Oil leak in 1986 OMC 4.3L

[Engineer0704]

I have a 17 ft 1986 Crestliner with a 4.3L OMC Cobra Drive. I purchased this boat used two years ago from the original owner, who rarely used the boat. Therefore, although it's an older engine, the best estimate is that it only has around 200 hours (at the most) on it. Despite it's initial lack of use, the boat has been reasonably well maintained, and in the two years I have owned it it has run like a top with little/no difficulties.<br /><br />Last weekend, following a day on the water when I ran the boat for 2-3 hours, I discovered a film of oil over the top of the engine (carb/flame arrestor, rocker-arm covers, thermostat, and associated hoses). This oil appeared suddenly - I had checked the engine that day after running it for an hour, and no oil was visible at that time. I have since cleaned the engine surface and tried to repeat the oil leak by running it at full throttle for several minutes, but the leak has not reappeared, and there does not appear to be any significant oil consumption.<br /><br />My initial thoughts were that either the rocker arm housing gasket had failed, or the valve leading from the rocker-arm housing to the flame arrestor. However, I'm not seeing any leaking from these areas now.<br /><br />In reading through my Clymer and Seloc literature, I read that engine oil leaks can happen in a boat stored with the bow angled up significantly, and that this problem is generally self correcting. The week before this problem occured, I had the boat on its trailer in my driveway, with the bow cranked all the way up. Since this is the only explanation I can think of, can anyone offer insight into this phenomenon?

 

[Don S]

Re: Oil leak in 1986 OMC 4.3L

I'd run the boat for another hour or so and see if it does it again. Sounds like you may have had some stuck rings from lack of use they may have caused some blow-by from the valve cover hoses.<br />I would think a compression check, and possibly a cylinder leak down test, would also be in order.

 

[Engineer0704]

Re: Oil leak in 1986 OMC 4.3L

I'd be inclined to agree with you, but after running it for another 30 minutes (a good portion of that at WOT) I saw little to no blow-by in the valve cover hoses, and no further evidence of any leaking. I wouldn't think that a stuck ring would fix itself, but this kind of engine problem is new to me so maybe it could.<br /><br />At this point I'll continue to operate it and watch the engine for further developments. I agree that a compression check is in order, and will do that next.<br /><br />Thanks for the input!