How to replace Mercruiser lower transom mount bolts?

[landingzone]

I have a 1988 270 Amberjack with twin 4.3L Mercruiser Alpha I outdrives. The lower bolts which attach the outdrive to the transom are severely corroded. They have not yet caused any leakage, etc. problem. I know that they are aluminum and should have anodes at there outer ends (which are long gone).
My question is to determine if I have to remove the engines to replace these. I saw a post on some forum that indicated that. I also talked to a marine mechanic who suggested that by removing the exhaust manifolds from the center area, I might be able to access and remove/replace the bolts. Has anyone replaced these without removing the engines and if so, please enlighten me. Thanks

 

[Her Diamond 2]

I had a transom leak on my 89 250 Sundancer and the marina pulled the motor and replaced the transom seal and bolts. I've never heard of any other way.

 

[dev6315]

I can tell you from experience, the only way is pull the engine. The exhaust Y pipe wont allow you to replace while installed. Its a good winter project, perfect time to make the bilge look great.

 

[landingzone]

So "dev", are you saying that there is no room between the Y pipe and the transom to get at the nuts, or the Y pipe blocks any access? It looks like if I removed the 2 inside manifolds I could reach the lower Y pipe area but it sounds like that might not give necessary access. All assembled, there is no way I can even see the nuts.

 

[dev6315]

I have a huge engine room for a boat my size. I was able to lay on my side with a mirror and flashlight and still couldn't access the bolts. I do know there are two nuts, not sure if they are the lowest ones you want to replace, but there are two that are totally blocked by the exhaust Ypipe. Thats when I cut my losses and pulled the engine. Honestly, I know its intimidating to think about, but its not that bad to pull. Label everything, take pictures and mark shift cables to get back to an approx setting. The drive will also need pulled, but again, this is a prime time to do maintenance without having to be a Russian gymnast.

 

[landingzone]

Thanks for the help!