Gimbal Housing to Inner Transom Bolts and Studs Replacement??

[76SeaRay]

This is an Alpha One Gen One. At the very top of the housing, there are two bolts that look in great shape (almost new looking). Next going down the drive are the two long studs that look in good shape with some corrosion on the tips of them on the drive side of the gimbal housing. The ends that go through the transom and inner transom plate seem to just have very light surface corrosion. Continuing top to bottom, the next two bolts with the square washers are severely corroded away to about half their thickness (surprised the came out without breaking). Finally, at the bottom are the two "zinc" bolts and they appear in good shape as well.

My question is, should I pull the studs out and replace them since the two bolts right below are so corroded? I don't know why the two bolts with the square washers are so corroded compared to the others. I can only guess that the top and bottom bolts were replaced at some point in time but not the corroded bolts. I am just concerned with the studs and whether they are heavily corroded inside the threaded hole since they appear to be originals and should be changed now. I haven't attempted to take them out (let sleeping dogs lie???)...yet....

 

[Rick Stephens]

If you have the gimbal housing out where you can replace them, I sure wouldn't leave corroded studs in there before reassembly. When you pull them, use heat from the side on the shafts to expand them in the gimbal housing and break loose any corrosion. Then before they cool all the way turn them out with a pair of nuts locked together. You need them still hot in case there is thread locker.

 

[tank1949]

I assume you have pulled motor? MC has changed transom assembly designs over the years. My Bravos have 8 studs and no stud has anodes on the outside of gimbal housing to be exposed to water. I have learned the hard way to never store an aluminum OD in salt water. Is yours moored in salt water? I had to heat my studs to remove them in preperation of transom replacement. I suspect your alpha is at least 20 years old. Maybe someone else has information on square washer. I replaced all my washers with stainless because I had a lot of SS. I used a jam nut on the back side of a regular nut to remove mine from gimbal housing, after heat. Then rethreaded with tap to clean out old crap. I believe manuals calls for red locktite when installing new studs. I also suspect you have some water intrusion and may need to replace transom. Corrosion is coming from water and from somewhere. Yeah, it sucks! Just pound hull around transom hole. You will find rot or not.

Rot usually creeps from drain hole upwards. If you have any, you should be able to find it. ​

Buy all new bolts to replace corroded ones. I believe bottom 4 bolts are 1/4" shorter. You may have model OD that the LAST TWO BOLTS HAVE ZINKS AND ARE ALUMINUM or zinc. I don't agree with this type MC design and apparently they didn't either later on. There are enough zincs on the OD. Replacing these bolts with motor in boat is a pain in the a., so do it now. God luck!

 

[76SeaRay]

I guess I will give it a try to get them out with a bit of heat and jam nuts. tank1949, I have the boat completely disassembled for complete restoration and the transom has already been replaced.. Working on restoration of the engine bay "stringer box" and the all the sterndrive parts.. The sterndrive came from a donor boat so I don't have a history on the gimbal/transom plate mounting bolts or studs.

I have been trying to find the right part numbers for replacement parts but getting a bit lost in all the different versions. The parts diagrams I see online show 4 or 6 studs. So, for mine, should the top two be studs instead of bolts, next two are studs already which seems consistent, but should the next two down be studs instead of bolts also? There is also a note about "new design" in the parts diagrams but doesn't specify what the difference is for the bolts or studs.

 

[Rick Stephens]

I recently did the same thing. I used the donor transom serial number to determine my parts. And like you, I replaced all my studs and bolts.

Use jam nuts and Vise-grips at the same time to pull the studs. More grip the better to keep from breaking one.

Rick

 

[tank1949]

You didn't say if v8/6 or inline motor. If a V motor, you will also have a Y Pipe that will bolt to gimbal housing. . The slightly shorter bolts will allow pipe to fit. You should also check pipe for corrosion. Salt water eats them up and they cannot be easily replaced with motor in boat.

 

[rad1026]

"I have the boat completely disassembled for complete restoration and the transom has already been replaced" Glad to hear this. I was going to respond yesterday but I didn't want to be the bad news guy. When you said stud corrosion I though you probably needed a new transom. Hope the restoration is going well.

 

[76SeaRay]

This was an old OMC stringer drive so that required a transom change plus it had rot along the bottom. Probably could have replaced only the top half but bit the bullet and did the whole transom (high free-board on this cruising boat) and that way I had solid clean transom to work with... The old transom was only about 1 1/2 inches and not flat so that drove the decision as well.. It is a 5.7L V8 Vortec newly built up so it does have the bull horns (4 bolt pattern).. Looks like those bolts could be a pain to reach and I am assuming I need to put them on right after the inner transom plate so I have room to get at them... It also looks like I need to trim a bit more around the opening where the bull horns go against the gimbal housing...

Anyway, back to a question, should I use bolts in the top two, studs in the next row, bolts in the next row with the square washers and finally stock zinc attaching bolts on the bottom or should I replace the top six bolts with new studs..??? I have stainless bolts for the bull horns...

Thanks...