Transom Bracket Mounting Height

[ApolloHT]

Strick,

Thanks for the info. My extensive internet research has led me to one of the sites already, but the two stainless sites are new, and appreciated.

Let me put this same question to you a different way. If the rule of thumb 1" per foot is accurate for installing a transom bracket, and measuring the setback distance as you described, wouldn't it be safe to assume...if I had a 13 degree transom, and the water flowing past the keel would in actuallity be more then the measured setback distance (because the of the angle of the transom, and the keel being further from the point of the motor mount) and thus, you would end up with a transom bracket which would be installed in a "safe" position (safe meaning...you would never have to go lower), and the only adjustment of the motor would be up? I hope you followed that way of thinking. Another way to look at it...the top of the transom bracket mounts to the transom above the keel...and with a 13 degree transom, this would mean the point at which the water is flowing past the transom is acutally a few inches further forward.

One other question...according to the specs, a 30" shaft Suzuki DF250 (weighs 591lbs) is only 11 lbs. more then a 25" shaft. So why should I be any more concerned about the size of the flotation bracket, then if I was using a 25" motor. In addition, I would think a 36" setback bracket would add even more flotation then a 30"...but then...it is an additional 6" further back...so I could be way off base.

Like you said...I want to do it right the first time, because having to redo it...is almost not an option. Bear with all my silly questions, it is good for me to bounce these theories off someone.
Thanks,
John

[strick]

I think I see were you are hung up. The 30 inch setback measurement is taken from where the motor mounts to the bracket in a straight line to where the top of the bracket touches the transom. Dont worry about the 13 degree angle causing the bottom of the keel to be farther forward. As I said before on notched transom boats the cavitation plate is usually level with the bottom of the keel.... on bracketed boats the cavitation plate should be about 1 inch higher then the keel for every foot of setback.. Thus a 30 inch setback bracket would place the cavitation plate about 2.5 inches higher then the keel. If you are worried about having to lower the engine and destroying your bracket then just mount the bracket 1 inch lower then you had planned. On the boat I have now I have the anticavitation plate almost 3.5 inches above the keel and the boat runs great.. no cavitating what so ever so there is some room for error.

My comment about building as big a flotation chamber as possible had nothing to do with the difference in the length of the shafts of the two motors....my point was mearely that you have a big heavy motor and the more flotation you provide for the motor the nicer the boat will set in the water. Huage trim tabs may or may not get in the way of the bracket...D&D marine used to have a great installation page with diagrams for there brackets but they have since limited access to the page.

Strick