What are the most common oil leak points?

[RobH2]

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.

[Dave Neptune]

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

[RobH2]

Just when running.

[Dave Neptune]

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

[roadnsky]

Here is a good doc from Don...

[RobH2]

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!

[RobH2]

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

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?

[RobH2]

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

[nyvoyager]

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

[RobH2]

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.

[Administrator]

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

[RobH2]

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?

[Tim]

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.

[RobH2]

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

[roadnsky]

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.

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