What Engine size?

[Fr. Frank]

I posted this info in a different forum, but the USCG (not the mfg) recommended max HP rating of a 20MA is 230 hp. Add a swim platform and it jumps to 250 hp.

The formula for a single engine is (LxWx2)-90= max recommended HP. Max HP is always rounded up to next higher 5 hp increment.
Length is LOA, (including permanently mounted fixtures or accessories) rounded up to the next higher foot. Width is beam at widest point, rounded up to the next highest foot.

If your transom is 30" or if you have a bracket behind a closed transom, the multiplier for single engines is 2.5 instead of 2.

If you have twin engines, the formula is (LxWx3)-50= max HP. This is why the early Potter-era 23'3" Seacraft CC twin OB hull had a max HP rating of 500 hp, later reduced to 400. The new 23's are mfg rated for 300 hp max

So with a bracket