I have an been out of RC for some. I am cluless on the brushless motors. I am getting an old boat out of the closet and want to update it to Lipo and brushless. It is an old MRP(?) 41" Fountain Superboat. I had originally powered it with twin Trinity 427's (16 double?) motors running on 20 1800 cells. It ran ok but the runtime was short. I now want to go to single brushless and lipo's. Any suggestions?

Not sure what kind of driveline you have, and also what type of cooling system it has.

But, I've been running the new Aquacraft SV-27 and UL-1 boats. They have brushless motors, and ESC's. I run these with 2 - 2S 5000mah Lipo batteries in series (4S)

I just upgraded the SV-27 by putting in an Electrifly Ammo 36-50-2300Kv Brushless Inrunner Motor, and upgrading to the Aquacraft 60-Amp Marine ESC LiPo Ready.

If you send me some pics of the inside, I might be able to assist you further.

Big thing is cooling. I found that out the hard way... the stock water jacket didnt keep up with the new motor.