Shaft length

Hello iboaters. I have a question I and I feel sure you can help. How do you determine shaft length, is there a formula or rule of thumb? I am changing a very old Mercury Thruster Plus for a New Minkota Edge. I just bought the new Minkota and after I brought it home I discovered there is a great difference in shaft length; 45" on the new Minkota vs 33" on the Thruster Plus. Both are foot operated, the Thruster is about 26 lbs. of thrust and the Minkota is 40 lbs. What problems will I be looking at and how can I resolve them. The boat is one of the heavy old glass Bass boats, 16 ft. (1972) I really want to keep the new one but I haven't even opened the box. Sorry if this is a bit wordy but I have to say thanks for helping me many times keep my old boat running by doing searches on these forums or with knowledge I gained just reading these threads for entertainment. ..........Draghoe

Re: Shaft length

You measure from the surface on which the troller will be mounted, to the water line, then add one foot. Too long is not a problem as you can adjust the height. The problem arises when the shaft is too short as waves may pop the prop out of the water. Of course way too long will be a problem if you fish close to shore as the motor would strike underwater objects more often. But as I mentioned, the motor can be adjusted upward. You just end up with the head sticking up rather high. There will be no problem with operation with the longer shaft.

Re: Shaft length

Thanks Vice Admiral. You made my Day