MCM 165 leak down and comp. test results

[natemoore]

MCM 165, 1987 engine

witnessing white smoke (or steam) upon warm engine restart

losing coolant somewhere

getting whiffs of coolant here and there

suspect that coolant is being burned up inside cylinders

otherwise engine runs okay

Leak down test results:

test 1 test 2
cyl 1: 35% 38%
cyl 2: 40% 41%
cyl 3: 43% 54%
cyl 4: 34% 40%

I heard air coming from valve cover, carb, and exhaust on all these. None were very loud.

Dry/wet compression test results:

Dry Wet
cyl 1: 180 180
cyl 2: 162 177
cyl 3: 155 162
cyl 4: 142 165

Keep in mind that I had a hard time getting a good seal on cyl 4 because of corrosion, so 4 may be better than what it shows.

What do you guys think? Can I continue to use this boat until a winter rebuild or do I need to pull the engine and rebuild it now. My wife is a teacher and is off until mid-August, so she'd rather me wait if I can.

 

[Don S]

Re: MCM 165 leak down and comp. test results

My wife is a teacher and is off until mid-August, so she'd rather me wait if I can.

When mechanical things go bad, the need fixed. If not fixed, the WILL get worse, and more expensive to fix.
You have a problem, and you know it. YOU get to make the decision to run it or not. Personally, my crystal ball is broken.

 

[natemoore]

Re: MCM 165 leak down and comp. test results

When mechanical things go bad, the need fixed. If not fixed, the WILL get worse, and more expensive to fix.
You have a problem, and you know it. YOU get to make the decision to run it or not. Personally, my crystal ball is broken.

Thank you sir! May I have another?

Is there anyone else up there we can talk to?

 

[stonyloam]

Re: MCM 165 leak down and comp. test results

Just went through that! I would not wait, you probably have coolant leaking into #4 cylinder. It is probably eroding your valve seats and will only get worse. Don is right waiting is only asking for bigger trouble. With those numbers it probably does not need a "rebuild", just head work. Pull the head asap and get a valve job done. Replace the head gasket with a genuine OEM Mercruisre head gasket. Have your machinist make sure that the valve height remains the same so you don't have to replace the pushrods. Pulling the head is not too bad on that engine. Good luck.

 

[natemoore]

Re: MCM 165 leak down and comp. test results

Just went through that! I would not wait, you probably have coolant leaking into #4 cylinder. It is probably eroding your valve seats and will only get worse. Don is right waiting is only asking for bigger trouble. With those numbers it probably does not need a "rebuild", just head work. Pull the head asap and get a valve job done. Replace the head gasket with a genuine OEM Mercruisre head gasket. Have your machinist make sure that the valve height remains the same so you don't have to replace the pushrods. Pulling the head is not too bad on that engine. Good luck.

I appreciate all the good information. I'll start on her tomorrow.

 

[natemoore]

Re: MCM 165 leak down and comp. test results

....genuine OEM Mercruisre head gasket. Have your machinist make sure that the valve height remains the same so you don't have to replace the pushrods. Pulling the head is not too bad on that engine. Good luck.

I haven't been able to locate any online sources for OEM Mercruiser, just Sierra on this website and another called Quicksilver. Does Mercury Marine Corporation still offer them? What about this thicker gasket 27-94954A1?

Nate

 

[45Auto]

Re: MCM 165 leak down and comp. test results

Quicksilver IS Mercruiser's name for their parts. Quicksilver is OEM.

 

[stonyloam]

Re: MCM 165 leak down and comp. test results

Try http://www.mercruiserparts.com/ part# 27-13709 or your local dealer should be able to get you one. I don't know about the thicker gasket.

 

[natemoore]

Re: MCM 165 leak down and comp. test results

Try http://www.mercruiserparts.com/ part# 27-13709 or your local dealer should be able to get you one. I don't know about the thicker gasket.

Thanks. I spent the day looking for online sources. I've been able to find head bolts and gaskets, plus plenty of valve train parts.

Those long bolts are expensive! $15 each. Any alternatives to this?

 

[stonyloam]

Re: MCM 165 leak down and comp. test results

Thanks. I spent the day looking for online sources. I've been able to find head bolts and gaskets, plus plenty of valve train parts.

Those long bolts are expensive! $15 each. Any alternatives to this?

You should not need to replace the bolts. The Mercruiser manual says "clean all bolts and bolt holes" and to coat bolt threads and underside of bolt head with perfect seal, nothing about replacing them with new ones. If your bolts are in good shape you should be able to clean and reuse them. I cleaned the old sealant out of the threads on mine and they appeared to be just fine. I reused all of my valvetrain parts. If you replace valvetrain parts you have to check the valve clearance to make sure that your pushrods are the correct length since there is no adjustment on the rockers. PITA!

 

[cr2k]

Re: MCM 165 leak down and comp. test results

If yo don't have one get a thread tap for your block holes to chase out the head bolt holes. Then blow them out with air to get all the crap out. Makes torquing them more accurate. While you have the head off use a good straight edge to see if your block surface is flat. If not you might consider the thicker head gasket to make up for it.

 

[natemoore]

Re: MCM 165 leak down and comp. test results

You should not need to replace the bolts. The Mercruiser manual says "clean all bolts and bolt holes" and to coat bolt threads and underside of bolt head with perfect seal, nothing about replacing them with new ones. If your bolts are in good shape you should be able to clean and reuse them. I cleaned the old sealant out of the threads on mine and they appeared to be just fine. I reused all of my valvetrain parts. If you replace valvetrain parts you have to check the valve clearance to make sure that your pushrods are the correct length since there is no adjustment on the rockers. PITA!

The bolt heads are a little corroded and I'm worried about being able to torque them down to 130 ft-lbs without rounding off the corners. I'm going to add a gutter inside the doghouse to keep the water off the engine.