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Mercury 115 EFI Oil Leak questions

S

Swissfire

New member
Hi All,
I have a 2007 Merc 115 EFI that I have recently pulled the powerhead and replaced the swivel pin, oil pump, impeller, and all the seals and gaskets (powerhead to adapter plate gasket, oil pump seals, impeller seals) as well as many other parts. I put everything back together following the service manual and torqued everything down to spec. I mounted the motor back on the boat put in the motor oil. I was not able to crank it as I was waiting for control cables and harness and left the motor trimmed down. Fast forward a few weeks and I noticed that there is an oil spot under the foot and oil leaking out of the raw water intake in the foot.

Needless to say, I felt gut-punched. Before I pull the motor and put it back on the stand to pull it all apart again, it would be great to some insight into what it might be or what to look for to narrow down my search. I looked all around the midsection cowling, the powerhead, and the oil pump that I can see by the swivel pin and as far as I can see it is all dry and no other leaking. I am not sure if its motor oil or gear oil. Is there a way to tell?

motor 3.pngmotor 2.pngmotor 1.png
 
Last edited:
Gearoil has a distinct strong odor compared to engine crankcase oil. Once you know the difference you won't forget it. Smell your dipstick and see if it smells the same as what's dripping from the engine.
 
fitz73222 said:
Gearoil has a distinct strong odor compared to engine crankcase oil. Once you know the difference you won't forget it. Smell your dipstick and see if it smells the same as what's dripping from the engine.
Click to expand...

Thanks fitz73222! I did a smell test and it does smell different. When I pulled the dipstick to compare the smell, I noticed that the color is wildly different. The oil on the dipstick was clear (new oil and never cranked the motor) compared to the oil on my finger in the pic above, which is very dark.

Feeling much better that the leak is likely coming from the lower unit vs needing to pull the powerhead again.

When searching through the forums most seem to be fixed by a shift shaft seal.
Are there any other seals that I need to be on the lookout for?
Could it be leaking from me not doing the impeller replacement properly?
 
You can drop the lower unit and take it to repair shop to have it pressure tested. You will quickly know where the leak is coming from. It can be something as simple as a bad or leaking fill or vent screw seal washer. The only other places are driveshaft seals, propshaft seal, or shiftshaft seal
 
Just out of curiosity, I saw a video that said I need to drain the motor oil to put the lower unit or the oil would dump out.

I feel like this isn't true but I wanted to check before I make a mess.
 
Update:
I pulled the lower unit, drained the oil (which looked in good shape) sprayed the LU with soapy water and pressure tested it. I didn't see any leaks or bubbles but I can hear a leak coming from inside the raw water intake.

Any one have any ideas on what that could be?
 
If oil is leaking at prop, more than likely a carrier bearing seal or o-ring, pressurize 8 psi. spray soapy water all around where prop. shaft comes out . pull water pump housing and bottom plate, then spray that drive shaft seal , then spray shift shaft seal.
 
Update:
Pulled the impeller and impeller base so that I could get down to the driveshaft seals and redid the pressure test. The drive shaft seals were bad. Replaced the driveshaft seals and retested. the pressure stayed at 12 psi for 5 min (as recommended in the manual).

Thanks everyone for your help.
 
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