Where I bought my rebuilt motor for my 170 there was a 170 in the storage lot and I asked the shop owner about it while I was hanging out. The boat had a closed in transom and a bracket on the back with a 150 4 stroke (if I remember right) on it. The guy said the owner of the boat, a buddy of his, wouldn't listen to him that the bracket added the weight too far back, like cc86 just mentioned, and he went forward with the rebuilt anyway. Looked real nice.On his maiden voyage he came off plane real quickly and the boat sank from the backwash - all in the first 10 minutes of the voyage.