Low compression #2 Cylinder 89 85HP 856X9C

[ForceEightyFive]

My motor ran great all day Sunday on WOT, but as I was pulling it up to the dock to trailer it it cut out on me. Once I got it on the trailer after a few attempts since it kept cutting on me, I pulled the cowl off and noticed the thermostat cover paint appeared to have discolored from heat. Also the thermostat gasket sealant appears to have ran down the head gasket cover. Today, after work I did a compression test on my three cylinder engine and found I had low compression on the #2 cylinder (35PSI). The other two came in at 120PSI. Good spark on all three. Thermostat tested fine. I put in some oil into the #2 and got the same low reading. From my reading this indicates that it is not the rings but most likely the head gasket. Also, if I had holed the piston I would have zero compression, right? Any comment would be appreciated on what I should do. Thanks you.

 

[foodfisher]

Re: Low compression #2 Cylinder 89 85HP 856X9C

Consistant low compression reading=pull the head and looksee.

 

[pnwboat]

Re: Low compression #2 Cylinder 89 85HP 856X9C

Yep.... hole in piston usually equals zero pounds of compression. Hopefully just a head gasket. Also make sure #2 carburetor is is not gummed up causing a lean mixture to #2 cylinder. Install an inline fuel filter between the fuel pump and carburetors if you don't already have one. Double check the fuel pump diaphragm too.

 

[jerryjerry05]

Re: Low compression #2 Cylinder 89 85HP 856X9C

Flashlight, move piston till it's at it farthest. Then look at the piston crown.
Your gonna have to remove the head anyway to check the damage.
Like pnw said,your gonna have to figure out why it's gone bad.
Carb,fuel pump,air screw,overheat(test buzzer),fuel recirc system?
Profile? Location? You might be close to someone who can help?

 

[ForceEightyFive]

Re: Low compression #2 Cylinder 89 85HP 856X9C

Thanks for the responses. Well, I pulled the head today. This is what I found on #2.

 

[foodfisher]

Re: Low compression #2 Cylinder 89 85HP 856X9C

Ouch.

 

[Frank Acampora]

Re: Low compression #2 Cylinder 89 85HP 856X9C

Broken top ring requiring replacing the piston. The bore does not look scored so you can probably get away with a light hone and replacing with a stock size piston and rings (3.3125 bore). It is not a difficult job and does not require disassembling of the engine. You remove the carbs and manifold and access the big end of the connecting rod through the front opening. Look up other posts. There are several. It has been done before.

It should take one day of a weekend.

 

[tater76]

Re: Low compression #2 Cylinder 89 85HP 856X9C

Replace the water pump impeller while your at it. Sounds like you overheated along with the broken ring. Its about $20 bucks to your door, and good, cheap insurance.
@Frank... do you think the broken ring on this could be from a lean running condition? overheat? or just varnished/stuck in place?

 

[Frank Acampora]

Re: Low compression #2 Cylinder 89 85HP 856X9C

In 1989 I believe they all had the semi-keystone top ring. These rings broke for no rhyme or reason. Some ran forever, some broke--you never got a warning and never knew when it might happen. My 150 also has these rings. (It broke two, that's why I got the engine for 300 bucks) I had a couple of stock pistons hanging around that I stuffed into two holes that did break rings. If it should ever happen again I am going to buy 5 Wiseco pistons and stuff them into the engine.

 

[jasonbailey]

Re: Low compression #2 Cylinder 89 85HP 856X9C

Looks like a good project...

If you do decide to replace the piston, you may want to take the head to a machine shop and have it planed back flat. I had a Chrysler 75 HP, it overheated once, blown head gasket. I replaced the gasket without having it planed and it continued to overheat. Took it in had it planed, and all was good. Your overheat condition may have warped the head. Getting it checked by a machine shop is pretty cheap.

I'm not sure of the 85HP design, but my 75 had an outer cover on the head, I also took that off and cleaned some stuff out of there. After all that, all was good. My Chrysler's headbolts torque setting were 220 inch pounds. Get new headbolts as well.

 

[ForceEightyFive]

Re: Low compression #2 Cylinder 89 85HP 856X9C

Im by no means an outboard mechanic but from my reading it looks like it changing out the piston is within my mechanical skills.Ill change out the impellor as well. Ill see about planing the head. The head gasket itself looks fine. I read that its best to reuse if possible instead on putting in a new one. http://forums.iboats.com/force-chrysler-outboards/replacing-piston-3-4-cylinder-engines-289147.html No scoring on any of the cylinders. Hopefully the rollers don't go flying all over the place when I detach the rod. Btw will running the outboard on two cylinders cause an overheat? Thanks.

 

[jerryjerry05]

Re: Low compression #2 Cylinder 89 85HP 856X9C

One important thing.
When reassembling, use bearing assembly grease.
It will hold the bearings in place and dissolve quick in the gas/oil as it runs.
Using regular grease can actually burn the bearings and you'll be rebuilding the whole thing.

 

[Frank Acampora]

Re: Low compression #2 Cylinder 89 85HP 856X9C

Don't run it on two cylinders. It will not cause it to overheat, but it will further damage the piston and cylinder. There is still a piece or pieces of broken ring in the piston.

If the head gasket is in good shape and does seal compression, it is acceptable to use it. A new gasket is always better and always recommended by repair manuals, but re-using the old one does have the positive that it is not necessary to re-torque the head bolts after running the engine for the first time.

 

[ForceEightyFive]

Re: Low compression #2 Cylinder 89 85HP 856X9C

Quick question. What does the "1" stamped on each piston mean? I think it means standard size but just want to make sure before I start ordering parts. Thanks.


Scratch that. Just read that its just the manufacturer's casting mark. Thanks.

http://forums.iboats.com/force-chrysler-outboards/replace-piston-force-1251x9d-592642.html

 

[jerryjerry05]

Re: Low compression #2 Cylinder 89 85HP 856X9C

http://www.powerheadkit.com/images/in progress-2.jpg

 

[ForceEightyFive]

Re: Low compression #2 Cylinder 89 85HP 856X9C

Having a heck of a time getting the rod with the replacement piston back onto the crankshaft. Any tips to get it back on? Thanks.

 

[tater76]

Re: Low compression #2 Cylinder 89 85HP 856X9C

I use a bunch of white lithium grease on the rod end to hold the cage and bearings in place on it. Insert it carefully, and most of the time it goes right in, just go slow. When you get it in place, then you can grease up the other half of the bearing cage, insert bearings, and carefully maneuver it in place. It takes ALOT of patience. Go slow, and walk away when you get frustrated, trust me

I am sure Frank and Jerry do it a little different, maybe they will chime in too.