another head gasket question (new pics)

[CapCramer]

I noticed that on my 3cyl single carb 70hp Force, that my #2 plug was clean as a whistle and had what looked like a fine layer of moisture on the flat surface of the plug. I just touched it and it dissappeared where I touched it, and when I layed it on the bench, I looked later and it was gone (evaporated?) The other 2 cyl were very oily, wet black shiny surface areas. This motor does run somewhat rough at low speed but fine at mid-high. Is it possible I am getting some water introduced into this center cylinder? Cylinders had 120-120-115psi. Head has never been off judging by the painted bolts. Any thoughts?

 

[jerryjerry05]

Re: another head gasket question

Re: another head gasket question

You can still have water coming into the cylinder and have good comp.I had an 85 that was doing that.Comp 150# all 3cyl and the#3 cylinder was getting wet.I found a bad head gasket.A small spot had formed on the head.
It's possible water is coming thru the head or someplace else.
Get a new head gasket and replace. Check the old for water or hot spots. Make sure there are no bad spots on the head.Good luck,J

 

[john from md]

Re: another head gasket question

Re: another head gasket question

+1 c;ean plug and rough engine = water in cylinder. Fix fast.

John

 

[CapCramer]

Re: another head gasket question

Re: another head gasket question

You guys are the best. of to my only local merc dealer. She shakes her head when she sees me coming...now I have the part #'s with me. If she wasn't so cute I would go outta town. Looks like all I need this time is a head gasket, don't see anything else that I might disturb. Thermostat was just done. Thanks again guys!

 

[jasonbailey]

Re: another head gasket question

Re: another head gasket question

When I did my head gasket for the 2nd time I also replaced all of the head bolts with new bolts. I did not do that the first time and ended up buying another head gasket. Just a suggestion, the other more experienced guys can weigh in on that.

 

[CapCramer]

Re: another head gasket question

Re: another head gasket question

Alright, I took it off. I am typing this because I only want to see certain things cause its gonna go back together to hopefully make the season. Here goes: First pic shows head as was taken off. Notice how nice the water infiltration cleaned her up?

Now take a look at the bottom of the fire ring in the head gasket. See the hit it took?
Nice little pop, just enough to deform the fire ring to allow the water in.

What caused this deformed fire ring? Those in the know already guessed by looking at the first pic. They see how many times the piston ring was smashed by the piston top. See what it did to the cylinder wall?

Here's where it came out from under the piston. No sign of it anywhere. Who knows when this happened. Before I got it. Being that it runs nice, I am going to put it together and run it. I know the pieces are in there somewhere but hopefully they are outta the way. We are never more than 1000ft from the populated shoreline.

Any thoughts before I put it together? I did clean up the rough edge on the piston and
a nick on the alum head. Torque values are not listed in my Seloc. 70hp Ser#OEO10843
Thanks!

 

[Frank Acampora]

Re: another head gasket question (new pics)

#2 piston and combustion chamber show moderate detonation damage! You caught it just in time. That was not a result of water entering the cylinder. It was the result of lean running. Remove the carb, clean it! Be certain the low speed needle is set rich enough. Put a fuel filter between the fuel pump and carbs.

Matter of fact, clean all the carbs and re-synch the engine carbs and timing. Be certain all the carbs are set rich enough to prevent further detonation--no leaner than 3/4 turns out from lightly seated, no matter how she idles. Timing set to 30 degrees before top dead center at full throttle. Get rid of the Seloc and buy either a factory manual (preferred) or a Clymers (2nd best)

It shopuld accelerate smoothly from a full stop at full throttle. (hole shot) If it sags and possibly slows then picks-up and accelerates, it is too lean. Richen all three needles 1/8 turn at a time until it accelerates properly.

 

[CapCramer]

Re: another head gasket question (new pics)

Hi Frank, thanks for the reply. My question is I have the 3cyl with the single carb. #1 and #3 cylinders are both oil fouling the plugs, but #2 is what seems to me being washed clean.
Can the single carb just lean out that #2 cyl only? I did have what looked like moisture on the #2 plug when I pulled it and it evaporated clean on the workbench. And I did find a nick/hit in the fire ring which would possibly allow water to enter. When I go together I guess a test run will tell. Thoughts?

 

[Frank Acampora]

Re: another head gasket question (new pics)

OOPS! Yeah! I'm used to working on 3 carb engines. HOWEVER: If you look closely, you will see that Merc. used a system of baffles in the manifold to try to ensure even distribution of the intake fuel/air mix. Note that the carb is not centered between all three cylinders but biased a bit toward the top. Note that the carb opening in the manifold is not a full circle. Merc. took a good three carb system and crapped it up to save money on carbs. And, they changed the block front end so you can not retro-fit to a three carb system.

I suspect that due to the larger crankcase volume (the crank cheeks on #2 are smaller) and the baffle design, that the center cylinder runs a bit leaner than the other two. If the carb is set just a tad too lean, the center will preferentially detonate while the others do not notice it.

The other two cylinders don't appear to be really rich. It is normal to have some deposits on the piston heads.

If detonation damages the head gasket, you will, of course get some water infiltration, but it is after the fact, not the cause. There is no doubt that the damage you see in #2 is lean run detonation. Left to continue, it will melt the exhaust side of the piston and shatter the rings resulting in the need for a complete rebuild.

Again. Clean and re-set the carb. I believe that Merc installed a fuel filter so either clean it or replace it as a preventive maintenance item.

 

[CapCramer]

Re: another head gasket question (new pics)

Your credentials are impeccable so I will follow your instruction. Thanks for all the help you give people in here along with the many other knowledgeable people. I thank you all.

 

[GrindKore]

Re: another head gasket question (new pics)

Last year I have had to replace pistons and hone the cylinders, somewhat similar scenario. Take a look here http://forums.iboats.com/showthread.php?t=266436