1995 SeaDoo SP 587 white engine low compression.

[bmongan]

Hello everyone. I am having trouble with my 1995 Seadoo. Last time I used it about 3 weeks ago it seemed to run fine. When I got back to the house with it I flushed the motor using salt-off, and it ran fine. I just went to winterize it and I could not start it. It seemed to have no spark, while I had the spark plugs out I checked the compression. Both cylinders were reading 60psi. I was thinking it was odd that they were both so low, so I bought a new compression tester and got the same reading. I checked the compression when I bought it and the reading was 130psi in both cylinders(3yrs. ago). I changed the coil and now have spark but it will not start. Is 60 psi too low to even fire up and is there any thing besides the piston, rings, and head gaskets that would cause such low compression. I use very little oil each season but read on the forum using the Seadoo oil and pump should use little oil. I probably use 20 gallon of gas a year and about 1/2 quart of oil. I am thinking of pulling off the head to see the cylinders. I am a machinist so boring and honing the cylinders are no big deal for me. If anyone has any thoughts or input I would greatly appreciate it. Thank you in advance.

 

[statikuz]

Super dead battery - enough to crank but not strong enough to get good compression? Just a thought since it ran well recently.

 

[bmongan]

Thank you but new battery and cranks real good.
Just a side note last time I used it, it was rough starting but I just chalked it up to sitting and not using for a few weeks.

 

[Joey White]

You should have at least 120 psi in each cylinder, if not you might've blown a piston from running it too lean, it doesn't hurt to check by taking off the head to see the conditions of the pistons.

 

[etemplet]

Even at 130psi there were worn and damaged parts in there. I bore mine long before 130 but that's me. LOL

 

[bmongan]

So I tore the head off today. The cylinders had very little wear. I could still see the cross hatch marks from honing, they were faint but visible. So I am thinking it was just the rings worn causing the low compression.
With that being said I think I have to change to the heads anyway because the O-ring groove around the water jacket was blown out in areas. It would probably work fine with if it had regular gasket but it will not hold the o-ring in place.

 

[etemplet]

Got any pictures of the head?

 

[bmongan]

 

[bmongan]

 

[gazzaskirepair]

Do a top end overhaul but you have to find some good cylinders if the seal ring groove is damaged
I don’t know if they weldable
Check with Shopsbt.com

 

[bmongan]

Thank you

 

[gazzaskirepair]

Thejetskistore.com

Will MAY offer you better prices on SBT items and may have some second hand cylinders
Speak to Dave and say Gary recommended

 

[etemplet]

Hmmmmm.....

 

[bmongan]

I purchased some nice used cylinders. They were std. size but a little worn. I am a machinist so I machined the cylinders until they clean up nicely. Standard bore is 2.9925 My cylinders cleaned up at 3.0025-3.003.
My question is does anyone know approx the measurement of WSM .25 over size piston. WSM could not tell me. I am trying to decide which size I should order. .25mm or .50mm. If I could get away with .25 and have to swipe the cylinders a little that would be great, but if they are already to big for .25mm o/s then I will order .50mm

 

[gazzaskirepair]

You are on the limit of .25
If that’s the final dimension you machinist has given then .25 is ok but if you don’t intend on doing another top end in the life of the ski then get .5
.25 is 10 thou oversized so add 10 thou to your measurement

 

[bmongan]

You would think WSM would be able give me a number. I am sure they have them machined to a specific size and they have a tolerance. I was looking for a range. I guess I will have to order .50 mm to play it safe. Anyone have a preference WSM or SBT and why.

 

[mikidymac]

I prefer WSM. I have installed a lot over the years without a single issue. As far as SBT I haven’t seen a single part from them that was good quality.

Also PWC Muscle gives forum discounts on WSM parts.

 

[bmongan]

I prefer WSM. I have installed a lot over the years without a single issue. As far as SBT I haven’t seen a single part from them that was good quality.

Also PWC Muscle gives forum discounts on WSM parts.

Thank you for that info. I will look into that. Quality is important to me.

 

[mikidymac]

The best quality is OEM pistons then Pro-X then WSM then SBT in my opinion. Wiseco are good but only if your machinist knows the correct setup clearance because it’s different than all other pistons.

 

[etemplet]

My question is does anyone know approx the measurement of WSM .25 over size piston. WSM could not tell me. I am trying to decide which size I should order. .25mm or .50mm. If I could get away with .25 and have to swipe the cylinders a little that would be great, but if they are already to big for .25mm o/s then I will order .50mm

All I use is WSM pistons. I don't do .25mm because that isn't enough to clean up or work with if you have some uneven wear or other issues. Isn't that stupid that WSM can't give you a piston size !! I've bored a number of cylinders for the Seadoos so much that I know the sizes. LOL When you get the WSM's you're gonna need .0045" clearance minimum. I think their rings always have a larger end gap but not by much. Good Luck.

On a side note, I bore my cylinders in the lathe using a mandrel


.

 

[bmongan]

Hello everyone. It has been awhile, but I bought 2 nice used jugs honed them .50mm oversize. I bought the WSM top end kit. I just assembled it today, and all went good. My compression was 160-165 in both cylinders. I will include some photos. Upon disassembly I noticed my old cylinder had very little wear, my problem was the bottom ring on both piston was stuck in. Now my next question is for the break in, should I mix oil in with the gas along with the injector oil? Thank you for all the help.

 

[mikidymac]

Make sure you chamfered the ports really well or you will snag a ring.

And yes you should premix at 50:1 for the first tank of gas in addition to the oil injection.

 

[bmongan]

Make sure you chamfered the ports really well or you will snag a ring.

And yes you should premix at 50:1 for the first tank of gas in addition to the oil injection.

Thank you for your response. I chamfered the ports the ports good.

 

[bmongan]

Hello, Can anyone tell me if the shims under the motor mounts are important. Mine were just crumbling and falling apart. Can I just shim the top of the mount or does the bottom shim serve any other purpose? Basically I was wondering if I could bolt the motor mount directly to the hull and only shim the top. Thank you for any info.

 

[mikidymac]

Yes you can shim just the top but it will take more to get it aligned. The lower ones are to get it close and the top ones are to fine tune.