1997 MerCruiser 3.0LX leaking oil.

[mike1266]

Hello all,

I've been having some trouble lately with my engine. It ran great after I de-winterized it for this season for about a month, then I started seeing some oil leaking into the bilge area. It seems to be the engine oil, as the dipstick level seems to decrease after filling it up again. So the part that really confuses me is this:

I've now topped up the oil to the "full" line twice, and when I go out for a full day on the water, it will drop down to about half way between the "fill" and "full" lines. I've also tried running it for 3 full days without topping it up. When I did not top it up to the "full" line, it seems that I had almost no leak. It only starts leaking again when I fill it up to the full line.

One more problem that I think MAY be associated with this is that when I turn off the engine, it sometimes sputters for a second or two before turning off. A couple times it's sputtered for a good 10 seconds before turning off, and this problem only appeared after I noticed the oil leaks.

Now just to clarify, the oil leak is not horrible. I would say about 10 drops of oil leaks into the bilge from the looks of it. I've tried to touch around the engine to find any signs of fresh oil leaks, and found that there was some oil towards the back of the engine. I did not find any around the oil pan, which leads me to think that it is not the oil pan leaking, and since it is to the rear of the engine it may also not be the timing cover.

I've done much searching and diagnosing but I just can't seem to find the exact location of the leak. If there are any ideas I would highly appreciate it.

Also, I am planning to use my boat until the end of July at the least, using it about 3-4 times a week. I'm at a remote location without any certified mechanics around. Would it be advisable to keep filling it up and using it, or should I leave it at the halfway point between the "fill" and "full" lines so that I do not leak more oil? OR is the problem too big that I should stop using the boat at all?

I'm learning a lot as I go, and this website has gotten me through a lot of engine problems, so thank you everyone for that.

 

[Rick Stephens]

For me, the leak is much less concerning than the dieseling after you shut it off. That can cause serious motor damage for a marine engine as often they will run or kick backwards and suck water from the exhaust into the engine - a really bad thing that can cause a breakdown from hydrolock or damage the motor from a broken piston or bent rod. Dieseling can be caused by running too rich or by timing being off.

Oil use does not have to be a leak into the bilge. Sounds like you use more oil than you leak anyway. So you are either burning it or it is going out the exhaust. I'd probably pull the plugs and look at their color and condition. And while they are out I'd do a compression check and see what the baseline condition of the motor is.

Rick

 

[mike1266]

Hi Rick, thank you for your input. I do realize that the dieseling is a problem but I am not sure how to go about diagnosing the cause. I have however noticed that if I put the engine into neutral and wait until the RPM goes under 900 to turn it off there is almost no dieseling. Would this point to a cause of the problem?

I was honestly quite worried about the oil leak- but I've ran it yesterday without filling it and got no leaks. I think I will be running the engine half full on oil while constantly checking the dipstick to make sure it doesn't go below the "fill" line.

 

[Scott06]

Hi Rick, thank you for your input. I do realize that the dieseling is a problem but I am not sure how to go about diagnosing the cause. I have however noticed that if I put the engine into neutral and wait until the RPM goes under 900 to turn it off there is almost no dieseling. Would this point to a cause of the problem?

I was honestly quite worried about the oil leak- but I've ran it yesterday without filling it and got no leaks. I think I will be running the engine half full on oil while constantly checking the dipstick to make sure it doesn't go below the "fill" line.

Letting it idle before shut off just lets the engine and combustion chambers cool down a bit after putting a load on it.

two way I lessened dieseling with my 3.0 was to

1. decarbonize the combustion chambers. GM makes a excellent cylinder and top engine cleaner, sea foam also works - pour down carb While running let it sit, start back up to big clouds of carbon in exhaust.
2. Also check your plugs might be time for a carb rebuild and you may be running lean which makes the combustion chamber a tad hotter