Change damper plate with boat in water?

You wouldn't be the first one to do it

I'd start with disconnecting the coupling and sliding the shaft as far back as it will go and check the packing leakage at that point.

If it's normal, you shouldn't have any problem doing the rest of the job in the water.

Disconnect water lines, exhaust hoses etc at the highest point above the water so no water can leak in when you're jacking up the back of the engine. With a 1.23 to 1 transmission you shouldn't have to jack it much.

I'd make sure I had the right wrenches to tighten down the packing gland if it started leaking a bunch suddenly in the middle of the job.

Keep in mind that if you grunt down on the packing, it most likely won't loosen up up again when you back of the nuts later and you may have to repack the shaft, but if you never have to tighten it during the job you'll be fine.

Also keep in mind that "I ain't the smartest guy in the world" ............but I helped a friend swap his transmission in the water and we didn't get wet.

Mikewolf wrote: Thanks for the tips. Are there any “while you’re in there” job I should get parts for?

Some people will tell you to replace the rear main seal on the engine and the front seal on the transmission while things are apart.

Others will say "if it ain't leaking, don't touch it"

Whatever you do, it will invariably be the wrong thing"

But you can look for signs of leakage to help you decide

What symptoms are you having that made you steer to the damper plate being the issue?

Reason I ask..

I have a small vibration around 1200 rpm. Ive had my prop balanced, checked shaft run out, changed plugs, disctributor cap, the works. Only thing I did not do was align the prop shaft coupling in the water. I did that on my trailer, so i need to recheck that. I need to dive in like you to change my rear main seal and am going to change the damper out at the same time while im in there.. hoping maybe that will help my vibration