4.3 crankshaft/housing oil leak - next steps?

S

ShoalSurvivor

Petty Officer 1st Class
Joined
Aug 1, 2012
Messages
233
greetings all. found oil in the bilge and isolated it to the crankshaft seal or housing. Does not appear to be an oil pan issue. I found no obvious corrosion around the housing (from what I can reach).
Screenshot 2025-05-28 at 9.08.25 AM.pngScreenshot 2025-05-28 at 9.08.35 AM.png
Lost about 3 oz of oil after a 3-day weekend - running ~ 8-12 hours at various speeds. The leak displayed in the photo is after cleaning and running to warm for about 4 minutes. I have done some research, but would appreciate experienced input here.

Is there more that I can diagnose before pulling the seat bench out for frontal access? Camshaft assembly is just above floor level, so I think I can access all of it once the bench is removed.

Is there a likely repair (ie. replace housing/seals) based on what can be seen here?
Does the repair likely require 1) removing engine, 2) removing drive, or 3) just gaining frontal access and removing belt/pulleys to access cover?

Am I in imminent danger of sudden, rapid loss of oil (ie..ruining the engine) or is this something that I can put off until after summer by managing oil with absorption pads and maintain oil level? We have many plans for wakeboarding and short nighttime cruises (concerts by boat) and I'll have time this fall for repairs.

thanks,
Michael

1999 Stingray 190LX
2004 Mercruiser 4.3L 225hp 4bbl
Quicksilver repower: SN: 90004747 Engine PartNo: 807736R11 date: 03252004 (original engine SN: L332123)
Alpha 1 Gen II - Transom: 0L517680 Drive: 0L192679 1.62 R (1.81R scratched on top) (original drive SN: L40356)
 
Scott06

Scott06

Admiral
Joined
Apr 20, 2014
Messages
6,871
ShoalSurvivor said:
greetings all. found oil in the bilge and isolated it to the crankshaft seal or housing. Does not appear to be an oil pan issue. I found no obvious corrosion around the housing (from what I can reach).
View attachment 408160View attachment 408161
Lost about 3 oz of oil after a 3-day weekend - running ~ 8-12 hours at various speeds. The leak displayed in the photo is after cleaning and running to warm for about 4 minutes. I have done some research, but would appreciate experienced input here.

Is there more that I can diagnose before pulling the seat bench out for frontal access? Camshaft assembly is just above floor level, so I think I can access all of it once the bench is removed.

Is there a likely repair (ie. replace housing/seals) based on what can be seen here?
Does the repair likely require 1) removing engine, 2) removing drive, or 3) just gaining frontal access and removing belt/pulleys to access cover?

Am I in imminent danger of sudden, rapid loss of oil (ie..ruining the engine) or is this something that I can put off until after summer by managing oil with absorption pads and maintain oil level? We have many plans for wakeboarding and short nighttime cruises (concerts by boat) and I'll have time this fall for repairs.

thanks,
Michael

1999 Stingray 190LX
2004 Mercruiser 4.3L 225hp 4bbl
Quicksilver repower: SN: 90004747 Engine PartNo: 807736R11 date: 03252004 (original engine SN: L332123)
Alpha 1 Gen II - Transom: 0L517680 Drive: 0L192679 1.62 R (1.81R scratched on top) (original drive SN: L40356)
Click to expand...
Doubt you are in imminent danger of loosing oil pressure unless you dont top off. Biggest issue is the bilge water will get oil contaminated (more than normal).

You may want to search on here. one of the former mods Chris had a similar issue with a similar vintage 4.3 that I think ultimately was cause by the timing cover or oil pan as there was a ridge on one or the other that caused the leak despite several reseals.

most of the time to track this down you need to clean the engine with brake cleaner then watch the leak. A UV light can be helpful here. I had a antifreeze leak on a car and put UV dye in the AF, cleaned every thing off and then was able to easily find the leak with the UV light. I found the oil (valvoline) is also slightly UV reactive. Not sure if they make a dye that is ok to put in oil

the things to look for are the timing cover oil pan rail seals and front crank seal. Im not sure if they can be done in the boat, but if you can arrange the lifting mechanism I think you would be better off to jank it , do the repair and then run on the ground to make sure it is not leaking before re-install. This sounds like a lot of work but isnt that bad to run an engine on a pallet or even the ground
 
S

ShoalSurvivor

Petty Officer 1st Class
Joined
Aug 1, 2012
Messages
233
Scott06 said:
most of the time to track this down you need to clean the engine with brake cleaner then watch the leak.
Click to expand...
Thanks Scott.
I have isolated the drip from under the crankshaft a seen in the photo. no oil above, none below. That drip is coming from the block side, right in the center of the shaft. Looks like seals to me, but I've read that seals are unlikely source.
I cannot get a better view in that space than what I was able to photograph, so I'm not sure how I could isolate any further without pulling it apart.
 
K

kenny nunez

Captain
Joined
Jun 20, 2017
Messages
3,352
After the engine is out look closely at the seal surface on the crankshaft. It may be grooved or there is a build up of rust which will cause pitting. Either way you can repair the surface with a Speedy Sleeve that will provide a smooth stainless surface. They come in many sizes and their web site is easy to understand.
 
Scott06

Scott06

Admiral
Joined
Apr 20, 2014
Messages
6,871
ShoalSurvivor said:
in there any chance that I can repair this without removing the engine? I’d prefer not to, if possible.
Click to expand...
Not sure - I think this is the parts list for your engine -


it shows a plastic timing cover. these covers are single use and they dont sell the seal separately. of course these are just Gm parts not sure if the seal is available via automotive.

As long as you dont have to drop the pan to get the cover on off and there is room in front maybe.
 
You must log in or register to reply here.
Top