Switching to 4-Blade
 

I am considering switching to a 4-blade prop and want a second opinion on pitch.

I have read several previous discussion on the site, but have not found one yet that answers my question specifically.

Existing Prop: 3-blade SS 21-P (vented)
Boat: 1995 Barchetta 182
Engine: 4.3L Vortec
Drive: Alpha 1 LX

WOT: ~48mph
RPMs @ WOT: 4900 to 5000

Reason for switching: Wakeboarding... Hole shot is fine, but I have to hammer the throttle down fully every time. I would like to stress the engine a little less, and I don't care if I lose a couple MPHs on top end (rarely get to go that fast anyway). I also hear that I would have better speed control and planing ability at lower speeds. And finally, I would like to go to an aluminum prop to help protect the drive, just in case.


So, the question...

What pitch 4-blade should I go to considering I am a touch above my recommended WOT RPMs with a 21-P 3-blade? (my thought is a 21-P 4-blade, but it could be a 20-P 4-blade)

And

Are there any prop manufactures to avoid?

Here are two I have found in a brief search:

Solas RUBEX 4 Aluminum Boat Propeller #9513-140-21 for Mercruiser Sterndrive Alpha One 4.3L 155 - 210 HP - iboats

Michigan Wheel Vortex Aluminum 4-Blade Propeller from Wholesale Marine

Finally, if anyone could point me in the direction of a cheap prop wrench, I'd appreciate it.

Thank you for your time,

Kris

Re: Switching to 4-Blade
 

bump.

Re: Switching to 4-Blade
 

No need to bump these posts.

Seems odd that you are already at 4900 rpm WOT with a 21" pitch prop. Normally you would be down around 4600rpm but maybe your outdrive gearing is slightly different.

Anyway, i run a 20" - 4 blade Michigan Wheel Apollo SS prop on mine and my WOT rpms are 4900. I also have a 19" 3 blade aluminum that has me hitting 5000rpms and a 21" - 3 blade aluminum that has me at 4600rpms at WOT. The 20" 4 blade is a good compromise prop and is reasonably good for wakeboarding & tubing.

As for avoiding prop manufacturers, the only one i personally would 'avoid' is those plastic/replaceable blade Piranha props for anything other than a spare 'get me home' prop.

Re: Switching to 4-Blade
 

Thank you for the response. I bumped the post (sounds like hockey) as I realized this thread had fallen off the main forum page without a response.

Your input gets to the point of my question. Considering I am at the top end of my WOT range with a 21-P 3-blade (i don't know why, and I also find this a little odd), should I be going with the standard advice of dropping 1 inch in pitch when switching to a 4-blade?

I guess if I am looking for an easier hole shot, the 21-P 4-blade may not get me there. So, I had better go with the 20-P 4-blade and just watch the RPMs nearing WOT? Please let me know if you agree.

Thanks again for your time,

Kris

Re: Switching to 4-Blade
 

That 1" drop in pitch along with the change from 3 to 4 blades will likely increase your rpms by 300 at WOT....but, sometimes the change in prop rake etc from one prop to another offsets a bit of that rpm change so the change could be as low as 150 or as high as 450. You should be able to make the change & just dont run it full throttle for any length of time.

You might want to give that small dial on the back of your tach a few spins & then re-set it to "6cyl" to see if it reads any differently.

Re: Switching to 4-Blade
 

Just returned from Florida with a 4 blade SS 18p.
It replaced a 19p aluminum 3 blade.
Picked up a solid 2mph... 41.5 vs 43.5
I'm really impressed with the feel of it.
I did see more torque load while crusing at mid throttle, but it went away at higher speed.
I have no zinc fin to counter torque, but will soon.

It is a Michigan Wheel Apollo #993204, about $300 during a sell at iboats

Re: Switching to 4-Blade
 

Thank you for the additional responses. I think I am going to go with the Michigan Wheel Votex 20-P 4-Blade.

It is said to have cupped blades so it doesn't increase the RPMs as would normally be expected. Additionally, I want to make sure I get an easier hole shot, so I don't want to offset any benefit of a 4-blade with too large a pitch.

I will also spin the dial on the back of the Tac and see if it changes anything.

I will report my results (hopefully positive).

Thanks again and have a great day,

Kris

Re: Switching to 4-Blade
 

Just a thought, are you positive that your prop is a 21 pitch? because you can have them re-pitched at a prop shop.... If someone did that previously to you owning it, it would explain why you are at 4900 RPM.

Re: Switching to 4-Blade
 

Good point. Although the prop is stamped as a 21P, there is a chance it was modified by the previous owner.

Either way, I am going with the 20P, so we will see if I will have to watch the RPMs at WOT or if it will put me right in the correct range as most other people have experienced with my hull and engine type.

Thank you,

Kris