[Bushwacker]

Shana, you're wise to ask about the CG shift with various powerplants! Connor is right, in that a bracketed outboard will shift the CG aft unless the outboard is a LOT lighter than your current sterndrive configuration, which probably has the majority of it's weight forward of the transom. If you go with a bracketed outboard, I'd pick the smallest setback you can live with along with the lightest motor. A big flotation tank helps keep the scuppers higher at rest, but it's irrelevant when you're up on plane since the tank then has no effect on CG.

Not sure this is true for the 25 Seafari since it was not built as designed (with the ballast tank), but Moesly located the fuel tank right on the CG for all of his designs so they wouldn't change trim as fuel was burned off. (He was a veteran military transport pilot, and pilots understand the impact of CG on vehicle performance better than anyone else!) If you assume the CG of your current configuration is located at the center of the fuel tanks, it's pretty easy to calculate how much the CG would shift (in %) from it's current configuration with a given powerplant. . .

First calculate the total moment about the CG (weight x distance from CG) of your B/M powerplant: Moment (B/M) = (total engine wt x distance from center of engine to ctr. of fuel tank) + (total outdrive wt. x distance from transom to ctr of tank) = XXX lbs-ft.

Then do the same for the outboard: Moment (OB) = (Motor weight x (distance from transom to tank ctr + bracket setback distance)) = YYY lbs-ft.

If the YYY number is 10% larger than XXX, then the CG would shift aft by roughly 10%, etc. If you know everything but the outboard weight, you could set the 2 equations equal to each other and solve for the weight of the outboard needed to avoid a CG change for a given bracket setback! (They're typically 30") Denny