chrysler 140hp help australia

hey can anyone recommend me a prop, iv now got the 140hp motor using the 85hp one piece leg/gearbox, motor is revving out to 7000rpm on a 15" standard alloy prop, changed to 21" stainless steel race prop what i used to use on my 85hp, still pulling 6800rpm, i know it shouldn't be revving that hard, but some how it dose, someone told me the mercury props fit on the chrysler spline, if need be ill change the spline, just want to drop the revs to around 4500-5000rpm so i don't burn my freshly rebuilt motor into the ground. any help would be lovely. also im chasing stacks(exhaust) for my 140hp would you know any1 that might have any, or would you know where i could get some. their so rear to get in Australia its stupid. cheers regards Shaun.

I would think the 21 pitch should be fine. My service manual (US Marine OB 3874-1) indicates a 140 HP to run 5000-5500 RPM with a 19 pitch.
Is your cavitation plate within a half inch of the bottom of the hull?
Have you checked the prop for slippage?
Maybe you should have your tachometer checked for accuracy.

borrowed a mates 27pitch clever prop today, bogged out untill around 1500-2000rpm and revved up to 4200rpm full throttle open, tomorrow after work going to try out a 22pitch clever prop hopefully have better revs, these props of my mates boats are for racing they just want their outboard to go fast. they took their boats out for a little test n tune 82mph with a mercuray 2.2ltr 200hp outboard short shaft. their pritty quick. for bullet boats.

thanks for the help/info, still working on it, gota try a few more props over easter and hopefully i find the one i require then ill buy 2