3 blade vs. 5 blade SS props

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swansont

Seaman
Joined
Jul 6, 2004
Messages
71
Haven't been on the site in a while, boat's been under tarps since my son left for the Army. So, he is home on leave, asked me to bust out the boat, (along with the $1K to get tires, batteries, gasoline, etc.) Anyway, yesterday, launched it, had a pretty good load on, but even when I dumped some bodies, had a heck of a time planing out. So, I have two props that came with this boat;

1987 21' Sea Ray Monaco, Cuddy.
Listed for 350/Alpha One, came with 454/Alpha One
Prop that was on yesterday; SS, 5-blade, 13 1/4", 21 pitch PN#48-815760-21
Prop that came also, but not tried, SS, 3 blade, 14 1/2-3/4", 21 pitch, PN# 48-89802-21

So, larger diameter 3-blade prop, same pitch, better or worse for hole shot, planing out issues? Top end speed is not really an issue at this point in my life. Rather be able to plane out quickly, but have a hole shot for tubes and what-not.

Ideas?
 
H

hidef

Lieutenant
Joined
Aug 22, 2009
Messages
1,465
Re: 3 blade vs. 5 blade SS props

The three blade prop will give you a better hole shot. The five blade is more efficient and is acting more like a 23 pitch prop than a 21. At wide open throttle you should see somewhere around 200 RPM or maybe more in difference between the two props with the 3 blade turning high RPMs.
 
S

swansont

Seaman
Joined
Jul 6, 2004
Messages
71
Re: 3 blade vs. 5 blade SS props

So, I can grab the hole shot/planing issue with the three blade, sacrificing some top end, correct? I was in the process of changing the props out right after I posted this, figured , just give it a try, right? Well, the 3-blade is large enough that I will have to carve my anode up to gain clearance. Not wanting to do that for no good reason than curiosity, and knowing that I'll have to drop the lower unit to install the anode that belongs there if I'm not satisfied, think I'll wait till winter, can check the water pump and renew it. Thinking about freshening the heads also, valves seem to be floating at about 4000-4250 rpm, just some light popping, but seems like it might be time. Anyway, thanks for the reply on the props!
 
86 century

86 century

Ensign
Joined
Sep 8, 2009
Messages
986
Re: 3 blade vs. 5 blade SS props

You dont haft to drop your lower to pull the anode it comes off first.
It can be left off long enough to test the prop. I am running without mine now due to the new prop being to large.

I just went from a 19p three blade to 17p four blade. My hole shot got much better, top end fell off by three mph.
 
S

swansont

Seaman
Joined
Jul 6, 2004
Messages
71
Re: 3 blade vs. 5 blade SS props

That's right, you access that bolt the top........had forgotten that. Thanks! Have to do a test Wednesday, trying to get out.
 
Tail_Gunner

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: 3 blade vs. 5 blade SS props

swansont said:
Haven't been on the site in a while, boat's been under tarps since my son left for the Army. So, he is home on leave, asked me to bust out the boat, (along with the $1K to get tires, batteries, gasoline, etc.) Anyway, yesterday, launched it, had a pretty good load on, but even when I dumped some bodies, had a heck of a time planing out. So, I have two props that came with this boat;

1987 21' Sea Ray Monaco, Cuddy.
Listed for 350/Alpha One, came with 454/Alpha One
Prop that was on yesterday; SS, 5-blade, 13 1/4", 21 pitch PN#48-815760-21
Prop that came also, but not tried, SS, 3 blade, 14 1/2-3/4", 21 pitch, PN# 48-89802-21

So, larger diameter 3-blade prop, same pitch, better or worse for hole shot, planing out issues? Top end speed is not really an issue at this point in my life. Rather be able to plane out quickly, but have a hole shot for tubes and what-not.

Ideas?
Click to expand...

Im very sure you have way to much prop going on there...Similar boats run 17-18 p props. Put the 21 3 blade on it will help some...The goal is to keep the boat at about 4800 rpm at wot...Now if you dont gear it in that fashion you are over taxing your motor at all rpms which is not good.

If you would like to pursuit it a bit reply back but a quick off the shelf solution would be a 17 p 4 blade aluminum about a 100 here at iboats...Solas is a good mfg
 
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