hp SuperCharged / Intercooled. I recall I would have to be running in the area of 3k rpm just to get her putting. Wandering off plane was atrocious. In fact off plane there was no straight-ahead only constant correcting and swerving back & forth. I am told this is common for at least the single engine units. Ironically, once you get used to (not hard to do) the reverse power opposite of a prop boat they can be very maneuverable around the dock. They can spin like a top in thier own lenght. In neautral and because of direct drive to the impellar (always turning) they hover in place rather than drift around.
I have never piloted a twin so that may be quite a bit different as far as the wandering issue.
I do not have the luxury of year round boating season so yes, winterizing was required. However with a SuperCharger and Intercooler it was not as simple as it could otherwise be.
Intercoolers (if equipped) are a rad cooled with water inside the intake manifold by the illustrations I have seen - they are basically heat exchangers so I have concerns where the water could go if your IC develops a leak. Into the cylinders perhaps? Eeek. Speaking of which ask about flushing. Even with closed loop you had to flush for the exhaust cooling etc. With a SeaDoo NEVER have flush water running without the engine running. It can (has on some models) backed up into the cylinders. ByeBye crank, connecting rods and pins, valves etc.
Yes, they have rediculous holeshot and accelleration.
In at least the SeaDoo product line (I suspect the others as well) they have the option of providing a second user a learners key which limits the RPM and does something to the ignition timing thus dramatically kills the power - a very nice feature if you are permitting your kids to use it and have some doubts in thier responsability. They will get on plane and maybe a bit faster but not a whole lot more than that.
My gripe is in the cost of maintenance (fuel useage I felt was quite reasonable in a single) and the spartan accommadions (relative to prop boats) for the dollar. SuperCharger for mine would be a $2500 -3000 repair and I understand they could be easily blown if the boat came out of the water (such as jumping waves and with shallow V (?) in the hull this is easy and sometimes unavoidable). I have my suspicions on the expected lifespan of an engine run on and off 10-12k rpm all the time. Also be aware that 220Hp in a jet drive is not the same as 220hp in a prop boat. Common belief is that you lose +/- 20% of your HP from a prop to a jet but then the jet boats can be lighter.
The shallow draft is a bit of a farce in a sense. Up side you will pass over a submerged boulder on plane if it is only several inches under water. Very cool and very true. But be carefull in assuming that means you only need a couple of feet of water to run 'em. Dealer warned me - "punch it in shallow water and you willl suck a rock the size of a grapefruit off the bottom". Not a big problem - it won't go through the intake. But all the little stones around it will so kiss your impellar, wear ring and possibly your jet pump goodbye. You are then in the same position as replacing an outdrive but without the worry at least of a totaled transom like some other poor bugger here is now going through.
I have heard concerns of weeds causing problems and there are a fair amount growing on my ramp. Never had an issue with that. A rope can
really ruin your day but I guess it can on a prop boat as well. Just more of a risk - it's almost gauranteed to cost you a wear ring at the least if a rope goes in your jet - could go either way with a prop. Its also very unlikely you can limp home if a rope or some such goes in your jet unless you are running a twin.
Goods and bads - just like everything else. I came to a FW because I wanted a bigger & more comfortable boat and refused to go to a twin for the sake of a 20 something footer. Double the maintenance, double the heartache AFAIAC. If I am going through the headache of a twin, well I want a Vista out of the deal
Check to see about insurance as well. It was tough where I live and I had only one option and rock or object ingestion to the jet pump was a difficult claim to make as I recall.
The Yamaha looks like a real nice product as Jet Drives go. Accommodations are nicer than SeaDoo at least. You just have to do as I did - consider all the pros & cons and pick what suits your lifestyle & budget best. Mine brought me to FW but make no mistake a jet is a total blast (also).
As for top speed I was told that it is a "gentlemans agreement" in the jet industry that they are intended for family use and despite continued increases in HP they will top out in the neighborhood of 60. They just keep increasing the accelleration (just as dangerous in my mind).
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No they're not an inline 1000cc four stroke eng. Other then that they're basically a large sit in PWC. Yes they do/will suck in stuff if you get too close the to bottom just like PWC's.
