Move from 3 blade to 4 blade ?

[Texasbikers]

I have a 2005 Ebbtide 24' Funcruiser deckboat I
350 Mercury Magnum
Lake use in Middle Tennessee
Poor out of the hole performance
Had 800 lbs of humans on board yesterday, all in rear half of the boat and could not get past plowing, would NOT plane, had to move 375 lbs of humans to the front to get up on plane.

Only had 30 gallons of fuel on board, not loaded down with lots of equipment.

Currently I have a Mercury Marine Vengeance 3 blade Stainless Steel 19 P prop.

WOT was 4300-4400 RPM yesterday. Recommended WOT is 4800-5200 RPM

We generally cruise across the lake, pull 2 or 3 big bertha tubes at times... Typically carry a load of 800-1000 lbs of humans.

I think I want to go to a 4 blade prop, should I go with a 4 blade 18 P or 17 P to increase the WOT RPM closer to the recommended range ? I want a strong hole shot.

I am looking at a 4 blade Mercury alum prop... any thoughts on this? I know stainless is better, is that "better" a performance thing or just a strength thing? (like if the prop hits something) I'm seeing HUGE price differences.

Thanks everyone.

 

[fossill]

Re: Move from 3 blade to 4 blade ?

I like aluminum for many reasons.
I run a Merc aluminum 4 blade prop and it performs very well.
Should I ever decide to get a stainless steel prop, I would go for the Merc High 5.

 

[walleyehed]

Re: Move from 3 blade to 4 blade ?

1 prop that has proven to work quite well on that style of boat is the Stiletto bayPro series and is available in 18P and with the properties of this prop i can't help but think it would help a bit with hole-shot-not sure how much though-and should get your rpm up on top-end due to the over-all lifting ability of this prop. And yes..it is a 4bld.

 

[steelespike]

Re: Move from 3 blade to 4 blade ?

while a prop change can surely improve your performance its not unusual to have to move some people around to plane easier.It appears you had about half your rated load in the rear portion of the boat.I wouldn't expect it to behave well even with
a different prop.Just as you might increase tire pressures and move the load around in your car/boat trailer when packing for a 2 week vacation.Sometimes an adjustment is in order

 

[DuckHunterJon]

Re: Move from 3 blade to 4 blade ?

The difference between aluminum and stainless is the stiffness of the blades. Aluminum props past a certain HP will slightly flatten out at higher rpms, thus losing thrust. Stainless deform less. At least, that's the way it was explained to me.

 

[walleyehed]

Re: Move from 3 blade to 4 blade ?

The geometery of the blades of an SS prop cannot be copied by aluminum just due to the properties of the materials used. This goes back to understanding that a certain pitch number meens little if you don't understand the intended design.