1989 Force 85 compression issues

[Thebevis]

I have a 1989 force 85. I have had a lot of issues(carbs mostly). That is another issue Ill deal with later. I was recently out on the lake and as usual the motor was giving me fits. I decided enough was enough. I need to find these issues with this motor. I do have a pretty good understanding about engines so I decided to do a little investigating. So I started out with the basics. Compression, Fuel, Spark. I didn't get past compression. LOL. I did a compression test on the motor(motor was cold. The reading were #1-120psi #2-35-psi #3-118psi. I only used one compression tester but I checked it several times. I was thinking maybe it was a ring issue so I put Deep Creep in the number 2 cylinder and let it set overnight. I started it up the next day and let the engine get warm and did another test. It shot up to a whopping 41psi. After saying a few choice words....... I took the motor off the boat, and started removing the head, hoping for the best but expecting the worst. Hopefully I lucked out.

I will try to post some pics, but my computer is not cooperating right now. I noticed that the head gasket was broke on cylinder 2 and also on 3. Would that cause that big of a compression drop in cylinder 2, or am I looking at a bigger issue. I did an inspection on the cylinders and they all are in really good shape. I can even still see the cross hatching on the cylinder walls. I few thing I did notice is the carbon build up on the top of cylinder 2 is pretty clean compaired to the others. Could that be just because of the broken head gasket, or could it be something else? My other question..... now that I have already torn the head off should I just replace the head gasket and try the compression test again, or should I dig deeper and maybe replace the rings while I am at it? What other damage could have been done to the engine with a broken head gasket, and what should I look for?

This is only the first of a few problems with this motor, but I pretty confident that I can get it running like a champ. Thank you all in advance.

 

[pnwboat]

I would try replacing the head gasket and checking the compression again. The rings themselves don't really wear that much. It's common for carbon build up in the ring grooves that prevent the rings from moving freely to conform to the cylinder walls and seal properly. It's also common for the rings to catch the edge of the exhaust port and break. Sometimes you can see a small piece of the top of the piston missing or what looks like a dent on the outer top edge of the piston which can be a sign that the ring has broken.

You can also remove the by-pass covers and inspect pistons/rings through the intake/by-pass ports in the side of the cylinder. Look for excessive scoring and carbon build up on the piston itself.

 

[Nordin]

Agree with pnwboat. Replace the old headgasket, check the cylinder walls and if you have a broken top ring (common on these engines) you will see scoring.
A new gasket is cheap and you will need it anyway if there are more issues with the block.

A clean pistontop indicate that water is leaking in to the cylinder. You will also see a clean head at number 2 cylinder.

 

[jerryjerry05]

IF??? There is no scoring then the rings are probably ok.
A gasket blowing out on 2 cyl is unusual but there is always something new when it comes to working on motors.

Yes the low comp is due to the size of the hole in the gasket..

Had a miss develop in one of my 85's pulled plugs and saw water on the bottom.
Did a comp test and still had 145 on all 3.

New gasket and it ran great.

 

[Thebevis]

Top of pistons The head gasket on cylinder 2 head gasket on cylinder 2 and 3

 

[Thebevis]

Thanks for the quick response. I think I will take a closer look at cylinder 2 rings through the bypass ports like you said. There is a little bit of scoring on the upper side of cylinder wall 2, but it is not excessive. My fingernail dosent catch on it when I run it over the scoring. If everything looks good I will put a new head gasket on it and try a compression test again. Being kinda new to outboards this is pretty cool learning about all this. Another question, what do you guys recommend to use to clean the head gasket mating surfaces in preparation for a new head gasket? Should I clean all the carbon buildup on the head or just leave it alone? One more question, I have taken the lower end off the motor so I can do a waterpump changeout. Is it ok to do a compression check and turn the motor over with the lower end off?

 

[Frank Acampora]

It is better than OK! You don't need to worry about damaging the impeller. When doing the compression testing, be certain to remove all three plugs and ground them. They must be able to spark otherwise you can get a feedback situation which will damage the CD unit.

Looking at the rings through the bypass ports will usually not tell you much since the damage usually occurs on the exhaust side. Sometimes you can see aluminum rub-off on the bypass side of the piston.

I do not recommend removing the exhaust cover because these bolts tend to corrode and it is possible to snap a few while removing them. Plus, the gaskets are almost always destroyed thus needing replacement. Too much risk for a small possible return.

Put on the new head gasket and check compression. Then, if a problem still appears check the rings. Don't fix what 'aint broke!

 

[Thebevis]

Thanks Frank, jerry, and everyone else. You all have been a tremendous help. I will put a new gasket on, torque it down and run the compression tests and I'll post my results. Like I said this is the first on multiple problems I am having so everyone's knowledge is much appreciated.

 

[jerryjerry05]

IF??? There is scoring then it's only gonna get worse.
How much play with the piston?
Move it side to side and see how it compares to the others.

 

[Jiggz]

Can you post pic of the cylinders #2 and #3. Make sure it is a good pic showing the scoring if any. This is better done with the piston at BDC on each cylinder.

 

[Thebevis]

Ok, Sorry it been a few days. Pretty hectic schedule. I have received all the parts I think I need. Head gasket, plugs, ect. Ill try and post the photos of the 2 and 3 cylinder scoring. I do have a little play in piston number 2 but its pretty comparable to cylinder 1 and 3. Again its my opinion that the little bit of scoring it has is not deep and looks like it will be just fine. I ill let you guys look at the photos and maybe you can give me a better idea. On a side note... this was the first time I dropped the lower end off the motor. Im glad I did. The impeller looked pretty bad. A couple questions for you all. As I pulled the drive shaft off from the motor a rubber piece and a coller dropped off of it. I am not quite sure how that went back together on the drive shaft. Ill send a photo. Another question, Do you recommend I put a tell tail on it? It has the plug right above the thermostat. Or should I put a water temp guage there. Or should I just let it be? I do have more questions but I don't want to overwhelm myself. Thanks again.

 

[Jiggz]

No Title

This is how the rubber and collar goes back on the shaft. The steel collar flat side is facing down while the raise part is where the rubber boot seats.

 

[Jiggz]

The fact the impeller was in a very bad shape there is a good possibility the engine could have overheated hence causing a damage to the rings. Now that you've let us know about this, it is highly recommended you test the hi temp alarm buzzer make sure it works and probably broken rings on #2. Again a good pic of the cylinders will let us know.