21P 3-blade to 19P 4-blade, should I go to 21P 4-blade

[bunker108]

Ok, I went to a 4 blade 19 from a 3 blade 21 on an 18ft Caravelle, 4.3 Volvo GL/SX drive for better holeshot loaded heavy. I could spin the 3 blade 21 to 4600 fully loaded but took too long to plane out. Dropping down to the 19 4-blade fixed the holeshot. No problem getting on plane even with seven adult on board. I can easily over rev the 19 though and 5K RPM is easy to reach on the tach.

Is going to a 21P 4-blade the right move? All props in this discussion are Aluminum.

The 21p is the stock Volvo.

The 19P 4 is a Solas

Maybe a 19P 4 blade SS would be ideal?

Will holeshot improve just moving to a four blade without changing pitch?

I am open for suggestions.

I need to double check my gear ratio too, not sure if it is the 1.79 or 1.98.

 

[Starcraft5834]

Re: 21P 3-blade to 19P 4-blade, should I go to 21P 4-blade

I had a 21pitch 3 blade solas on my 19.6 cuddy, with 3.0 Merc, it took forever to get on plane,, like you I put a 4 blade Solas on, it's 15p though.. In my case hole shot was fixed quickly, I now jump on plane in about 5 seconds, that was with 5 adults in the boat. with 5 adults I was 33mph at 4500-4600 WOT.. Im happy with those numbers... make sure your WOT is within "acceptible" range of your motor, you dont want the wrong prop on spinning to quick and potentially damaging the engine..

 

[Slip Away]

Re: 21P 3-blade to 19P 4-blade, should I go to 21P 4-blade

I went from 21P 3 blade to 20P 4 blade. No loss of RPM (5,000) at WOT and only .325mph loss of top speed. Holeshot was dramatically improved. Do it !

 

[Leardriver]

Re: 21P 3-blade to 19P 4-blade, should I go to 21P 4-blade

It's worth a try, but I suspect that you will lose all of the new-found enjoyment.
Just because a engine will physically spin a prop past the recommended range doesn't mean that you have to ever run it there.

You can manually just keep an eye on the tach and don't let it over-rev. Having low end power is awesome.

 

[jestor68]

Re: 21P 3-blade to 19P 4-blade, should I go to 21P 4-blade

If you put the SAME pitch 4 blade on there, expect the WOT rpm to be reduced(more blade area).

The same pitch 4 blade will offer only marginally better acceleration. That's why it is recommended to drop an inch of pitch(3 to 4 blade) in order to maintain present rpm and improve acceleration.

Being able to hit 5000 rpm is not a big issue, since it's recommended not to run over 75% throttle for extended periods anyway.