What are the most common oil leak points?
 

I appear to have an oil leak. My engine is crammed so tightly into a hole that I can't get around it to see anything. I can't tell where it's coming from. I'm going to buy one of those cameras with the small flexible metal hoses so I can look around.

But until then, are there some typical places that an engine will begin to leak? Or, is everything fair game and it could develop a leak anywhere with equal probability?

I did pull my water pump off this spring in my "water in oil" fiasco, but I used a new gasket when I remounted it. Is that a place where a lot of oil can leak?

I lose about 1/2 quart per hour. I don't have smoke but I am seeing it in my bilge.

That is a lot of "leakage" and may just be leaking under pressure at the rear seal, a good first place to look. There are a couple of oil galley access points on the carb side of the block and the drain plug to give a good look.

Does it leak when just sitting or only when running?

Dave Neptune :cool:

Just when running.

Also check under the water pump as there is a seal to the crankcase too.

When looking with a mirror or camera look for a clean path to the drip that will lead you to the leak as the leak will leave a "clean streak".

Dave Neptune :cool:

Here is a good doc from Don...

Dave and Jerry, thank you. Very helpful.

I'm assuming that doing a rear main seal replacement is not an easy task should that be it!

I did pull my water pump and remount it. It's possible that some debris got lodged under the gasket and it's not sealing. Can that much oil leak out of that power take off?

Unfortunately, I think I've found my leak and it's not good. It looks like I have a crack in my block, or in the part you see in the video I've posted. At the end I backed out slowly so you could see where in relation to other transmission parts the crack is. I placed paper towels all over and in this spot it was wet with fresh oil when I pulled them out.

I used the scope afterwards to look and see. What I need to do now is set the scope up and then run the engine to see if oil is seeping out of the crack or if it's coming from above and just "coincidentally" running there. I don't think it's a coincidence thought. I think I have a crack.

Can I clean and apply something to that crack to seal it temporarily? I can't afford to pull the engine right now and rebuild or replace it.

This looks like an "engine killer" to my untrained eye. What do you guys think?

https://vimeo.com/348068083/8acc4ae559

If I am seeing this correctly you are at the tail shaft output on the gearbox - not a cracked block - but I'll defer to others with more knowledge

Yes, I'm at the rear of the transmission where the drive shaft connects.

I guess it's really not the block, but it is a cast part of the engine I think. I'm not sure if the bottom part of the engine is a cast part or an oil pan. I've never seen one out of a boat nor have I worked on mine more than changing a head gasket and dealing with auxiliary parts.

I do believe it is a crack though and I'm concerned.

This is the oil pan.

If you look at the panoramic views of the engine here, you can get a sense of what's what.

Bill

Thanks for this Bill. It would be nice to have a slightly "under view" but this is great. I know where to find this handy viewer now and should have looked better and found it earlier.

So my apparent crack is under the rear connection that has 6 bolts, in the part that makes up the engine bottom just where it begins to roll around from vertical to underneath. It's right below the bottom center bolt. I wonder how it could crack there? Age?

I don't even what to think about how to fix it. Suggestions?

http://nvision.s463.sureserver.com/public/Crack2.jpg

You will need to pull the engine and remove the oil pan. Once the oil pan is off, you can either repair your current oil pan or replace it. You will need oil pan gaskets, rear flange gaskets and flywheel gasket. While the engine is out, you might want to also replace the thrust bearing and rear oil seal, or do any other repairs or upgrades that are hard to reach while the engine is in place. Depending on how much room you have in your boat, you can probably do all of this in your boat.

Yea, I was afraid of this. Thanks for the detailed info. I have some serious thinking to do now.

As a TEMPORARY fix I think you could try to seal (or at least slow) the leak until you can do the full Monty?

Ha, that's what I was thinking. I was embarrassed to mention that here for fear of users telling me how "bad" an idea that would be...lol...

I was just at the boat and I used some solvent to wipe the crack and get it really clean. I wanted to see if it was weeping oil without the engine running. If it's not weeping, I was going to try an engine crack repair epoxy. J-B Weld is one but there are others.

My thought was that if the crack was weeping, nothing would ever stick. But, if it's not weeping, I'd wire brush the crack, clean it and then put a patch on it. It might just stop or slow it until the fall so I'd not lose use of the boat this summer.

My main issue is my son is getting married this fall and we have a huge wedding bill. I can't afford to drop a lot of money into my engine right now. I'm hoping I can patch this crack and have it last until, like you say, "the Full Monty."

Watching the video, it looks like the crack runs up the back of the oil pan to the lower bolt hole for the rear flange and that is causing oil to leak around the lower flange bolt. You can try to seal the crack, but if the crack starts at that lower bolt it will be difficult to stop it from leaking around the bolt. In this case tightening the bolt would make the leak worse. If you can get the crack sealed, maybe installing the lower bolt with a lot of thread sealant or some type of caulking would help.

I've hard is it to pull that rear flange off? I think you are talking about the part with the 6 bolts. I'd like to have a look at it. Can I do what with the boat in the water and the shaft attached?

Yes, the rear flange is the part with six bolts. There are actually two parts, the one closest to the engine holds the thrust bearing and the outer one holds the rear oil seal. The three upper bolts attach to the reversing gear housing, the three lower bolts attach to the oil pan. To remove the flange, the output coupling does need to be removed. You may be able to do this with the engine in place if you have room to work. There is a good description of how to remove the output coupling in the Moyer manual.

Thank you Tim. I'll have a look at it. I have very little room is my only problem. Let me see what I can find out.

I'd like to pull it off and see if the crack extends to the bolt hole as was mentioned. I hope not but that seems likely as to how the crack started.

I hate to jury rig a patch but I just can't afford to pull the engine right now and we've had great air this year. I don't want to lose use of the boat.

It sounds like you are going to need to pull the engine to get the rear flange off and inspect/seal the crack. At that point you may as well replace the oil pan or have it repaired. If you had the parts on hand, that could be done in a weekend.

Yep, I hear you. I need to start wrapping my head around it.

On the bright side, it is not the "engine killer" you were worried about.

I hear you Tim. Thanks. I'll report back what I decide to do.

Not a lot of $$$$, just a big pain. One does wonder why that would crack?