Looks like rear main. Put it in Friday, Did cam break in, motor break in, changed oil, everything OK. Did a run to Kellys sunday and had a bilge full of oil. Looks to be coming out of the flywheel cover. The only thing I thought was strange was the oil pressure was really high, over 80 psi. Could that have caused the seal failure? Its only 60 now. Any ideas? Im pulling the boat today and starting on the engine tomorow. Should I put the stock pump back in? I have a Melings HV in it now.

Tom,
I'm sorry to hear about your leak. Did you do your cam break in, in or out of the boat? If I recall you used that Federal Mogul cam that some of the other guys are using. Did the engine with the new heads make good power with that combo? Also, I would not change the oil pump. If it is Mark IV engine, the rear main is a two piece seal if I recall. They sure will leak if you get them in wrong.
Good Luck

20 minutes in the driveway and 20 minutes in the water under load. No idle time, used the other engine. No, I use Edelbrock Torker 2 cams. I need the 114 degree sep with the exhaust I am running or I get reversion. Engine ran very strong, cant wait to get the other one done this winter. Yea MARK 4, It is a 2 piece seal and Im sure I got it in right but you never know with them things.

The oil pump shouldn't have anything to do with the rear main seal. The only pressure that seal is subjected to is crank case pressure. Are you running the stock type of breather system? I have seen people "upgrade" Merc's stock evacuation system and have some problems. I went through all of this on my BBC when the rear seal kept leaking. My engine builder double checked it as being fine and it still leaked. I decided the only thing to do is check it myself. I pulled the pan still full of oil and somehow the oil level was way to high. I will make a long story a little shorter. My engine builder must have filled the engine with a couple of quarts to run the oil pump off a drill in the shop. Then I got in a hurry and put the new motor in the boat. I then dumped 10 qts of oil into the new Dooley pan and marked the dipstick. It just so happened that there was no way I could suck all of the oil out of the pan during oil changes so it appeared that I was running the recommended 10 qts. Finally after two years of going crazy I called Dooley and asked how deep the oil should be in the pan and they said 3.00" equals 10 qts. I measured the depth in the pan and it was 3.76" deep!!! I felt stupid and relieved that I found the problem. I decided to run 9 qts of oil which lowered it in the pan a little over an inch. No more leaks and the motor gained 100 rpm at wot and the oil temp doesn't come up as quickly. Call it a learning experience and make sure you aren't running your rear main flooded in oil. It is amazing how something so simple can be such a pain in the ass. Good luck!!!

Man I hate oil leaks. Only way to tell is to pull it as you know. Could be from pan seal or possibly cam plug or one of the oil passage plugs. I would not take any chances to much trouble to pull in and out. Hey Wette Vette that's a good one! Live and learn.

Wette Vette. That might be something. This pan was an aftermarket (or Merc) cast pan with the stock dipstick and tube attached. I put 7 quarts in it which should have been right but maybe not. Is the fix just lowereing the level? or does the seal have to be changed anyway? I quess I wont really know till I take it apart right? Stock beathers.

It looked like brand new though. I just felt better since I had a new seal and the motor out of the boat. I installed the seal with a 3/8" offset to the cap / block parting line. That is another old trick a lot of people do to help reduce 2 piece seal leaks. In my case it was excessive oil level, but the new seal gave me some extra piece of mind.

Great thanks, Ill try it. Did you use any sealer between the seal ends? I think the one I installed was gray and I just ordered a black one that supposed to be better.