Seeking advice for a Rotax 581

[Machack]

Hello all,

I just joined this forum, so I am looking forward to getting some insight for a project I am working on. My father gave me his derelict Sea Doo from 1987, which has not run since approximately 1999. Before it went to bed, he had it modified by Decker Racing in Marshfield, Wisconsin, which included boring out the Rotax 581, adding dual Mikuni carburetors, and a plethora of other modifications. It seemed to have gotten a little water into it at some point, as the pistons, not the cylinders, are slightly scored. I have removed the engine from the vessel, and have nearly completely disassembled the motor. My main question to those who are more familiar with this engine than I; what should I replace or check while I have the engine totally disassembled? Im experienced with other vintage boat engines, but the Rotax is a different animal. I am mostly concerned with little engine-specific things that should be checked while its in pieces. Any advice is greatly appreciated!

 

[Venturian1]

581? Are you sure its not a 587?

 

[Machack]

My dataplate says "580.8cc" and doesn't have a model number, so I took that to mean 581. I could always be mistaken.

 

[Venturian1]

The last two digits of the VIN (HIN) should be the year. On seadoomanuals.net the year for the manuals start at 1989. Good luck!

 

[mikidymac]

Check clearances and replace all gaskets and seals.
You will have the Yellow 580 aka yellow 587, same thing. First year was 1988.

Seadoo Source....
Although I don't recall ever seeing one, Sea Doo first "arrived" in 1988 with a unique hull design and seat that opened different than the 1989 and up. It was equipped with the 587 Yellow motor which was in all Sea Doos from 1988 to 1991. The SP is technically a 2 passenger machine although that hull was pretty tippy with anything more than a couple kids onboard. I would guess not many were sold since they're pretty scarce compared to the 1989 SP. The person below sent me the pictures and info on his really nice 1988 so I added it below. If anyone else has one of these, info on it, or pictures of them, I would love to add it to this page too!.

"You stated that you had not seen and did not have a picture of a 1988 first year Model 5801. I was a July 1988 purchaser of the first year model and still have it. It has not been stored and has been used every summer since 1988. It is original (except for batteries and impeller) and the engine is completely original (rings, pistons, etc.). I have used BRP two stroke oil exclusively and the heads of the pistons are clean and carbon free. The 1988 had a rear hinged seat with piston support that opened clam shell style rather than coming off like the 1989. I have attached photos taken last year of the 1988 and the engine. It is literally showroom."

 

[MAL]

Hello all,

I just joined this forum, so I am looking forward to getting some insight for a project I am working on. My father gave me his derelict Sea Doo from 1987, which has not run since approximately 1999. Before it went to bed, he had it modified by Decker Racing in Marshfield, Wisconsin, which included boring out the Rotax 581, adding dual Mikuni carburetors, and a plethora of other modifications. It seemed to have gotten a little water into it at some point, as the pistons, not the cylinders, are slightly scored. I have removed the engine from the vessel, and have nearly completely disassembled the motor. My main question to those who are more familiar with this engine than I; what should I replace or check while I have the engine totally disassembled? Im experienced with other vintage boat engines, but the Rotax is a different animal. I am mostly concerned with little engine-specific things that should be checked while its in pieces. Any advice is greatly appreciated!

You need to check the inner crankshaft seals and all the bearings on the crankshaft, but you will need to do a pressure test on the engine when it is assembled to make sure that it is not leaking. If the inner crank seals are leaking you will need a new crankshaft. If there was water in the engine then you may/will be better off replacing the crankshaft anyway.

 

[MAL]

Here is a video of a 717 rebuild It is not the same engine but it is very similar.

He does a better job of showing how to pressure test an engine in this video of a 787