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Oil leak New Boater as well as a new Mechanic

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skip_evans

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"Hey everyone.

I have a 3

"Hey everyone.

I have a 3.8l Mercruiser with a Alpha 1. I just started the engine today after installing it. It is a new longblock.

There is a pretty hefty leak coming from the area where the starter bolts up to the block. I removed the starter and tightened the oil pan bolt on the back corner of the oil pan. That didn't help.

I'm not even sure that the leak is there. It is very hard to see where the leak is originating. I'm using a light and mirror too.

My plan is to remove the oil pan and put a new gasket on. Should this be my next step? I was very careful about installing this gasket. I'm just not sure that it is leaking from there. I'm worried that it may be leaking from a seal on the end of the crankshaft. I'm not sure if I used the correct terminology there. I'm not sure if there is a seal there. I just hope that this is a leak that I'm capable of repairing.

Thanks, Skip"
 
"Skip
Before you go and repla

"Skip
Before you go and replace your oil pan (sump) gasket I would be doing everything I could to confirm that as the problem.
Degrease the engine in the area of the oil leak, let the engine dry and then run it on the flushing muffs while you use your mirror and the brightest light you have.
There is a rear main oil seal on your engine and that is also a place for a possible leak.
If you are loosing a large amount of oil you should be able to get a good idea where it is coming from before you start surgery.
Cheers
Peter C"
 
"Ayuh,....... I completely Agr

"Ayuh,....... I completely Agree with Peter,......

But,......
I never knew Mercruiser Ever used the 3.8l motors..........."
 
"What do you mean by "new

"What do you mean by "new longblock"? Just different or actually new/never installed or used, with fresh paint?"
 
"Thanks Peter,Bondo,and Jim fo

"Thanks Peter,Bondo,and Jim for replying. Peter and Bondo, I'm going to check it out again next Saturday. Also Bondo, the old block had a Mercruiser emblem on it. The flame arrestor says Mercruiser. I really don't know though. I'm new at this.

Jim, it is a rebuilt Marine longblock. I posted on here months ago about buying a boat with a cracked block. I didn't know any better back then. I have learned quite a bit since. A person named Guy on this site has helped me immensely.

I put new manifolds, risers, water pump, all new bellows, shift cable etc.

I was very careful doing everything including all of the gaskets. That is why I suspect the rear main seal.

I sprayed starting fluid in the carb. and the engine fired up on the first try.

The engine sounds great. This oil leak may do me in though.

Thanks, Skip"
 
"So we know what we are workin

"So we know what we are working on... 3.8L?? (hmmm could it be a Ford, or GM V6??) or could it be the 3.7L inline 4?

If the back of the flywheel is dry, it's not likely rear main. Does sound like a rear main though."
 
"I'm also not sure of this

"I'm also not sure of this engine model, but I will share my experience with my 8.1L Mercruiser inboard. I had a slight oil leak that was very hard to pinpoint. It turned out to be a cracked brass elbow that was used to house the oil pressure sender on. I was 1st told by the Marina Mercruiser mechanics that it was the rear main seal. After lots of properly place paper towels and some real hounding I was able to trace it to the brass elbow. I picked one up at NAPA for less than a buck. The point is, look all over because it will not always be the worst or most expensive part.

Good luck - Mike"
 
"mike - good find! Love those

"mike - good find! Love those types of diagnoses.

If I'm not mistaken, the oil pressure sender is on the back of the block next to the distributor and could be leaking down the back of the bell housing. Intake valley seal could also be the culprit.

Let me know if the back of the flywheel is wet."
 
"Hey Mike,

I will take th

"Hey Mike,

I will take the slow approach to finding the leak. I appreciate the input.

I will post my findings on Sunday.

Thanks to everyone for their help.

Skip"
 
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