1995 SeaDoo Sportster Re-engining

[randyhig]

I bought a 1995 SeaDoo Sportster with a locked up engine. I tore the engine down and found the crankcase was full of sludge and rust. The block is junk. Anyway, this boat only has 73 hours on it and is in perfect condition including the electrical.

I am looking for a donor jetski with a rebuildable engine and for other parts, but was wondering if maybe I couldnt go to a bigger engine.

From the schematic, The ignition module is external to the microcontroller. I dont see any real engine management except for safety kind of stuff (Revs, overheat, gauges). The microcontroller does take some critical inputs such as start/stop, ignition switch, safety switch, neutral switch. Etc. But I can work around that.

Anyone have a suggestion for an engine swap that would push up the horsepower and fit without engine mount or pump modifications? It would need to be an engine that does not require emissions control.

Thanks
Randy

[Technical Support]

Re: 1995 SeaDoo Sportster Re-engining

If the boat has a 657 then you could go up to a 720 engine and use all the electronics from the 657. 787 and 951 engines use completely different items and will not interchange.

[randyhig]

Re: 1995 SeaDoo Sportster Re-engining

Yes. The boat had a single 657x. I tore the motor down. The crankcase was full of grimey gunk and rust. it looks like it was flooded with water and improperly "pickled". The case came apart without breaking any bolts.

Can the case be polished and saved or is it junk?

thanks for the tip. It appears the 717 motors are much more plentiful than the 657x. And you can get a much newer block than the 1995 657x.

Randy

[Technical Support]

Re: 1995 SeaDoo Sportster Re-engining

717 is a good choice if you can do it cheap, if not just rebuild the 657x it too is a good engine. Sounds like the case is good to re-use.

[randyhig]

Re: 1995 SeaDoo Sportster Re-engining

Hello again: Recall, I have a 1995 SeaDoo Sportster jetboat with a single 657x engine (per the lable on the mag housing). I subsequenty bought a 1995 SeaDoo GTX with a 657x engine for parts (again per the lable on the mag housing). both engines are out and torn down. When I went to compare parts, the GTX crankshaft compares to the the 657x cranks on this web site. The Sportster crankshaft matches the 717/720 crank on this web site. The crankcases are clearly different. The Sportster only has 72 hours on the clock and i'm confused as to what's going on.

What are the other specifications of the 717/720 engine I can look for to confirm the engine out of the Sportster is really a 717/720 (not a 657x)?

[randyhig]

Re: 1995 SeaDoo Sportster Re-engining

Disregard my request above.

I found the bore specs for each motor. The engine out of the Sportster has an 82mm bore with a 717 crankshaft/case and the GTX has a 78mm bore with a 657x crankshaft/case.

Even though the Sportster only has 72 hours on the clock, I guess someone already switched long blocks from a 657x to a 717 (but reused the mag housing)

[Technical Support]

Re: 1995 SeaDoo Sportster Re-engining

Yep we have seen that before