will underprop mean overrevving?

[hudman]

if an engine is under propped, in other words, using too low a pitch, will it make it over rev or will it stop at the max operating rpm? I have a new 6.2 horizion 383 mag motor in a 27 rinker with a bravo 2. install is complete, going to test this sunday, starting off with a 17 alum 3 blade, then going to switch to a SS 4 blade 18p. wondering if I should borrow a 21p alum for testing sake, WOT on this motor is reccommended at 5200, thanks for your help<br />PS the guys in the prop section were no help

 

[I/O WALDO]

Re: will underprop mean overrevving?

The fuel injected merc.engines have a rev limiter on the ignition to prevent WAY overrevs(will kick-in knott much over 5200rpn).If the prop is too mild it can run past max w.o.t. and get into the limiter.Those big diameter props on B2s are a touchy subject on proper pitch.What size-weight-type boat?

 

[Boatin Bob]

Re: will underprop mean overrevving?

You might want to try and take at least a 19 aluminum, I've always heard if going from a 3 to 4 blade you want to drop an inch of pitch so if you have a 4 blade 18 then maybe a 3 blade 19? Also might want to post this in Prop section to be sure the "experts" see it.

 

[hudman]

Re: will underprop mean overrevving?

its a 6500 lb boat, v configuration. I asked the prop section, they are more geared towards small outboards, it seems.<br />I own a 17 p 3 Blade alum now, and a 18P 4 blade stainless, which is equilivent to a 19P 3 blade alum. I was going to borrow a 21P alum 3 blade so i could do proper testing.

 

[tommays]

Re: will underprop mean overrevving?

I think i would fully break in the motor BEFORE i started pushing bigger props <br /><br /><br />tommays

 

[hudman]

Re: will underprop mean overrevving?

you know, i ve talke to the factory, they just say, do not run at ANY continous rpm for over 5 min, and try not to run under 1500 rpm for the first hour. I thought the same, but apparently these days thats not the case<br />of course , i wont be out there wide open in the first 5 min, but after a hour or so of planing off, crusing at different speeds, ill try the WOT test if all looks good<br />This is a MERCRUISER factory crate motor, complete