1990 Force 90hp NO compression cylinder 3

[Mackus84]

3rd owner of a 1990 Bayliner capri bowrider. Had a few long periods without use. Got it from my brother recently and got it up and running and did some other work as well. Have had it out on the lake a few times recently, and the boat seems to be down on power. Has trouble getting on a plane with any more than myself in the boat. Once its up on plane it seems to run well, about 30 mph at WOT at 5300 rpms. Ive went thru the link and sync a hundred times, carb adjustments, and just couldnt figure out why i couldnt get up on plane, put a brand new 13.75x 15p prop on it. Still, planing issues, so today i decided to grab a compression tester, grounded out the plug wires, removed all plugs, tried with no throttle and WOT and I got 110lbs in cylinder #1, 105lbs in cylinder 2, then i was actually surprised when i got ZERO on cylinder 3!! Aside from being down a little on power on acceleration, all else seemed fine. Im thinking i have stuck rings on that cylinder from the periods of sitting without use.The plug does have some carbon but not as much as the others (brand new plugs) ANY thoughts or recommendations on what to do next? How to unstick the rings?

 

[racerone]

Doubt it is a " stuck ring " problem when they read 0 compression.----Take the cylinder head off now.------Lucky you if it is a blown head gasket.----Myself I think it is tear down / rebuild time.

 

[Mackus84]

Yeah, after more thought, i think you're right. Got two problems though, #1 there is a snapped off bolt on the head i just noticed, (didnt think it had ever even had a wrench on it so no clue how that happened) and #2 i cant find a rebuild kit anywhere for this motor. Does the whole thing need to be rebuilt, or just that cylinder? Thinking im just gonna sell the boat as is and let someone else deal w it

 

[jerryjerry05]

No kits that I know of.
Usually 1 cyl is affected and buying parts for 1 is a lot cheaper.
Get the head off and see what's wrong??

Might just be a gasket?
Could be a bad piston/rings.

These motors are fairly easy to rebuild.

You just need a factory manual and ask questions.

 

[Mackus84]

Thanks Jerry. Thats what i was afraid of. Found plenty for 1991 and up but none for 1990. Gonna have to look around and cobble some parts together if the pistons done

 

[Mackus84]

Also, i CANNOT find a factory service manual for this motor. Only Online Seloc. Or generic manuals for multiple years

 

[kbh121956]

Do a search on EBay for your service manual as they come and go. Try Franz Marine for your parts.

 

[kbh121956]

Also marine engine dot com has your piston and rings.

 

[Mackus84]

Thanks bud. Yeah i also found them on Offshore Marine, which isnt too far from me. Gotta get the head off first, theres a snapped bolt in there and Im a little scared to snap any more

 

[jerryjerry05]

The 90 and 91 manuals are real close.
The 90 year had 2 different models "A@B with different part #s. and the pistons were different sizes.
The 91 manual has all the rebuild info.
You'd have to figure out if yours is an A or B model..
Then use the corresponding sizes for your pistons etc.
You can use a 91 manual if yours is a B model.

 

[Mackus84]

How do I find know if its and A or B model? I did see a couple "A" model manuals

 

[jerryjerry05]

Any stickers on the transom?
Pull the head and measure the piston.
3.359-3.370A model prior to 1990B
1990B 3.305-3.309

Bore and stroke:
prior to 1990B
3.3125X2.87
84.2X 73.1mm
1990B model and later
3.3750X2.87
85.7X73.1mm

 

[Mackus84]

My motor is 906X90C. Only sticker I see. Still working on getting the head off bc of the broken bolt. Supposed to have someone come today and weld a head on the broken bolt. It was broke right at the head cover so I was able to pop the cover off and it gave some bolt to work with. Im pretty positive its a "B" model, bc when I look up the oem piston part # it comes up as as the larger one 3.37 etc...

 

[Mackus84]

Ok, Ive found 1990 "A" model manuals, Ive found lots of 1992 manuals and other years, Clymer, and Seloc, but absolutely ZERO for "B" models or 1991 models. Im about to just get the clymer or seloc manual. Id rather have the factory manual, but i cant find one anywhere

 

[jerryjerry05]

http://www.boats.net/parts/search/Merc/Force/1990/H0906X90C/parts.html
That's a link to your parts.
You have a C model.

202032474344 e-bay this would work.
But at $50????​

 

[Mackus84]

That link doesnt work, also, i found that same "A" model book on ebay for 17 bucks. Not in as good of shape, but its all there

 

[jerryjerry05]

Buy!!!!

 

[Mackus84]

I did haha. Itll be here in a few days. Michigan to Florida

 

[jerryjerry05]

Where in Fl?

 

[Mackus84]

Im in Lakeland. Smack in the middle off Tampa and Orlando.