Max RPM

[vstol]

This almost sounds like a dumb question but i will ask anyways. My maunuals say 4400-4800 for peak rpm. With the new, slightly smaller (from b7 to b6) props i installed wide open my rpm goes up to 5000, I only did that twice, just for a few seconds to make sure it was not a fluke. Unfortunaly i really never payed attention to the wide open rpm prior to changing to props. To me it makes sense that the rpm would be a little higher with the smaller props, that does not mean i should run it like that, so should i limit the rpm to 4600 to be safe or is it ok to open it all the way up? I think limit to 4600 but thought i would ask.

 

[Laddies]

Re: Max RPM

200 RPM with the boat in a lite condtion is not likly to hurt your engine, it's usally better to be a little high than low

 

[cmyers_uk]

Re: Max RPM

If your engine is good to 4800 why limit to 4600. Id be more concerned about how long I ran at max RPM rather than what its set to. If youve got a pitch that allows your engine to overrev to say 5000 then be careful when you drive it.<br /><br />Below is some good reading about props<br /><br /> http://www.mercurymarine.com/everything_you_need_to_know_about_propellers5

 

[Don S]

Re: Max RPM

What engine are you running,EFI? you could have a rev limiter that won't allow you to go over 5000. If so, you may still be way under propped and loosing a lot of top speed.<br />You should really be in the 44 to 4800 range, if you used the B6 props, you should probably go to the B7's and see where you are. They would probably put you in the 4600 to 4700 rpm range.

 

[rabidfish]

Re: Max RPM

Don's right, get a set that puts you close to the top of the RPM range. Then use 75% - 80% for a cruise speed.

 

[vstol]

Re: Max RPM

it is the 431A engine with the 4 barrel carb so i do not think that there is a rev limiter on it, It came with the B7 props stock, I had gotten a set of B6's off ebay for 125, that is why i am running those now, i had to cut of the B7's due to a siezed fwd prop.

 

[Don S]

Re: Max RPM

What was the rpm with the B7 props before you cut them off? Do you remember or did you ever get a chance to check? You could probably get a good prop shop to repitch your B6's to B7 if you knew what the rpm would be when done.<br />And for those that don't understand his engine numbers, they are Volvo 431A engines with a 290 style DP drive. the engines are V6's.