1973 Mercruiser 165 inline 6 question

[bobby416n]

I have an older MFG Caprice Classic 21ft cuddy with the inline 6 mercruiser 165. The boat has sat for a couple years without use but has been ran every year with the water muffs on it. Last summer I did not get it in the water also due to health issues but now I'm doing much better. The winter before last the snow was so heavy on my cover that it collapsed down onto the engine cover area. I started the boat last summer with the muffs but didnt run it that long. This summer I rebuilt the carburetor already and it fired right up and ran nice and smooth but noticed a small water leak on back side of the intake/exhaust manifold. I also pulled the dipstick and found a milky residue in the oil. Water is getting in the oil somewhere. I pulled the exhaust manifold to check there an see if I had a crack or bad gasket but gasket looks good but did find a freeze plug that rusted through causing the water leak. Is it possible that the milky oil is because of condensation of the motor sitting without use for few years???

 

There wasn't a drastic change in oil level after running the engine for at least 15 minutes. I did put an engine flush solution in the oil and ran it for 5 minutes then drained the oil. I have new freeze plugs on order and replacing all of them while it is apart.

 

Any marine mechanics out there with any thoughts or advice???

 

Thanks

[L&M]

I would opt for condensation first with what you've said & the engine in question. Drain it well & if you have enough room to drain it out thru the pan all the better. Put a fresh filter & a good grade of straight HD30W oil in it & keep an eye on it.

[bobby416n]

Thanks L&M I was thinking condensation also but wanted to make sure while I had part of the engine torn down. I get the new freeze plugs from NAPA in the morning so i can possibly get it back together after work tomorrow night.

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[bobby416n]

I would opt for condensation first with what you've said & the engine in question. Drain it well & if you have enough room to drain it out thru the pan all the better. Put a fresh filter & a good grade of straight HD30W oil in it & keep an eye on it.

L&M,

Giving you an update on my boat motor findings! It turns out that I did have a bad head gasket. So here is what I done:

Pulled intake manifold and gasket looked good. Found that one small freeze plug that rusted through so I replaced all 3 on the head. I took the head off to check that gasket before putting back together and did find that the port holes between number 5 and 6 cylinders has rust through for water port and oil ports to push rods. It wasn't reel bad yet but it could have gotten worse. I replaced it and torqued down the head in the 3 step process and done a cold valve lash adjustment. It started right up but I had to readjust valve rockers slight afterwards while it was running to get rid of slight ticking. I ran motor for over a half hour now on water muffs and no milky oil and motor runs great. Hoping for final test out on the waters with it this weekend.

[L&M]

Good to hear you found the problems Bob.  By the sounds of it that motor has been replaced at one time or another with an automotive replacement and/or parts. Original M/C would of had brass soft plugs & a stainless marine head gasket eliminating both problems you found. You don't see many of the older straight 6  160 & 165hp motors anymore but they were a great engine in there day & still are for that matter. Good luck with her.  

[Xxx]

I totally agree with ya on the strait six motors, I had one in a 18ft Sea Ray but that was a 140hp, I rebuilt the motor and carb. I used that boat on Erie, Ontario, that was a good motor. The old 6's on the road were indestructible also, the 200, and 250, and the 300's were hard working motors also, they lasted way longer than the early V8's, best of luck to ya!!

Edited July 21, 2016 by pap