A friend recently showed me his drive extension and said that he thought Mercruiser made a 3" plate that went between the transom and the drive housing. He thought that you could still use the tiller steering. Anybody know about such a devise??

What your describing sounds like a Stern Jack made by Land and Sea.

With the Land and Sea Stern Jack you 're going to put more strain on your gimbal ring of which should be upgraded to the Heavy Duty one of which you then can't use your stock trim sender and limit switches I believe.

Well I did it. I bought a stern jack, a used one. I installed it on this heavy boat 9,000# + and I am going 3-4 MPH faster @ Tahoe (6200MSL). My next test will be @ sea level. Hole power has significantly improved. More after the next test.

no **** that's great I was contemplating going with an Imco ext. box