Re: leaking water in boat
First off there are 2 sizes of transom boots, get the right one. Know your boat year and model.
The boot is not a hard job. You DO NOT need to remove the drive. unscrew all the screws and pry out the aluminum ring (I would mark the top as some rings aren't marked very well), then using a scraper, razor blade or similar thing scrape the boot loose. Inside you will find a giant hose clamp that holds it to the drive. Loosen the clamp and the boot is ready to be taken off. For ease of removal just cut it on one side to get it off.
Clean the transom of all the sealer and finish cleaning with carb spray or solvent to provide a clean surface for the new sealer to adhere to.
Noting the 3 arrows as UP you will have to stretch the new boot over the drive being careful not to cut or tear it. Once over the drive center the boot and make sure it is seated in the groove around the drive (clean this too). Replace the clamp making sure the boot and clamp stay in the grooves they are supposed to be in, tighten the clamp, first giving it a little shot of something to lube the screw so it doesn't gall.
Now recheck the boot for alignment. If good, place the ring back in the groove around the boot (also has top and bottom). Now it is time for the sealer. Life Seal is one of the best to use. But any quality (because you don't want leaks here) sealer designated for Below Water Line will work.
It will help when re screwing to use an awl or two to help align the holes and hold it while re-screwing (through the boot in to screw holes). If you have any stripped holes, go one size larger with the screws (from 8 to 10) or try a piece of wood strip in the hole to shim it up. Any screws larger than #10 will require slight drilling of the hole in the alum. ring.Make sure you put enough sealer so it will ooze out and you can run your finger around the outside to bead it in place.
Allow over nite or as required by product before returning to the water.
I can do this in 45 min. But then I have done dozens of them. Give your self 2 hours for the job.
While you have the boot off it is a good time to check your tilt motor for tightness, as well as all the little things you can only see with the boot off like for transom rot, The rear of your stringers for rot, loose wires, etc.
Good luck!