Max RPM Prop size question?

[ward_cleaver]

The mercury website lists max rpm for my 150 optimax as 5250-5750. When sizing a prop do I try to shoot for 5500rpm? My dealer moved my motor up 2 holes and he's suggesting a change from a 14-1/2" 17" 3blade prop to a 14-1/2" 19" 4 blade. how does this sound to you?
My boat is a Tahoe 215 ob deckboat.
Is it safe to run this motor at 5500 rpm? for how long?

 

[Dhadley]

Re: Max RPM Prop size question?

You'll shoot for 5700 or so with a normal load. How long can you run it there? How much time (and gas) do you have? Obviously with a deckboat you'll probably find a nice relaxing cruise speed and run there a lot. But there's no reason - enginewise - you couldn't run wide open for hours on end.

 

[codertimt]

Re: Max RPM Prop size question?

As for the prop size, what rpm are you running at WOT with the current prop? Have you ran the boat since the motor was raised? I would suggest getting numbers as currently rigged before investing in a prop. Also, and this is a wild guess(but somewhat confirmed by the turning point prop selector), but I would think that a 19" would be alot of prop for a 150 on a big deck boat....even a four blade.

If your planning on doing any skiing/tubing(again guessing since we don't know you're intended use....but that seems like a reasonable guess for a deck boat) with more than a few passengers aboard you might need to think about going the other direction in pitch...

With current performance numbers and intended use the experts here can help you out a lot more...

 

[ward_cleaver]

Re: Max RPM Prop size question?

I'll test it this weekend for skiability, wot rpm and loaded with partyers and get back to you! me wife