125HP 1987 Force - No Compression

[tluciffid]

Hi all,

I have a 1987 Force 125hp with no compression on cylinder #2. the rest of them test out at 90psi on the nose. thought it was the head gasket was the problem, so I replaced it and to no avail, same results.

Looking at the cylinder heads, there doesn't seem to be any pieces missing, ring looks to be in tact, from what I could see of it. I have not pulled anything else apart as I'm still a novice at marine engines.

History on this motor is unknown, I bought this from a woman who didn't know anything about it. I know that is has not been run in over 3 years.

My biggest question, is it worth it to fix this motor, or just scrap it and get something that won't get me any problems?

does have spark and fuel, did get it briefly started, ran really rough (but with out the second cylinder I know why lol)

Thanks in advance.

 

[jerryjerry05]

Re: 125HP 1987 Force - No Compression

When you pulled the head was there ANY scoring on the cylinder walls???
If so then the hole needs to be rebored and a new piston.$250 for parts and a hole and new gaskets.
You mechanical??
The 90#'s worries me.How was the test done?With a screwin tester?
Plugs out?Throttle open all the way?
How many times did you cycle it?
Fresh water or salt???Salt,be cartefull when removing screws and bolt as the little ones twist off easily.
(It took me about almost 2 hours to remove the 4 screws holding the thermostat cover.Turns out there wasn't one in there???)
Any spray(WD-40)in the cylinders?

 

[tluciffid]

Re: 125HP 1987 Force - No Compression

Slight scoring on the #2 cylinder wall, but not enough to feel the scoring, I can only see it.

Tested with a screw in type compression tester with all plugs in and all plugs out (did two separate tests), but I did not open the throttle.

Used the key to turn over the motor (about 3 seconds per cylinder) not sure how many cycles that is, would guess between 8 and 10 though. Does it make a difference with the throttle open / closed when you do a compression test? If so, I can go back and test it again with the throttle open.

Fresh water, bolts came out fairly easy.

I didn't use any spray in the cylinders, didn't want to ruin my new head gasket I did put some oil in the cylinder before I set the head gasket.


From what I can tell I wouldn't think that the tiny bit of scoring on that cylinder wall would make it lose ALL compression, but I am not extremely mechanical, I'm good enough to follow directions (replaced the head gasket in my ex wife's car by the book) as for machining / boring the cylinder, I would have to take that to someone so I don't screw it up.

 

[tluciffid]

Re: 125HP 1987 Force - No Compression

Ok, so went back and did another compression test (yes my boat is not at my house at this time)

Results with the throttle all the way open. All plugs removed

1- 103#
2- Sadly still 0#
3- 105#
4- 105#

I know it's not optimal, but it's better than the first tests. Also tightened down the compression gauge all the way this time lol, that's probably why they were so low to begin with.

 

[jerryjerry05]

Re: 125HP 1987 Force - No Compression

The rings must be siezed to the piston.Something you can't see unless you take off the exhaust chest cover or the 4 covers on the ignition side.
The cover on the exhaust side,be real carefull when removing the screws as they will twist off REAL easy.
Throttle open wouldn't make nuch difference.
2-3 second might not be enough to get a good reading on the 90#er's.
But 2-3 seconds would be enough to tell you that there is a problem on the one.
A good guage will read over 120 if the walls/ring are good.
Minor scoring is a sign that something is going bad SOON!

 

[tluciffid]

Re: 125HP 1987 Force - No Compression

Ok, so I started making a list as to what I need, just need to know what else I should replace while I'm digging around in the motor.

So far about all I can tell is the rings (on all 4 pistons) and the complete gasket set.

Should I replace anything else while I'm in there?