1986 115 inline 6 Help me read my plugs

[redjmp]

I put this motor together about 2 years ago and it runs great!
I pulled the plugs and had a look and they seem a little odd.
Now they have been sitting in that engine since I ran it last in Sept last year. And I did not winterize either.
Seems to me that the top 2 show more dark oil than the others.
The middle 2 seems brownish and show some signs of water and a thim film of rust of rust.
The bottom 2 were very clean which makes me nervous as well. Maybe they are running too lean?
Any ideas whats going on here?

Thanks!
Plugs are #1 on the left and #6 on the right.

 

[Chris1956]

Re: 1986 115 inline 6 Help me read my plugs

OK, Plugs 1-4 look fine. Plug 5 and 6 show some water intrusion. The water intrusion may be from bad crankshaft seals in the lower end cap, or because of the exhaust cover or exhaust baffle is holed or the gaskets are leaking. The exhaust cover and baffle are a real PIA to remove beacuse the bolts corrode up and break when you try to remove them. If you have the patience, pull the powerhead, loosen the crankcase bolts around the lower end cap, remove the end cap and replace the crank seals. Install three seals if you can fit them in. Also install a new end cap oring.

Reassemble and switch the plugs around and retry it. If you still have water intrusion, you need to remove the exhaust cover and inspect the inner exhaust cover and baffle for leakage.

 

[deerhuntre]

Re: 1986 115 inline 6 Help me read my plugs

Are there any tricks of the trade or suggestions for removing the exhaust baffle/cover?

 

[Chris1956]

Re: 1986 115 inline 6 Help me read my plugs

There are several methods to remove the exhaust cover bolts, which minimize breakage. Use some heat to break them loose, use some penetrating oil to break them loose and use an impact driver to break them loose. I would heat up the bolt head with a torch, remove the heat and spray them with PB Blaster. As they cool they would sometimes pull the oil in. Now use a hand impact driver and see if you can break them loose. Repeat as necessary. Be prepared to break a few bolts, however.

After the covers is off, you may be able to turn some of the broken bolts out with a vicegrip. Other may need to be drilled and retapped.

 

[redjmp]

Re: 1986 115 inline 6 Help me read my plugs

So you figure that water is getting to #5 & 6?
But they don't show any signs of water or rust.
Those plugs are just cleaner than the rest and now I'm thinking that its because I have an .074 jet in the bottom carb while the top 2 have .076's.
I put 1 size smaller in that carb because the bottom 2 plugs would always get fouled especially at idle.
I thought it was because of the extra effects of gravity on the fuel line for the lower carb.
But that I later attributed to a leaking cover which I fixed by using just rtv and no gasket.
Seems water would drip onto those plugs and make them run much too cool.
Now they are running dry and I think a little too lean?
What plug looks better do you folks think? # 1 or #6 ?

Now it is the middle 2 plugs , # 3 & 4, that have the water and rust.
What about those?
Exhaust cover or something else?
Do you still think the bottoms seals need attention?

The exhaust cover was the only thing I did not touch for fear of snapping those bolts.


Anyways Chris, did you think the bottom plugs were too clean and thats what made you suspect water intrusion?

Thanks a million for all the help!

 

[Chris1956]

Re: 1986 115 inline 6 Help me read my plugs

Yes, normally when you see the bottom plugs that clean, you suspect that they are getting steam cleaned by some water intrusion. Since it is the bottom plugs, it just might be the crank seals, in the lower endcap. You might try to replace those first and see if it gets better.

Are you dropping the #6 cylinder at speed?

 

[redjmp]

Re: 1986 115 inline 6 Help me read my plugs

Well I did indeed have a .074 jet in the bottom carb so that probably explains why the plugs were so clean.
I will try to find the .076 jet and see if that helps.
But 3 and 4 have me worried. Is there anything thing other than the exhaust cover that could cause water to get in those 2 holes ?
Will I ruin it if I keep running it with the water intrusion?
I don't think it drops any cylinders at any speed.
I had it going 51mph on gps turning a cupped SS 19p @ 5750 with a full load of gear and people.

 

[chris.olson]

Re: 1986 115 inline 6 Help me read my plugs

Is there anything thing other than the exhaust cover that could cause water to get in those 2 holes ?

Will I ruin it if I keep running it with the water intrusion?​

Only if you have a hole in a cylinder, which is unlikely. Leaking and/or blown exhaust cover/baffle gaskets are not uncommon. There's a 99% probability that if you have water intrusion in a cylinder, and it's not the bottom hole, it's the baffle/cover gaskets.

As the other Chris noted, they can be a PITA to replace because you'll probably break some bolts off. It's easiest to do the job with the powerhead off on the bench, which makes drilling the broken bolts much easier. When reassembling I use stainless hardware and anti-sieze compound on the threads and bolt shanks. If your engine doesn't have stainless hardware in it you can get 5/16" stainless bolts for that cover and baffle thru Fastenal for a portion of what Mercury Marine wants for them.​

You WILL damage a cylinder if you have water intrusion. You'll end up scoring the bore and/or piston, or stick the rings. The same corrosion you see on the spark plugs will happen in the bore. They're designed to be lubricated by oil, not water. And water displaces your lubricating oil.
--
Chris​