TOPIC: Transom through bolts

This one was quite a supprise. I noticed the top right engine flange had pulled back from the transom about 3/8 of an inch. When I tried to tighten the top right bolt, with no effort at all, the bolt broke in to. This was a factory instalation, in 1964.
The transom is sound. They used some kind of aluminum alloy bolts and electrolisus(?) ate them up.
These bolts were holding a 90hp Johnson V-4 on a Glasspar Super G.
I guess we had better take closer looks at those old "factory" installs.

These were the transom through bolts that held a 1962 70hp Merc on to a 1961 g3. Also original, Mike

Holy cow that's scarey! Between the fact that obviously many installing dealers didn't bed/seal these bolts very well (or at all!) causing water intrusion into the transom, and what you have discovered, I'd say this should be high on the checklist before any Glassic is returned to service, or even trailered for that matter.

I was planning on pulling mine this weekend to check the wood in the transom, but probably after going out on Saturday. UPDATE - That baby isn't going anywhere until she's checked out, I'm still running the original install bolts untouched!

Thanks for sharing this guys, a good "heads up".

Update #2 - Bolts good, transom bad.

yeah when we pulled the motor mount bolts on the transom of the suray,they broke off,the bolts were aluminum and the nuts were steel,it made a chemical reaction,and the nuts would not budge,we have gotten stainless bolts and nuts for the install,john

Stainless steel would be the best. Contrary to popular belief, aluminum does oxidize. Ever see alloy wheels on cars in Minnesota? If the plastic coating gets nicked, the corrosion begins.

Thanks for posting that. I would not have considered that would ever be a problem.

Important safety tip.

The thing that got me the most, was the top bolts were the worst. The bolts, nuts, and the washers were all of the same type of alloy.
If you look close at the picture you can see that the front lip of engine mount is keeping the engine from going back any farther. The top right bolt didn't break it was oxidized all the way through. If that engine had been mounted up off the transom 1/2" or more?
They have been replaced with stainless and sealed.
Darb