I am new to boat ownership and all the maintenance that goes with it. I recently picked up a 1985 23' Imperial with a 170 Mercruiser engine and a 3.7l Mercruiser outdrive. When I bought the boat I was told that either the engine or the outdrive was locked up. I thought for $500 it would be a good project boat. After doing some research I found that the outdrive was the problem. After pulling the outdrive the engine would crank over. Come to find out the bellows had failed and that is where the problem started. I seperated the upper from the lower and the lower was fine, but the upper was locked up. I took the top cover off and found the problem. The bearing and the bearing housing was completely blown apart. Now for my question, can I take a 3.0l Mercruiser upper and put it on a 3.7l lower. Any other additional information would be much appreciated.