Hi I have a formula 357 with trs drives and am looking at building the engine up . I was wondering how much horsepower the B/W trans and trs drives can withstand before breaking?

That's a good question and you will probably get a lot of different answers.I never have seen Mercury state how much they will take but it seems the average opinions are about 550.I know people who run as much as 700 and have no trouble,it just depends on how you drive them.If you make full throttle starts and run them hard all the time they won't last.

I would say the 550-600 hp range should be no problem. After that your going to start twisting prop shafts and such.

you can run more than 600 hp thru the borg warners than what most have said im running cobra 1000hp motors with borg warner trannies as long as u feather them out of the hole you will not have any problems they will withstand the top end that you can throw at them 112mph is what im running on radar.

You have that 34' Scarab running 112 MPH? If so, that is impressive. Where is the prop shaft in relation to the bottom? Are the engines side by side? Any work on the bottom?