Quarter sized hole in imco lower
 

I have an imco lower unit and was looking it over after running. I noticed on the right side of the drive below the cavitation plate that there is a quarter sized hole in the casing. I lost no oil with this but know this is not normal. I can look in and see casting marks and there is casting mark on an inner section directly behind this hole that looks to be the same size. Anyone have an idea of what this is or what happened? I was thinking grind it out and maybe do some welding to repair this thing.

Call IMCO before you do anything..

On the forward section of the lower, there are casting plugs. If the case is clean and polished, the plugs become virtually invisible. When the lower gets some wear on it, especially in salt water, you can easily see them. They are about the size of a quarter. Is it possible that one of these plugs fell out? Can you post a picture?

I agree with Vinny, casting plug, you can see where they are welded on the inside. I would call Imco.

Thanks guys. I will post a couple pics this weekend. My first impression was something like that due to the perfect size and shape of the hole. Fully intend to contact imco next week. Nice to have such a knowledge community to help each other out.

Joel

Ok, Guys. Got some pics of this hole. Any ideas or fixes?

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Well, you got me on that one. To the best of my knowledge, there is no casting plug in that spot. I dont know why there would be a hole there. Even though this is a very long shot I can speculate... Keep in mind it is very difficult to tell from a picture, My guess is that hole may be the spot where the vertical shaft lower bearing is located. If someone rebuilding that lower had a problem getting the cage of the bearing out, especially if the Imco bearing had been replaced by a Mercury bearing, in despiration, they may have drilled through the case to help get the cage out. The other possiblilty that comes to mind is the bearing failed and damaged the case, forcing someone to repair the case with some welding. In either case, maybe the weld didnt hold?

Vinny, I think that hole is forward of the vertical shaft.
Bones, can you measure from the front edge of the housing back to the center of the hole. I have an new Imco lower sitting here. If I had the measurement, I could look to see what is inside at that point. That may tell us something.

Dick

Thanks for taking a look guys. So far not what I wanted to hear. I will get some measurements today and see if something can be figured out. I will say that when I look in the hole there is nothing inside and that no oil has leaked from the drive from that point. It seems like this is just an empty cavity. I don't know at this point, but hoping I can weld instead of ordering a new imco casing.

Dick,

The hole is about 7 5/8 for that leading edge just above the upper portion of the curve that leads to the cone directly inline the hole. Any input and advice is appreciated.

Joel

Joel,
Here is some pics of the -3" shorty. I marked the side of the case at 7 5/8". You can see it lines up with the water cavity at the top of the housing (mating surface). Depending on how far down from the mating surface the hole is it could be in two different cavities.
One picture shows the water passage and an oil passage (inside the circle where the oring goes). If you look at the inside of the water passage, it turns as you go deeper. Your lower is taller than this one so that turn should be deeper into the housing. I suspect that it goes into the water passage. You said you did not find any oil leaking there so I have to believe it is in the water passage.
Have you tried to put some air to the hole? Or put some air to the water pick up slot and see if it any leaks out of the hole. If it is in the water passage, I would just weld it back up, but try not to over heat anything while doing it.

I hope that helps,
Dick

Thanks Dick,

This is reassuring. I will try what you have suggested and see what happens. I am also going to contact imco and see what they say as well now that I feel better about it. I figure I have 110 days and counting to get this straight for boating season. I appreciate your time and knowledge looking into this for me. I will keep this forum open and post what the outcome is for anyone that may experience the same thing in the future.

Joel

You're welcome Joel. Let us know how it goes.

Dick

Ok guys got the word from IMCO finally about this hole. It is a sand casting hole that has popped out. They said weld it up and go on with it no problem as that is what they do after casting. Just gotta figure out what the best replacement stock will be and cut a plug to fill this thing. I was thinking about just using a hole saw and resizing the hole then cutting a plug with the same bit and sticking it in there. Anybody ever done anything like this?