maxium rpms

[rockyman]

1978 inline 6cyl 250 chevy 165 merc outdrive installed in 1981 19.5 galaxy , i normally run motor between 38 to 42 rpms, and it plains off pretty good at that speed but i still have a good 1/3 of my throttle left .what would be the maxium rpms i should run motor on long runs up and down river.i have a 19 pitch prop on outdrive

 

[Don S]

Re: maxium rpms

WOT rpm should be between 3900 and 4300 rpm with normal load.
If you go above that in rpm, that just means you are under propped and wasting your rpm. If you get your maximum WOT rpm at normal load and properly trimmed, then (by posting in the prop forum) you can find out what prop you should actually be running. But you do need to know you present WOT rpm.

 

[rockyman]

Re: maxium rpms

dont mean ask a silly question but what does wot mean

 

[Don S]

Re: maxium rpms

Sorry bout that. Wide Open Throttle.

 

[JustJason]

Re: maxium rpms

Basically your maximum RPMs with the throttle lever all the way down.

 

[turborich]

Re: maxium rpms

I have that same engine & my RPM's top out at 4,000 RPM's. I am sure that I could change props to reach the upper 4,300 if I wanted. I'm sure that you could change props as well to correct this if it's a big issue to you. If not just don't go over the 4,300 RPM's. You don't want to hurt your engine by spinning it too fast.

 

[MikDee]

Re: maxium rpms

1978 inline 6cyl 250 chevy 165 merc outdrive installed in 1981 19.5 galaxy , i normally run motor between 38 to 42 rpms, and it plains off pretty good at that speed but i still have a good 1/3 of my throttle left .what would be the maxium rpms i should run motor on long runs up and down river.i have a 19 pitch prop on outdrive

As long as you can confirm your prop, or coupler is good, so that you don't overrev and burn out your engine out, you should open it up, and check your WOT rpm's. I don't think it can be that much more rpm's with that combo. Then prop up (more pitch) till you reach 4300rpm max at WOT, figure approx. a 200 rpm drop for each 1" of more pitch, but you'll also loose some hole shot.