79 inline 140 milky 5 and 6 plugs

[r j d 76]

Hey there, looking for some help and I'm new to this site.

I picked up a 79 140hp inline, compression is 120-125 across all cylinders, would that be considered good for this motor?
I Cleaned the carbs and got her running. It seems to idle good. Unfortunately after pulling the plugs I found milky film on plugs 5 and 6. Also, plug 3 didn't seam to have oil/gas on it...hmm but #4 did

I have spent the last hour reading some great stuff on the problem(s) on this site so I just wanted to get an opinion if it is the side plate/waterjacket seals or the lower crank seal for the cyl 5 & 6. How long should the job take. I'm okay with doing the work myself but where do I get parts? My local Mercury dealer doesn't seem to want to support these motors anymore.
For the cyl. 3 problem could it have a bad read?


Thank you for your help in advance.

 

[Chris1956]

Re: 79 inline 140 milky 5 and 6 plugs

It is likely the lower crank seals causing the water infiltration into #5 and #6. It is not a bad repair, but it does take some effort. Here is the basic outline:

Disconnect electrical, spark plugs, drop gearcase, remove cowling support, ign wiring and starter. Remove lowest cowling 94 SS self tapping screws, and cowling. Disconnect powerhead mounting bolts, including the two nuts hiding above the steering arm and below the exhaust extension. Raise powerhead with a suitable hoist. I use a crummy block and tackle. Lay block on bench, plug holes down. Loosen lowest 3 or 4 crankcase bolts. Remove end cap bolts (3 or 4 of them). Pull end cap off crankshaft. Replace seals, using 3 seals if you can squeeze them in.

Probably #3 reed block is OK. A simple test is to turn the flywheel to lower #3 piston and see if you feel air coming out of middle carb. if not, reeds are good, which is very likely.