Building up transom question

I currently have two boats, a 14 foot trihull fiberglass with an older 70's long shaft Evinrude 60 on it and a 17 foot aluminum with a short shaft 35. I plan on getting rid of the fiberglass one and want to switch the larger motor over to the aluminum, for the increase in power but also the controls are in better shape as well. Problem is, somebody in the past had cut down the transom on the aluminum to fit the short shaft 35 to it, so now I would have to reverse engineer that to fit the 60 on it. Is this something that can be done as a DIY or should I just have the local boat shop do it, not really sure how much $$$ that would be though.

 

Besides making the aluminum taller for the long shaft cutout, you'll probably need to make the transom thicker too. The difference between a 35 and 60 means you should go from 1.5" (38 mm) which is what it probably is now and make it 2" (51 mm). There also may be a need for some longitudinal bracing (knees) too. Can you post a picture of the inside of the transom area?

 

At the moment, the boats are stored at a friends place, out of town...will take some pics as soon I get the chance. I can't recall, but I imagine the transom of the aluminum was probably thicker originally, for a 17 foot would be rated for more than a 35 I imagine, but will see as soon as I can get up to drag the boat back down to the house. The info plate is long since gone off of it, I recall trying to find it last year to find out a HP rating, with no luck.

 

Bigger motor be hard on fuel with a lighter boat?

Discussing this project with my wife and she had asked me if putting the bigger motor on the aluminum boat would result in better gas mileage than the current 35 or not. I wasn't really sure, bigger motor consumes more fuel, but if its now on a much lighter craft, maybe it won't have to work as hard?
Been basically talking of the pros and cons of this outboard switch between boats..
I was originally planning on just bringing in the aluminum setup into my marine shop and having them tune it up and look at the sloppy controls on it and see if that could be fixed up. That is what got me thinking of just using the other boat and set of controls, for the controls on it are nice...but a heck of a lot more work involved! lol

Have a question about getting new controls for the aluminum, but will start new thread for that one.

 

Unless you are a speed demon, leave the 35 on the aluminum boat, sell the larger motor and use the proceeds to buy some quality control mechanisms.

The 35 will be more economical to run if you are not after blazing speed. The 35 will give you enough speed to get you where you are going with less pounding and other unpleasant side effects.