I'm building a 540 for a 22' classic donzi probably 475 to 530 hp. the engine is all motor no blower so I'm concerned about how much can the drive handle? 1.5 ratio drive

I can tell you that it can't handle 650 for sure. George at AAD showed me what he does to improve the Bravo's and when you look at the bearings, it's downright scary. I'm surprised mine lasted as long as it did, probably due to the Amsoil I was running. I hate to say this but, your drive will fail and most likely it will be due to a bearing failure followed by the top vertical shaft breaking. George has a whole box of broken parts he can show you. Fortunately for you your boat is light so you can get some miles out of it. I recommend checking the bearings in the top at least every other season. It will save you from sitting out on the water for 4 hours waiting for a tow at $625.

Check out All American Drive (AAD), they build up B1 drives or consider installing an XR? Either way, HP = Broken Bravos

I can tell you what it can't... 620HP

A 22ft will make it last longer, but most will agree an XR should be the minimum.

Sorry for sticking my nose in, but if wanting 475-530hp why not stay with a 502 ?

It would take a few potatoes in each tailpipe to make that hp with a 540...if you know what I mean ?
ie: reduce effeciency big time to keep the power down.

think you would be surprised how long a bravo 1 would hold up with 500hp on a fairly lightweight 22 donzi. i know people going on 600 hours behind 502's in a 33 outlaw (significantly longer and heavier boat). river running and ocean running. everyone will agree bravo is crap but again i think youd be shocked how long they go. my guess is 150-200 hours with gentle use.

I'd venture to say it has more to do with your driving style and the boat its bolted to than strictly HP..

a Bravo on a sweet 16 ran on a river or small inland lake would last much longer than the same drive on a heavy cig or Formula running hard in a 5' chop in the Great lakes.

A properly assembled B1 with the right parts and driven with respect should hold up to your power level with no problems. But on the other hand, anything Bravo can be broken if try hard enough. Just my $.02.
What year is your drive? Newer thick floor upper gears installed? What does the serial number on the drive start with? OM or newer has the thick floored gears.

Hope that helps.
Dick