PDA

View Full Version : RPM



jthomas
06-25-2007, 03:36 PM
"I have a 1988 22' limited Chriss Craft with a cuddy cabin, It has a 350 engine that only gets about 4000 rpm. it has a 15" 17 pitch prop. and it has a cobra outdrive. IS this the wrong size prop for this boat."

dogsharks38
06-25-2007, 04:35 PM
"If it's able to get up to 4000 and not rev any further, then it appears you have the proper prop.

The SBC is designed to rev under marine load to 4000, but it's not generally good to see it rev beyond that. Sure, they'll do it, but if you are doing so, then I would think the boat is underpropped. If you are hitting the 4000 mark at wide open throttle, that appears to be the right prop.

P"

jthomas
06-26-2007, 09:13 AM
"so 4000 is the max this boat should rev. I guess i thought this boat should run faster than it does. at 4000 rpm, im only running about 35 mph. that is not exact but close,"

dogsharks38
06-26-2007, 12:23 PM
"35-mph is actually considered pretty fast by many boating standards. With high power outboards and go-fast boats, it isn't considered fast, but at 35-mph you can still break your neck on water skiis.

http://www.network54.com/Forum/424840/thread/1172181250/ ("")

Look over the link I posted for you, and you'll see a variety of SBC motors and I don't think any of them are exceeding 4200. 4000 is a good rule to stick with. By changing the prop so you can reach 4200, I don't think you're really gaining a thing.

regards, P"

jthomas
06-26-2007, 02:08 PM
thanks for the info.