Hi Mudhen,
There is a sticky on brackets that you should read. Although I have a bracket on a 23 sf, I have mixed feelings regarding the benefits. It creates extra room inside the boat and gives you a great swim platform, but will shift your CG back. Hard to see what size motors you have, but you would be moving up to 1,000 lbs 30" back, creating about 2,500 ft-lbs of extra moment, shifting your center of gravity back about 0.5 ft. It may lead to porpoising, handling issues and a higher minimum planing speed. You will probably have to shift some weight forward to compensate. Moving 200 lbs of batteries from the stern to under the console would only give you about half of what you need. You will likely need trim tabs if you don't already have them.
The previous owner of my sf had a pair of 200 hp ox66's on the bracket (I think it is a Stainless Marine). Even with batteries under the console and the installation of k-plane 280 trim tabs, they ended up using water ballast in the forward fish locker to alleviate the imbalance. The boat actually sunk at the dock under similar circumstances to yours. I believe that the scuppers were the culprits because when I got the boat (minus engines and electronics) the thru hulls were glassed in and the scupper drains just routed to the bilge where there are two large pumps. I personally like this arrangement as there too many situations when there is too much weight in the back, leading to back-flow into the boat. As well, the hose or tubing may fail and water will flow into the boat if the thru-hulls are submerged. If I were to lead my scuppers to thru-hulls, I would definitely have ball valves on the thru-hulls, and close them when I am not on the boat or experiencing back-flow.
The current arrangement I have is a single ox66 250hp and a 9.9 kicker mounted on the twin bracket. While the weight balance is not as bad, I still think the boat is ass heavy. I use my trim tabs most of the time, especially when it is rough, because no-one wants to sit in the front as ballast. While the motor is at the perfect height at regular cruising speed (cav plate is 4.5" above keel), the stern tends to squat at minimal planing speeds even with the tabs down. Having the motor 30" from the transom means that the water has a lot further to travel before it hits the prop. I think a rises more than if you have the motors mounted on the transom, leading to more situations where the prop is too low in the water with the cavitation plate submerged, which creates more drag. I can trim the motor up and the tabs down, but this is less than ideal.
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