Ha McGillicuddy
Tab size science is more like a art that a mathematical formula. There are a number of factors that are considered like weight on the transom – one or two outboards, dead rise, or possibly a single inboard on a jack shaft – center of the boat. Weight distribution and that type of stuff. I have a pair of 12x12 on the back of mine and they work just great with a single outboard. The M120 are 10x12 with a down fin which holds the water under the tab longer with out letting it escape out the sides would also work good. If you look at the new 23 Seacrafts none of them have 18x9 most have from a 12x9 to 12x12 on the back. I would say that if you had a I/O and lots of weight at the stern plus are having lots of trouble getting up on a plain then you might need a bigger tab.
As for need of tabs if you look at most boats coming out of the manufacturers plants now a days most boat builders have them as standard equipment.
Good luck.
FellowShip
Just for the Grins
