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Old 09-19-2017, 06:28 PM   #1
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Default Oil Leak

So, my recent experience has been that boat engines leak oil and leave a mess in the bilge. I'm trailering the boat so, I can bring it home and swab out the bilge with a old towel and degreaser.

Since buying the boat, she is loosing a lot of oil, roughly a quart in 10 hrs running time and very gentle running, no towing, light loads, low RPM. It's not being burned, there is no smoke at any RPM, no oily smell. But there is a puddle in the bilge, so it's leaking, not being burned. Not leaking around the dipstick fitting, or the oil change fitting.

Has anyone ever used an automotive type "stop leak" type of product. Do they work on a marine engine? Or, is it just a matter of topping it up, and swabbing it out?

Any suggestions would be appreciated. Thanks
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Old 09-19-2017, 07:35 PM   #2
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If you can reach it, check the drain plug to see if it's leaking there. I would rather find the leak and fix it than putting any additives on the oil.
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Old 09-19-2017, 09:25 PM   #3
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Well, it has the Mercruiser quick change oil drain system. The rubber hose has a clip on the end and actually lays up against the motor, so it's not laying in the bilge.

Where that hose attaches down at the oil pan is not leaking. I have wiped it again and again, and no real oil on the rag to speak of.
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Old 09-19-2017, 10:13 PM   #4
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Does it leak oil when the engine is not running? If no it's probably a crank seal.

Can you tell if the leak is near the front or rear of the engine?
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Old 09-20-2017, 02:16 AM   #5
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Just wiping under the engine with a rag, i felt most of the oil was on the front right (starboard) side. I gave it a good long run tonight, and again, very moderate speeds, under 3,000 the whole way.
I'll see what the dipstick looks like tomorrow.
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Old 09-20-2017, 02:52 AM   #6
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What engine do you have? Sounds like it could be the dipstick tube leaking where it enters the oil pan.

Try cleaning the bilge and lay down some paper towels and let it sit for a day or two then look for oil spots and their location.
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Old 09-20-2017, 11:07 AM   #7
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Try tightening the oil pan bolts. Corner bolts should be torqued to 18 ft/lbs, and remaining bolts to 106 in/lbs. That's not very tight, and the bolts can work themselves out with normal vibration. Checking these bolts is fairly easy with a 3.0 engine, but more challenging with 5.0. I'm not sure which engine you have.
You've probably already checked that your oil filter is tight.
I have a wireless borescope that is great for these types of problems. It is compatible with my ipad, has adjustable light, and HD video. I think $40 on amazon.
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Old 09-21-2017, 09:09 PM   #8
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I've got the 4.3 V6. In the short run, i did the paper towels under the engine thing, and we'll see if there are telltales signs.

I'm fairly basic with a wrench, but a check of the oil pan bolts might not be out of the question. I've got a torquewrench around here somewhere. See what happens.
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Old 09-22-2017, 12:53 AM   #9
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Caution you need two different torque wrenches. Ft-lbs for four corner bolts and inch-lbs for all other.
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Old 09-22-2017, 01:54 PM   #10
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thanks for that key piece of info. let's see what happens. in the meantime, I'll keep mopping it up.
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Old 09-22-2017, 03:09 PM   #11
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Have you been able to determine if it leak just sitting?
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Old 09-23-2017, 02:31 PM   #12
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Will be some time. Boat is laid up for the better part of the next week. Schedule takes me elsewhere. We'll see, but to the eye it doesn't appear to be leaking when not running. The paper towels will tell.
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Old 09-23-2017, 03:36 PM   #13
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Quote:
Originally Posted by The Pirate View Post
Will be some time. Boat is laid up for the better part of the next week. Schedule takes me elsewhere. We'll see, but to the eye it doesn't appear to be leaking when not running. The paper towels will tell.
Understood, if it doesn't leak sitting that rules out a leaking drain plug or rusted out oil pan. What remains is oil pan gasket, dipstick, front or rear crank seal, corner of a head gasket, intake gasket, oil sendor, valve cover gasket.

If I recall the leak is loosing a fair amount of oil in a short time so oil pan gasket, crank seal are most likely.
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Old 10-10-2017, 04:21 PM   #14
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OK, had a chance to get back into the boat, and the oil leak, over the long weekend. Now I can see that the majority of the leak comes while running. It comes from low on the engine (4.3 ltr.), there is no oil evident on top.

I think it's pretty substantial in that it's about 3/4 cup or so, after only about 2.5 hrs. running time on it; very light loads; 2600 rpm, cruising speed. Thru the end of the season, I'll see about rigging up some sort of drip pan using one of those, throw away oven roasting pans, just to keep it contained, and look to keep the oil topped off.

But long term, i have to think the boat, though very lightly used (180hrs, total, now) was not well maintained, and I imagine it was used for towing, with nobody looking at the oil. Cannot be good for the motor.

The realist in me says, this is something like a front crankshaft seal. I would be lucky if this was only an oil pan gasket.

Any thoughts are greatly appreciated.
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Old 10-10-2017, 05:02 PM   #15
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Toss a few oil absorbing sheets down in the bilge and replace them after each outing. It'll be easier than a roasting pan in the long run.
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Old 10-10-2017, 10:07 PM   #16
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Front crank seal is easier than the pan gasket. Could also be rear main seal which requires pulling the engine. Do you have a remote oil filter kit? Mine had leaking hoses.
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Old 10-11-2017, 09:28 PM   #17
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no on the remote oil filter. I guess simplest thing to do is go with the oil absorbing pads for now.
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Old 10-11-2017, 09:49 PM   #18
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Quote:
Originally Posted by The Pirate View Post
no on the remote oil filter. I guess simplest thing to do is go with the oil absorbing pads for now.
Yep basically what I said in post #6
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Old 10-11-2017, 11:29 PM   #19
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Easiest way to trace an oil leak that's not easily visible to the eye, put dye in the oil.
Get yourself some of these, and the UV flashlight.
https://www.amazon.com/Tracer-Produc.../dp/B000JFHNTM

See article here => Finding Oil Leaks
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Old 11-07-2017, 05:41 PM   #20
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So, was able to get back to the boat past few days. Had put towel under motor and leak is definitely coming from the front, and only when it runs. Clearly defined spill on rag, no spray otherwise in compartment.

I think that leads to the oil pan gasket. I can feel oil when I run my hand under motor and I think if it was main seal, there would be more "spray" around compartment.

While on the 'net, saw an add for, "The one oil sealer that actually works". Pretty expensive, $58 for 8 oz. of liquid. But supposed to be the only one which does not just thicken the oil, but uses polymers to restore the gasket material. Tech guy said he used it on both engines of his Formula and it worked, so it must be true, right?

I'll try it and see, cheap first step. Oil pan gasket might just be long term gripe. I'll get some oil absorbing sheets, because it will probably always leak some.

Otherwise, fuel consumption is very good, starts up easy and runs smooth. Have run some PRI-G thru it to clean things up. I've had good luck with that on other boats and cars.

I'll try this and let everyone know how it works. Any other thoughts are always appreciated.
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