85 hp Force **UPDATE** Head gasket?? PICS Added

[jbwillis76]

Hello all,

I got this motor going earlier this spring with y'alls help and now I need it again. 1986 US Marine / Force

Motor has ran great all summer. 5500rpm and running perfect. Last week I was pulling the tube, parked it and when I got back to it (hour) it was hard to crank and to keep running. I lost 1500-2000rpm WOT and it won't idle. Figured I lost a cylinder and I guess I was right.

Just got around to tinkering with it and sure enough the bottom cylinder (no.3) plug is spotless. Here's what I've figured out so far:

Plug has GREAT spark, same as the other two cylinders.
Compression is 135, same as the other two cylinders.
The plug was wet so I'm assuming it is getting fuel. Took the carb off and cleaned it just in case. It was clean and did not change anything.

I'm out of ideas. Air, fuel and spark and it should run. With the motor idling (best it can on two cylinders) pulling the bottom plug wire doesn't change anything so it is definitely not firing on that cylinder. It is also smoking white smoke VERY heavily right now, maybe because it isn't running right, IDK, but it isn't normal.

ANY HELP!

Thanks as usual. James

 

[jbwillis76]

Re: 85 hp Force has me stumped

Re: 85 hp Force has me stumped

**UPDATE**

OK, so I changed electrical components (had spares), nothing changed.

I tested spark with a spark tester that makes the spark jump about a 3/8" gap. Plugs are all hot and firing.

Compression is great, 135 across the board.

So I did some reading and decided I'm getting water in that cylinder to make the plug so spotless (steam cleaned).

I just pulled the head and here is what I found. No.3 cylinder is on top in the pic. Spotless in the "dome".

I saw nothing on the head gasket that stood out to me.

The pistons and cylinders look good. Has some deposits on them but nothing bad. The cylinders still show the honing marks and are smooth with no wear.

Picture of the No. 3 cylinder/piston.

Do you think it is just as simple as being a head gasket (Have a new one ordered and on its way)? Would this cause the trouble I'm having? Is there anything else I should be looking for while I have the head off?

Thanks for the help, James

 

[john from md]

Re: 85 hp Force **UPDATE** Head gasket?? PICS Added

You could have had a water leak when the engine was hot. It isn't unheard of and does clean the head pretty clean. I'm bet'n that the head gasket will cure the problem.

John

 

[jbwillis76]

Re: 85 hp Force **UPDATE** Head gasket?? PICS Added

Yeah John, I hope it fixes it. Just got my head back from the local machine shop to have it surfaced. Didn't feel there was any reason to put it back on without doing it. They told me it was slightly warped which is where it was probably leaking from I'm guessing. From looking at the plugs I took out when I got this boat the bottom plug looks "cleaner" than the rest. I bet it's been leaking for a while but finally got bad when it was hot and I was working the boat pulling tubers.

I'll be sure to let everyone know if that fixed it, for future searches.

James

 

[Frank Acampora]

Re: 85 hp Force **UPDATE** Head gasket?? PICS Added

The other gasket you need to check is the exhaust cover gasket. Down by the dogleg at the #3 cylinder it is thin and can perforate. If it does this, it can or will squirt water into the exhaust ports. There is one gasket on either side of the stainless plate. These two gaskets usually cost about 11 bucks each.

Be careful with the exhaust cover bolts. They are only 1/4 X 20 and tend to corrode in tight. They will snap off if you get ham-handed with them.

 

[jbwillis76]

Re: 85 hp Force **UPDATE** Head gasket?? PICS Added

OK Frank, I'm cussin' you right now .....I only broke 6 of the bolts off......

I guess I'll be drilling those out today.

I am glad you mentioned this though, I would have never thought of it. It does look like it may have been leaking a little down low on one of the gaskets. Ordered some new ones. Thanks again, James