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Rebuilt Mercruiser 140 has a rear main oil leak

buckz6319

buckz6319

Regular Contributor
I have completely rebuilt the 85 Mercruiser 140 and she runs like a top! however the new 2 piece rear main oil seal(Fel-Pro brand and it came with the kit) is either leaking or the pan gasket is, it's a 4 piece pan gasket.

This appeared within an hour of the first start up after the rebuild. I installed the seal by the book(shop manual) proper off set, lip facing the correct way and used the recommended sealant in the correct areas.

I decided last week to remove the pan and have a look at the seal and gasket. I couldn't find any areas of the oil seal or pan gasket that appeared to have damage or not properly installed, so I put it all back together and started her back up yesterday only to find that I still have the oil leak.

I did not see any engine oil on the backside of the flywheel, so it appears to be Dripping straight down.

The Mercruiser is still on the ground and I will not install it back in the boat until I can figure out what to do to fix this issue

any input would be appreciated!
 
I thought I would add some pic's, of what the 2 piece rear main seal looked like in position, before I removed the oil pan and main cap




 
I would purchase a MERCRUISER new rear main seal and give it another try.

It may just be the fellpro is not exactly the right size.........The Merc should be!!
 
The grooves in the seal appear correct for a left hand rotation motor so it could just be a undersized seal. any crankcase pressure should escape thru the 1/2 hole in the valve cover
 
Bt Doctur said:
The grooves in the seal appear correct for a left hand rotation motor so it could just be a undersized seal. any crankcase pressure should escape thru the 1/2 hole in the valve cover
Click to expand...

I'm getting great crankcase pressure out the valve cover tube, no problem with that. The undersized seal I didn't think about...
 
I am not sure a seal surface should be "polished"

I thought that they used a 220 grit or maybe 100 grit and simply sanded it.. The seal needs a somewhat ground surface to wear into........


Maybe these days scotchbrite would work....


Most sealed surfaces are not polished...........
 
At this point I would contact the machine shop.............don't try to figure this out yourself.......

you paid good money for all this stuff so let them give you advice............
 
kghost said:
At this point I would contact the machine shop.............don't try to figure this out yourself.......

you paid good money for all this stuff so let them give you advice............
Click to expand...

Well, It's on me, no warranty when not assembled by machine shop...but I have some hot rod builders that could give some input on this, maybe I'll talk with them...
thanks Jack

and if you feel like it? take a look at my boat forum and if your interested? we could use your advice over there
www.chaparralboatxchange.proboards.com
 
OEM...got the one that you sent me the link to...thanks! I installed the seal without the offset, so I could get the right amount of crush when installing the main cap. I also used sealant where required.
 
I am not sure installing without the offset is a big deal. The manual shows to do the offset. The seal will "crush" either way.

My suspicion is the Fell pro seal may not have been the correct size....it is not uncommon for a after market seal to not be exactly the right size.

This is one of the reasons when I do work on any mercruiser I use OEM parts as often as I can.
Of course there are many situations that any aftermarket part will work fine and in those cases I will substitute.
 
kghost said:
I am not sure installing without the offset is a big deal. The manual shows to do the offset. The seal will "crush" either way.

My suspicion is the Fell pro seal may not have been the correct size....it is not uncommon for a after market seal to not be exactly the right size.I agree.

This is one of the reasons when I do work on any mercruiser I use OEM parts as often as I can. I agree and should do the same..
Of course there are many situations that any aftermarket part will work fine and in those cases I will substitute.I agree also with this comment
Click to expand...

thanks Jack for your input and I'll keep posting updates on this project
 
I wanted to update this thread...

I have now gotten to the point with the chap where I'll make my first splash in July if not sooner. The Mercruiser is back in the boat, new OEM 2 piece oil seal installed and not leaking, installed a new gimbal bearing and carrier, aligned the engine, installed a new OEM impeller and gaskets, installed the Alpha one gen 2, wired all the accessories, installed the trim pump, bled the trim pump, checked the operation of the trim pump, installed the blower and checked that it works, put water to the outdrive and started her up. I feel confident that everything is working properly at this point

I just have to do a few more things before I take her to the lake, like get a bilge pump and all the safety equipment ect, put my trailer tag on, boat decal on, get a spare tire ect...

I hope she does good on her first wet test...I have worked hard on this project
 
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