[Blue_Heron]

I haven't had my 25 in the water yet, so I'm just drawing conclusions from the information shared by other Seafari Owners. But this hull is supposed to be a little tail heavy, and maybe a little top heavy. That's why Mr. Moesly designed the ballast tank system for it.

Stern drives are heavier than outboards, but their center of gravity is located forward of the transom and below the waterline. Outboards are lighter, but their center of gravity is behind the transom and above the waterline. Put them on a bracket, and their CG is WAY behind the transom. That just seems like the wrong way to go with the weight distribution for this hull.

I did a little math to see what effect different engine configurations might have. I had to make a few assumptions, some of them just WAGs, but here they are:

* The CG of the 25 is 8' forward of the transom heel, per Bigfluke
* The CG of bracketed outboards is about 40" aft of the transom (30" for bracket, engine CG 10" aft of that)
* The CG of a V-8 I/O is about 16" forward of the transom.

A Yami F250 weighs 562lbs. Multiply that by a moment arm of 11.33', and you've got an aft pitching moment of 6369 ft lbs.

A Mercruiser 350 Mag MPI/Bravo 1 weighs 1044lbs. Multiply that by 6.67' and your pitching moment is 6963 ft lbs., about 10% more than the single F250.

But stick a pair of 150 Etecs on a bracket and you've got 866lbs x 11.33' = 9811 ft lbs. That's 54% more pitching moment than a single F250, and 40% more than the I/O.

If my miscalculations are anywhere near correct, a single outboard, even a big one, won't be a bad thing for longitudinal balance, but even a relatively light pair of twins is going to throw the balance in the wrong direction.

It seems obvious that switching from I/O to outboards will raise the cg. I won't even attempt to calculate how much, or what effect it might have on roll characteristics, but it seems to me that a deep V hull with a very narrow beam is going to be a lot more stable in the roll axis if the cg is as low as possible. Switching from I/Os to outboards takes the vertical cg in the wrong direction.

My $0.02
Dave

P.S. Denny must have entered his post at about the same time I started writing mine. Same principal, I did some guessing on the math.