Best way to repair corrosion hole in a Honda OB?

So I have just come into a very nice deal on an 1980's vintage Honda BF75, at least I think it's an `80's model.

Anyway... as can be seen in the picture this was a saltwater OB and has a nice little hole in the casting. From what I have found a thickened epoxy is a good candidate for this type of a repair but I wanted to check before I try to fix it. I also have 4 holes on the cavitation plate from a prop guard which was removed at some point.



What should I do in the way of prepping the area? Is it advisable to disassemble the lower end for this or can use a backer for the hole and then epoxy?

Any suggestions for prepping and painting once the holes are filled?
I guess I'm also looking for a shop manual for this too, what is a reasonable price or good place to find one?

Thank you
Richard

 

You know, where there're no holes the castings might be eaten away inside.
Would it be too depressing to tell you to forget that engine?

 

Marine-Tex!

http://www.marinetex.com/marinetexepoxyputty.html

I've used it on a refrigeration plate that was broken open and it held indefinitely over the years, through hundreds and hundreds of freeze/thaw cycles on the cold plate.

It could surely hold on your OB.

 

It was a freebie so no, not to depressing. I would like to get it to a usable state if possible... just as a fresh water trolling motor, nothing else.

 

I just noticed you asked prepping and priming questions:

*Drop the lower unit and be careful not to get anything from the job inside.
*Sand off the blue paint a way back from the hole
*See if you can get something to support the epoxy, although it's a paste and self-supports for the most part
*Apply Marine-Tex for metal
*Sand Marine-Tex smooth to create even surface with rest of lower unit
*Apply an aluminum "self etching" primer paint
*Try to match the color of the original paint

Done!

 

If you've got nothing into it, I suppose you could spend a little for some epoxy. Looks like salt water and constant at that. The problem with corroded old stuff like that is that they tend to have other problems as well. Every internal cavity will be somewhat eaten away. Bolts won't come off easily. Removing sections and parts may prove nearly impossible.
Good luck in any case. Report back after you get it running----- if you manage to do so!

 

I concur with Alan White.
Salt and the light alloy have built complex compounds in the threaded holes that take up space where there is none, gripping the stainless bolts with incredible force. If a head snaps off, you're done.

Call the Honda "Old Wetfoot" and put it in your garden.