Re: H shaped Freeze crack, please help
Bad U-joints and/or gimbal bearing, and/or bad engine alignment. A whole separate project. You must remove the outdrive to check them all. I strongly, strongly recommend you refer to a service manual if you are going to try to tackle this yourself. Not difficult, but IMO too much to describe on the internet...and some tips and special tools will be needed.
I believe the service manual, and many people here, will tell you the drive should be removed and these 3 items checked and/or lubricated every year. Do you know when this maintenance was last completed? This sounds like it may be a rather neglected boat...
About the only thing you can eyeball right up front without removing the drive is a SEVERE engine alignment problem. You can predict this by looking at the engine mounts....where lag bolts screw directly into the floor of the boat to hold the engine in place. Does the fiberglass under the weight of the engine mounts appear compressed/dented/sagging? If you try to tighten the lag bolts with a wrench do they spin as though the wood they're threaded into is stripped? If yes to either, I can guarantee your engine alignment is way off, and you also have a major fiberglass/wood replacement project ahead of you because the wood structure of the boat has been rotting away. Hopefully these look OK. And let me be very clear that if they do look OK inside the engine compartment, it does NOT mean your engine alignment is also OK. Alignment can ONLY be accurately checked by removing the outdrive and then using the special alignment tool to check it.
