1 Attachment(s)
water intrusion 1979 Merc 115
I am getting water intrusion in number 2 cylinder. Where would it be coming from?
Here is a little info. I purchased a 1979 1/2 Merc 115 outboard for my project boat. She ran really good. never took her over 5500 rpm and always pissing strong, but I didn't have a temp gauge working at the time, normally playing around 4 to 5 thousand rpms.
I got a a deal on a 22 pitch SS prop on market place and got 50mph out of her at 5k rpms on Saturday. I tried to raise the motor up another half an inch and noticed it was not pissing as strong so I lowered it back down and quit trying to go faster at that time. Sunday I put the 15 pitch prop on it, lowered the motor way down, and went to the lake to play with some family and friends pulling a small tube. Temp sending unit installed and never got hot on Sunday..
I did have a hard time starting her at the dock and a fellow boater gave me a shot of ether and she fired up and seemed to run good. Took a warm up lap nice and easy around the lake, beached the boat and met up with my friends. we discussed getting the small tube and letting the kids play on a tube for a while so I let the graduate drive the boat back to the dock. her first time driving any boat. she did great. No issues, started right up, ran pretty good, but idle in gear was a little bit rough. I was thinking it maybe needed a little carb tuning, no biggy.
Got the tubes and started to play. The motor started to run a little rougher at idle, seemed to be smoking a bit more and running a bit rough. smelled like maybe a little rich. stalled a few times in gear at idle, but ran and pulled the tube with no issues after I put it in neutral and revved her up a little bit, seemed to clean it out and ran better.
I just wanted to give some back story to my issue so to my point now. Monday I pulled the boat out of the garage and figured I would see if I can get her to idle better adjusting the carbs a little bit. While I was filling up the 55gal barrel with water, I figured I would pull, check, and clean the plugs. number 2 plug had a milky sludge on it. I believe I understand these motors dont have heads or head gaskets.
I did sit down and try to do some research on my own and was surprised to find there is not really a head or head gasket on these motors to fail if I am looking at this right. I thought for sure that the cover was the head. I have worked on many small engines, but very little on Mercs. mostly air cooled, lawn mower, dirt bikes, or ATVs. Hoping there is just a failure on the exhaust side gaskets allowing water in on the downstroke from this side. Previous owner claims these gaskets were just replaced by a mechanic. It does look like new gaskets from the outside. I did notice one of the lower bolts loose a week ago and weeping a bit of water, so I tightened that one bolt and didnt think of it again till now.
I went back out and finished cleaning all the plugs and did a compression test. Numbers below. Put her back together and fired her up in a 55 gal barrel of water to do a little tuning on the air mixture screws on the carbs. Got her to smooth out and idle a bit better. I didnt take a pic of the plug the first time I pulled it but here is a picture of number 2 after running for about 10 to 15 minutes. I dont like the looks of this, and fearing the worst, but keeping my fingers crossed.
Attachment 520380
Compression numbers.
1-115
2-120
3,4,5-125
6-120
What is the bad news here?
Did I hurt this motor some time?
Where do I look for damage?
Planning on maybe pulling the exhaust side apart today, but will first just check for loose bolts on this side. If I find loose bolts I may just snug them all up on this side, pray, and run again in the bucket of water. I hope to hear from some people with lots of experience with these old inline Mercs and can give some insight.
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