Mercruiser 120 I/O-- Cam Chain cover question

klaucke · #1 07-10-2007, 10:59 PM

Hi guys, I've got a leak on my cam chain cover. My engine/outdrive is a 120hp MerCruiser Alpha 1, circa 1985. I was wondering if anyone knew if replacing the cover involves removing the oil pan. The MerCruiser manual I have says to remove to oil pan first, then the cam chain cover, but it looks like you might not need to remove the oil pan. I find sometimes manuals like that assume that if you are removing the cam chain cover, then you will be servicing the cam chain, etc, and hence removing the oil pan would be helpful to work on those deeper parts of the engine-- but perhaps this is unnecessary for just replacing the cam chain cover.

If I do have to remove the oil pan, I'll instead consider patching the pin hole, so I don't have to open a potential can of worms. If the oil pan doesn't need to be removed, I'll just replace the cover w/ a new one. I need to get this done soon, though, so my boat can be usable again.

Thanks in advance.

1bayouboy · #2 07-10-2007, 11:25 PM

Got me on that one....but seems like the cam cover has an overlap on the oil pan. I'm not sure what the gasket arrangement is...

You can check out www.go-fast.com and go to the merc parts link.....look up parts with pictures and they have exploded diagrams.....might help if the diagram is clear and you can see the gasket arrangement.

NAHIM · #3 07-16-2007, 06:20 PM

can you send me pics of you're boat. I love the 20 i/o design

NAHIM · #4 07-16-2007, 06:25 PM

Send me the serial number of the engine and I can help you. You're boat needs a CMD 1.7 120hp Diesel.

oldbluesplayer · #5 07-17-2007, 12:42 PM

Klaucke -

the oil pan butts up to the cam chain cover, with a seal between the two, which can, over time, squeeze out, causing an oil leak. It's a weak design, but easy to build, and in an auto application, the original design, a minor leak is no big deal. The oil inside the cam chain cover is not under pressure, so any leak will not be serious.

To do it right, the oil pan must be dropped. The cam chain cover has a hole in it, with a seal - the crankshaft snout comes out thru that - thus, it critically locates the cam chain cover - what I'm saying is that the cam chain cover has to go straight onto the fron of the block, located by the seal for the crank snout, and then the oil pan can be pulled down onto the cam chain cover, compressing the gasket between the two. You won't be able to do it backwards.

However, because the oil inside the cam chain cover is not under pressure, you might well be able to survive the season by cleaning off the outer surface well, getting rid of all traces of oil, and then slobbering a band aid of good automotive gasket making RTV, over the area. I've done this before on a leaking valve cover gasket, and had good success - though at the end of the season you will want to get it properly taken care of.

hope that helps. Good Luck !!

Bill

klaucke · #6 07-18-2007, 10:09 PM

Bill-- after weighing my options for this problem, I decided to just patch the cover. I found some small pin holes in the upper portion of the cover and covered them w/ some Loctite brand 2-part epoxy, which seems to be pretty tough stuff. I also painted some of the rusty areas on the cam chain cover which were never painted from the factory, namely behind the crank pulley. I then used a crane built off a tree to reinstall: pick up motor, drive boat under.

I didn't feel like going through the pain of removing the oil pan. The seals b/w the oil pan and crankshaft seemed to be OK, in that if they do weep, it's an acceptable amount.

Ultimately, I'd like to put in a 3 liter inline 4 w/ 140hp, and I have another spare motor (w/ a bad head gasket), so I won't worry too much about this one. I'd rather spend my time fishing than working on the motor unnecessarily.

While I was working on the boat, I removed the bow rail as well, b/c it's just a PITA when trying to jump into the boat or haul the anchor in. The lines on the boat are a lot cleaner now too.