Gear Oil In My Bilge

[twerth]

My boat has a new problem, or combination of problems I'm hoping to get some thoughts on. 2003 Mercruiser 3.0 with Alpha 1 Gen 2. The boat's new to me (bought it last fall), and the first several times I had it out, the bilge stayed almost completely dry. But when returning from the last couple of trips to the lake, I noticed that I'd drain 1-2 quarts of water when I removed the plug. And to make matters worse, there was oil in the water.

My hull is solid so I suspected a leak in the cooling system as the water source. I put a piece of masking paper under the engine over night to check for leaks. No oil drips from the engine, so I suspected and confirmed that it's gear lube.

I ran it on the hose in the driveway and I was able find a steady drip at the left rear of the engine behind the exhaust pipe. It appears to be clean water only. I can't see exactly where it's coming from because the exhaust is in the way, so if there are usual suspects in that area, I'd be interested to hear it. FWIW, the manifold gasket and the exhaust elbow gasket are both new.

The source of gear lube in the bilge was still a mystery, so I drained it. The lube was fresh this spring, but what came out looked like a milkshake. So I still don't know how the gear lube is getting out, but water's also getting in.

End of the day, I suspect I've got two separate issues here, but I'd love to hear what people with more boat experience think. Appreciate any input and/or ideas on things to check.

 

[cyclops222]

Sure sounds like a lot of new parts were done ? Head gasket let go to mix oil & water ?
Time for Racerone Compression Tests.

 

[twerth]

Sure sounds like a lot of new parts were done ? Head gasket let go to mix oil & water ?
Time for Racerone Compression Tests.

I replaced the manifold gasket because I thought it was leaking (sucking air). That may or may not have been the case. Still chasing that one down.

My engine oil is clean. No water is getting in there. It's the gear lube that has issues. The head gasket or the manifold gasket could be the source of the water leak though. I'll need to use a mirror so I can see the back of the engine while it's running.

 

[cyclops222]

To make matters worse. There was oil in the water ?
You have a patched up engine that was sold to you.
Very bad luck is beginning to look like your problem.

 

[Chris1956]

Gear lube in the bilge on a MerCruiser usually comes from a leaking yoke seal on the driveshaft. See if you can detect the gear oil by sticking your finger on the bellows from inside the boat, or pull the outdrive and see if gear oil is in the driveshaft bellows.

As for the water, I am not sure what is in that area on the IL4 engines. Could be a leaking manifold, partially popped freeze plug or something else. Stick a mirror down there and run the engine and look. try it in a flusher device and see if you can spot it.

 

[Lou C]

Your drive could be sucking in water when it cools which will force gear lube out at the weakest part of the system, which may be the hose to the lube monitor bottle.
Also you need to use a mirror or inspection camera to find out where the water leak is coming from, it could be from the elbow to manifold gasket, the hose clamps on the rubber exhaust hoses, the connection of the exhaust pipe to the transom mount, etc.
That's one of the real headaches with I/Os; there are so many places where they can leak water, both thru the transom mount, and from the engine cooling system.

 

[Scott06]

My boat has a new problem, or combination of problems I'm hoping to get some thoughts on. 2003 Mercruiser 3.0 with Alpha 1 Gen 2. The boat's new to me (bought it last fall), and the first several times I had it out, the bilge stayed almost completely dry. But when returning from the last couple of trips to the lake, I noticed that I'd drain 1-2 quarts of water when I removed the plug. And to make matters worse, there was oil in the water.

My hull is solid so I suspected a leak in the cooling system as the water source. I put a piece of masking paper under the engine over night to check for leaks. No oil drips from the engine, so I suspected and confirmed that it's gear lube.

I ran it on the hose in the driveway and I was able find a steady drip at the left rear of the engine behind the exhaust pipe. It appears to be clean water only. I can't see exactly where it's coming from because the exhaust is in the way, so if there are usual suspects in that area, I'd be interested to hear it. FWIW, the manifold gasket and the exhaust elbow gasket are both new.

The source of gear lube in the bilge was still a mystery, so I drained it. The lube was fresh this spring, but what came out looked like a milkshake. So I still don't know how the gear lube is getting out, but water's also getting in.

End of the day, I suspect I've got two separate issues here, but I'd love to hear what people with more boat experience think. Appreciate any input and/or ideas on things to check.

All boats will have some oil in the bilge...

Do you have a lube bottle on the engine? watch the level there to see if it is dropping. If it is the small rubber line back to transom can leak or if the input shaft seal of the drive leaks into bellows it can eventually get enough in there to leak into bilge.

Motor oil can come out of engine in several places like filter , distributor , rear main seal of just being sloppy when you fill the oil..

the water leaking out under the manifold is typically where 3.0s freeze crack you may see with a mirror or have to remove the manifold. That area where head and block meet it the top of the water jacket on block and typically where 3.0s crack. Do you have water in the engine oil

 

[twerth]

All boats will have some oil in the bilge...

Do you have a lube bottle on the engine? watch the level there to see if it is dropping. If it is the small rubber line back to transom can leak or if the input shaft seal of the drive leaks into bellows it can eventually get enough in there to leak into bilge.

Motor oil can come out of engine in several places like filter , distributor , rear main seal of just being sloppy when you fill the oil..

the water leaking out under the manifold is typically where 3.0s freeze crack you may see with a mirror or have to remove the manifold. That area where head and block meet it the top of the water jacket on block and typically where 3.0s crack. Do you have water in the engine oil

Thanks to all for the quick responses. Looks like I've got some things to check out.

Scott, my engine oil is clean, clear and still up at the full mark on the dipstick. I had also placed a large piece of paper in the bilge under the engine to see if any drips materialize. It came out clean. The oil I'm finding in the bilge is definitely gear lube. It's stinky!

Thanks again.

 

[Chris1956]

OK, post 5 lists some likely causes.

 

[twerth]

OK, post 5 lists some likely causes.

Yup. I appreciate the help!

 

[tank1949]

I replaced the manifold gasket because I thought it was leaking (sucking air). That may or may not have been the case. Still chasing that one down.

My engine oil is clean. No water is getting in there. It's the gear lube that has issues. The head gasket or the manifold gasket could be the source of the water leak though. I'll need to use a mirror so I can see the back of the engine while it's running.

If you have a lube reservoir, is it possibly leaking? Is boat fresh or salt water used. Do you have good compression?

 

[twerth]

If you have a lube reservoir, is it possibly leaking? Is boat fresh or salt water used. Do you have good compression?

No lube reservoir, fresh water and compression is between 160 and 170 on all cylinders. I checked compression with the throttle closed, so that might go up a little if done correctly.

I'm leaving town for a week, so it'll be a while before I'm able to spend more time on this. I'll circle back once I've had a chance to try some of the suggestions I've received. Thanks!

 

[tank1949]

No lube reservoir, fresh water and compression is between 160 and 170 on all cylinders. I checked compression with the throttle closed, so that might go up a little if done correctly.

I'm leaving town for a week, so it'll be a while before I'm able to spend more time on this. I'll circle back once I've had a chance to try some of the suggestions I've received. Thanks!

Have you tested transom for rot. IOs are bad about transom rot. Also. invest in a pressure tester.

 

[Grub54891]

the water leaking out under the manifold is typically where 3.0s freeze crack you may see with a mirror or have to remove the manifold. That area where head and block meet it the top of the water jacket on block and typically where 3.0s crack. Do you have water in the engine oil

Mine had that crack, along with all the core plugs popped out. Yeah. Every core plug. The po didn't winterize. I took a chance, pulled the motor and dremmeled out the crack a bit, sealed with jb weld and painted the area. Replaced the core plugs and ran it alot and hard for the summer. No water in the oil, and ran perfect. Still going 7 years later. Luck was on my side! I thing it froze and then thawed out before the big freeze for the winter.

 

[tank1949]

the water leaking out under the manifold is typically where 3.0s freeze crack you may see with a mirror or have to remove the manifold. That area where head and block meet it the top of the water jacket on block and typically where 3.0s crack. Do you have water in the engine oil

Mine had that crack, along with all the core plugs popped out. Yeah. Every core plug. The po didn't winterize. I took a chance, pulled the motor and dremmeled out the crack a bit, sealed with jb weld and painted the area. Replaced the core plugs and ran it alot and hard for the summer. No water in the oil, and ran perfect. Still going 7 years later. Luck was on my side! I thing it froze and then thawed out before the big freeze for the winter.

Indeed, and now most Chevy blocks can be welded by a PROFESSIONAL welder. I had 350 welded and it worked fine.

 

[airshot]

No lube reservoir, fresh water and compression is between 160 and 170 on all cylinders. I checked compression with the throttle closed, so that might go up a little if done correctly.

I'm leaving town for a week, so it'll be a while before I'm able to spend more time on this. I'll circle back once I've had a chance to try some of the suggestions I've received. Thanks!

Check your comp gage, my manual calls for 150 lbs per cylinder.

 

[twerth]

A bit of an update. I found the source of the oil leak. It was motor oil leaking around the oil filter gasket. The filter was tight, but I took it off, inspected the gasket (found nothing wrong), cleaned and reinstalled and now it's fine.

I also changed the gear lube in the lower unit. I've had it out once since then, and everything seems to be fine. No signs of water in the lube, so I'll keep an eye on it going forward.

I still have the water leak though. I haven't been able to pinpoint it, but it's coming from below the head, and I think maybe from the sterndrive? I'll have to remove some stuff so I can get a better look, but it's a small enough leak that it's not keeping me from using the boat. I'll check back if I figure this one out.

Thanks for your help!