When To Fix The Oil Leak??

[Joe Mullee]

I have a 1983 Yanmar 3GMF. For the past several years I put between 70-100 hours on it. I do all the routine scheduled maintainance more often than the manual suggests and keep a seperate log for it. I'm a novice but do the best I can. In the fourteen years I've owned the boat there's been no engine problems.

Two seasons ago a leak developed somewhere near where the engine block and the transmission meet. I had a certified mechanic look it over while he was replacing the cutlass bearing and the propellar shaft and he told me not to worry about it. He said it was a relatively slow leak, wasn't a critical issue, and would be costly to fix due to the labor charges and the hours he thought it would take. If I recall correctly he believed it was a simple issue of replacing a seal.

My question is when should I start to worry about it and have it fixed? So far the only issue this early in the season is it seems there may be a bit more oil in the pan but I really can't say for sure. Is there a sealant I could use from the outside that might help?

Thanks,
Joe Mullee

 

[Claude L.-Auger]

Joe, it's likely the leak could come from the seal behind the rear main bearing. In order to reach it, you have to take the tranny off, then the dampler plate and the flywheel. You can then remove the housing that it's mounted in and have another seal press-fitted into it. Then of course comes the hard part of re-assembling the whole thing. It can be done without taking the engine out, but it's a bear ! I was able to do the whole thing working from the inspection door for the shaft behind the rear-cabin bulkhead. Playing contorsionist ! I did it while on a mooring and needed somebody's help to re-install the flywheel because of the weight. The 1st pix shows you the bell housing, looking inside the engine. The 2nd picture shows you all the parts carefully laid out on the galley counter: tranny, flywheel, damper, and in the lower right hand corner the shaft support with the seal. Pictures were taken after everything was cleaned. If you're not planning any real long trip, doing no more hours than what you have been doing, inasmuch as you check the oil regularly and put absorbing pad under your engine, you can run for a good long time without touching it unless it becomes quite severe. Good luck

 

[Bill Roosa]

oil is cheap, just keep her full and it will not hurt the engine.
Just keep an eye on the amount you regularly (amount/engine hours) add and if you note an increase or more oil than "normal" in the engine sump start to think about planning to do the work.

 

[Don Crowther]

Joe
How much oil are we talking about. A quart an hour or 10 hours. Is there any concern that you will runout of oil before you quit motoring? If it's only a small amount say less than a pint and it's not difficult to clean up. I would just leave it until it gets really bad. You may have to pull the engine for some other reason later on and you can replace the seal then. Have you kept track of the tranny oil. It maybe coming from that seal as well.

 

[Joe Mullee]

I'm talking like a cup, maybe less, in lost oil for the entire year. I've been out four times this year and it seems a little worse so I'll watch it closely. I know I didnt add much the last two years (105 hours in 2012 and 72 hours in 2013) and I checked it regularly. That job of Claudes looks ugly so I'd like to avoid it for as long as possible as long as it won't hurt anything.

Thanks for the help.

 

[Chris Patterson]

Are you SURE it is not that small oil line that runs beside the engine? This is a common failure on those that resemble a huge problem, but is otherwise not at all bad. Rear mains are not that common of a blow-out, but that's not to say it isn't it. Check that small oil line closely.

 

[Blitz]

All good suggestions given: rear main seal, trans seal, & oil line. I have struggled with a minor oil leak as we'll similar that you describe. The difference is that along the way I had a trans rebuilt with seals changed, damper plate replaced, the rear Main seal replaced and the oil pan gasket replaced twice. For some reason I can't get the oil pan to seal too well I my bet that is your problem as well. (Cast aluminum pan, cast steel engine block=expansion & contraction at different rates)

Monitor your loss, clean up your leaking areas, get out your mirror to see where it's coming from.

 

[gettinthere]

Perkins are famous for rear main leaks so perkins owners just live with it. A cup a year is nothing.

 

[Chris Patterson]

At least it ain't a Detroit..

 

[Benny17441]

Joe, what grade oil are you using? The thinner the oil the larger the leak and conversely the thicker the oil the smaller the leak. A thicker oil will also reduce smoking and raise compression in them older engines. It may help delay a rebuild job or rear main seal replacement. Like Bill says oil is cheap when compared to a repair job. You should not be using anything lighter than 20W-40. Some oil additives raise viscocity. I would stay away from those "stop leak" products.

 

[Joe Mullee]

Thanks for the advice. I will do another very close and more thorough check in the next week or so. I've done this in the past but haven't been able to pinpoint the exact area of the leak. A mirror would obviously help. I don't know why I didn't think of that in the past. I'm not at the boat right now but I believe I'm using Shell Rotella 15W-40. I'll double check tomorrow when I go down.

Thanks again.