1985 force 85hp low/no compression

LayinLo

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Aug 15, 2012
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I recently purchased an 85 bayliner capri 1600 with a force 85hp. Motor ran when I purchased boat. I have since restored the entire boat, removing motor to do so. Upon reinstalling motor, it wouldnt start. Originally a fire issue. Replaced the coils, cdi box, stator, trigger, and replaced all carbs as well. Have great fire at this point. Still wouldnt start. So I figured it was a fuel problem now. I swapped fuel pumps with another motor. With the oulet hose off it will spray fuel when cranked. Bowls fill when pump the bulb on fuel line, resulting in a solid bulb. Still no start. Did a compressikn test today, cyl 1 is 50, cyl 2 is 52, cyl 3 wont register a reading on the gauge. I pulled the head. Head gasket looks great. all pistons look good, no detonation, scoring, cracks, ect ect but cyl wall is scored on #3. Curious what my next step needs to be. Can the walls be honed slightly? The scoring isnt very deep but its definately there. Im an ase certified auto tech at tires plus and I just hate the thought of having to take it somewhere to have it fixed. Curious if its something I can fix myself or if its worth the costs to have a shop fix it. Any guidance at this point would be extremely helpful.
 

foodfisher

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Feb 18, 2009
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3,756
Re: 1985 force 85hp low/no compression

Surprised at the lack of replies. I would have rechecked the comp. numbers prior to head removal with a different tester, but, your description sounds like stuck rings. A decarb might fix that after you put it back together. Seafoam deepcreep soak, some like Marvel Mystery oil, Soak them rings
 

LayinLo

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Re: 1985 force 85hp low/no compression

Surprised at the lack of replies. I would have rechecked the comp. numbers prior to head removal with a different tester, but, your description sounds like stuck rings. A decarb might fix that after you put it back together. Seafoam deepcreep soak, some like Marvel Mystery oil, Soak them rings

so just with head removed put some oil in cylinders? how long should i let them soak? im sorry im very new to boats so im not sure what you mean by decarb? could someone run thru the process of trying to get these unstuck before i spend twice the boats worth on motor work? thank you
 

foodfisher

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Feb 18, 2009
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3,756
Re: 1985 force 85hp low/no compression

The decarb process is described in the "engine frequently asked questions FAQ" forum, second page. It would require you to reassemble the engine though. Some more experienced motorheads might chime in to help, considering you've already pulled the head.
 

LayinLo

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Aug 15, 2012
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Re: 1985 force 85hp low/no compression

The decarb process is described in the "engine frequently asked questions FAQ" forum, second page. It would require you to reassemble the engine though. Some more experienced motorheads might chime in to help, considering you've already pulled the head.

ok thank you foodfisher i will check into decarb, but if there is any more information i need to know feel free to let me know lol im all ears at this point
 

emoney

Commander
Joined
Jul 19, 2010
Messages
2,551
Re: 1985 force 85hp low/no compression

Are you confident in your tester? Seems odd that you'd lose compression in all 3 at once. How long did it sit during the makeover? Post some pics of the cylinder walls while you're at it.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
18,183
Re: 1985 force 85hp low/no compression

The comp #s are way off.
Get another tester.
You remove all the plugs during the test?
They sell a product called Power Tune,by Mercury or Seafoam.
I like Power Tune.

Get the head and block all cleaned up.
Install a new gasket,or use silicone to reuse the old.
Get a new gasket for final assembly!
Do another comp test.
Post the results.
If the results are the same then a rebuild is in order.
Low on 1 then the power tune comes in to play.
Tilt the motor up,remove the plugs and spray a lot of PT in the cylinders.
Let it set for a couple of days adding more PT everyday.
Turning it over as you go.

Try to start it use starting fluid if needed.
I don't usually recommend starting fluid but your probably gonna be rebuilding and way.
Do these things and post the comp #s
Make sure you ground out the plugs if your using the key to turn the motor over.
Try to use a jump box or jumper lead at the solenoid.
 
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