Hi All,

I have been searching and searching for some help on the Seadoo Forums and can't seem to get any help so I am hoping you guys might be able to help.

Boat is a 01 Seadoo Utopia 185 with the 200hp Mercury Optimax M2 Jet Drive. I bought it from my boss for $500 cdn it's worth north of 10k here. It was one of 6 boats that he owned, it was NEVER used just sat at the dock and was winterized/de-winterized every year by a marina and prior to me buying the boat it had sat in storage for 2 years at a marina. When I bought it they de-winterized and water tested it.

I used it one day, ran great but it was doing something funny while going at a steady speed the engine's tone would change, like it would bog down for a bit then back to normal then bog a little then back to normal. You could hear it and also feel it lose speed/power a little but it still seemed to work good, was getting 50mph which is it's top speed.

Second time about a week later I got out, run it for 5 minutes and it dies instantly, It cranks but won't start. I take it out of the water and bring it to a Seadoo/Mercury dealership they find it was just a fuel pump fuse but also notice that Cyl 5 has low compression, won't read above 100psi. Their suggestion is to buy a new block from Mercury which runs about $5500 + all the labour to rebuild it....does this seem right?

I find this a bit odd since it was running good the last time so I take it out on the lake yesterday and sure enough, after idling/going slow for a bit I take it up to half throttle, it ran good then I heard that same noise but this time, it didn't go back to normal. As well, I couldn't go more then 30mph so I brought it back to the cottage for fear of doing more damage

**Disclaimer** I am a car guy, I've rebuilt car engines, did engine swaps, electronics/EFI upgrades etc. very handy with cars but never worked on a boat, this is my first boat and the wife only let me have it because it was so cheap for what it was worth, we thought we were getting a crazy deal not knowing of course we would have this problem. My boss never used the boat, it was parked for 2 years so it's not like he was trying to pull a fast one on me. Now my wife is ok with me fixing it if I can get it done as cheap as possible**End Disclaimer**

So, here are my questions and options that I see:

1-Could they have done the compression test incorrectly? Is there a how-to somewhere to help with doing this? Even if it's just another Merc motor not this one specifically?

2-Is there anything I can do while the engine is still in the boat in hopes that it's something other then the engine? Could it be spark plugs/wires? I keep hearing about "clipping" plug wires when doing a plug change?

3-Is there something else that would cause low compression? Something I should look for?

4-Can I rip it apart in the boat and replace the piston rings like you would do on a car? Or does the engine need to come out completely and taken in to be rebuilt?

5-I keep reading about "Powerhead" is this a complete assembly that I can take out and get that rebuilt without having to pull the whole engine?

Just looking for advice from others who seem to have a lot more knowledge on fixing/rebuilding Mercury engines rather then paying a marina to put in a brand new engine.

Please help save my summer!!

Thanks everyone!
Jerome