Hi i have a 1989 pachanga 27 with a newer 502 carberated motor in it, not really sure what i should be turning for Rpms in it. I have a 21 pitch bravo 3 blade that 5100 to 5300 which I felt was to many Rpms, and i have on it right now a 24 balastic 3 blade that was turning 4500 to 4600 rpms the other day. I would like to jump up to a 4 blade or 5 blade but not sure what pitch would be most efficient

502 mag from mercury revs to 5050. 4600 is wayyy to low and will wear it out by lugging it.

502 mag is rated 4600-5000rpms at WOT and running slightly above is that is fine.

If your engine has a cam that is larger than stock, then running closer to 5200-5400 rpms is where ti should be.

My tac could also be off seeing the boats pushing 30 yr old and the gauges are original. haven't had a problem coming out of the hole with it on the 24 pitch prop, and the water conditions haven't been the greatest with a lot of current.