Re: transmission question
If you are going to use it to power a boat, you should ditch the tranny and fab a coupler that bolts to the flywheel. You will get no benefit from having the transmission, as that little 2.5 horse motor would not have the torque to turn a prop in the manner I am envisioning that you are talking about. You are looking at 120-ish horsepower there, best just couple directly. What is your final drive? An inboard configuration, an inboard/outdrive, or a V drive?