I Have a 33 Fountain Executioner Speed master 2's and Borg warner 1 : 1 transmission's (velvet drive i think ?) I'm wondering how much HP they can take with sensible driving. I never slam the throttles at hole shot only once up to 30+mph. Most will be offshore at cruise speed with a squirt here and there at WOT. I can restrain WOT to flats if I have to.

I have run 450 hp 502's through them for 6 years all good, I always thought they were bulletproof and gave them a fair bit of In & out of the water at speed !!

The strengh of the drive's will be a big factor in rebuilding my 502's to approx 500-550hp or stroke them to 540's with approx 550-600hp max.

Also the borg warner transmissions , how much hp can they handle? Ive heard about putting an extra clutch pack in ?

Thanks for all your info, cant find many threads on Speedmaster 2's

You will be good at 500-550 with a 502. The 540 will make more torque but still would be ok at the 600HP mark. I would make sure all your shimming in the upper and lower is good. Randy at Cobra has some gears laying around for the #2 stuff some spares stress relieved and coated would not be a bad idea to have on the shelf.