hotjava66

Just curious how a Bravo will handle RPM's and if there is an upper limit where damage or accelerated wear occurs? Did a quick search and did not come up with much. Kicking around a couple ideas but do not want to damage drives in the process. Also curious about the benefits/effects of extra rpm at the prop shaft. Is it desirable to spin a smaller or equal prop faster or gear down to run a larger prop at the same rpm? Seems like there would be less loading on the gears in the lower with a smaller prop spinning faster? Any disadvantages for the prop hydro dynamically to spin faster?

smiklos@sunprint

iTrader: (1)

We ran 372 CI small blocks at 7200-7600 RPM with non XR drives in the mid 90's almost no wear or failures. You need a big drive lube reservoir and over fill them.

Steve

hotjava66

Ok, that's way higher than I was thinking. 6000-maybe 6500 tops for what I looking to do.

Bilgerat

I would think the overall torque load would be what you need to think about. Small blocks as in the Saber we used to run, were spinning 6000 with stock gears, as well, no issues. And I know lots of guys with big blocks at that RPM. I was also always under the impression you wanted to run as much gear as possible ( geared low for example 1.65 preferred over 1.5) unless the props do something funny with the boat. I have experienced big pitch props that kind of "Paddlewheel" the back end of the boat around.

Bilgerat

just noticed you have a Saber, The Saber I mentioned belongs to Brad, "Team Kansas".

hotjava66

Yes, I am thinking about switching to small blocks. Would probably twist them 6-6.5k RPM. Got some info from Brad a while back and kind of figured they were running 1.65 drives based on the numbers he is getting. When you owned it did you ever try 1.5 drives? Just curious, would add a whole new level of cost if I needed to switch gears. Adds a whole new level of trial and error, would like to pick up more cruise but only way to do that is to up pitch and not sure if I could up a size and spin them an extra 1k RPM with the power I am considering.

BenPerfected

We raced 1.5 ratio Bravos with low compression 500 CI BB with 750-780 HP that were set to run at 6800 RPM....similar design to Super Cat engines. Never broke or even showed any wear with Max Machine Bravos. If your max torque is less than 700 lbs.,I doubt you will break a drive with a twin engine 28' boat. However, if you have a single engine boat you might have issues. Getting on plane in the 3000 RPM range is the danger zone.