I pulled my YSM 12 from my Mariner 28 using an old main sheet tackle and a 4x4. Once the engine was in the cockpit, we hooked it to the boom and lowered it over the sides. I should have padded the boat with old blankets, and drained ALL the oil and trans fluid. Only down side was a couple of small gel coat chips and an oil stained main sheet. Usually the engine must be mounted on an angle to match the prop shaft. Make sure you have enough room above the angled engine. The additional HP may require a new prop and/or prop shaft. Also check that exhaust and cooling water through hulls are on the same side, to avoid a lot of additional work. Check weight, and make sure any additional weight will work in your favor. MY ysm was 320 lbs. I looked at a couple of 3 cyl that were 500+. If the attractive part of the new motor is price, figure very carefully. Adjusting the sub systems can be expensive. Pulling the 2gm, having it rebuilt and reinstalling is likely cheaper and easier that an engine swap. In my youth we used to say that with enough money and a big enough hammer you can put in any engine you want. Double that for a boat!