21p currently... ss21 make that much difference?

[Dante04SRT]

I am noticing that my 21p aluminum prop just isn't cutting it - I've been doing a lot more tubing, skiing and wakeboarding from the boat lately and the holeshot is seriously lacking. The boat is a 21' bowrider with the 4.3 and AlphaOne.

I was thinking originally of getting a SS 19p but am somewhat concerned about top speed lacking too much. Would an SS 21p prop work noticably better or should I stick with a 19p SS?

 

[hwsiii]

Re: 21p currently... ss21 make that much difference?

Dante,welcome to Iboats prop forum and we will try to help you as much as we can, but there is certain information that is needed in order to help you. The following form has all of the information that is needed to help you with your problems in finding the right prop. If you do not know all of the information that is asked for on the form please give us the most information you have available as I have a program I designed to find the right prop for any planing hull boat that needs this information, and most other people who are trying to help you will need the same information. It requires time to find all this information when we have to look for it and in my defense I expect you to be willing to expend as much effort in finding the right prop as I do. We hope to be able to help you get the exact prop you need for your particular uses, and this information is required to do that.
It is not as simple to pick the right prop as most people coming to this forum think it is, that is why we ask so many questions, it is for your benefit we ask all these questions. And if you have a stainless steel prop or are changing to one the blade geometry of the prop can make a lot of difference in speed and RPM.

Iboats Boat and Motor Info

1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make and model of motor
7. HP and gear ratio of motor IMPORTANT
8. Manufacturer?s recommended WOT range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
13. WOT RPM and speed from prop, how much gas and how many people in boat for test data

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.

H

 

[hwsiii]

Re: 21p currently... ss21 make that much difference?

Error

 

[cr2k]

Re: 21p currently... ss21 make that much difference?

A SS21 will take even more from your hole shot. Try a 19p either Alu or SS.

The aluminum prop will spin up faster and give you a better hole shot.
You may not lose that much top end either.

Consider the weight diff between alum and SS and think of how much more it will take to get it spinning.

Have a talk with your local prop guru about a 4 blade 19. May give you better hole shot and top end.

That's a lot of boat for a 4.3 and a 21p prop.

 

[Dante04SRT]

Re: 21p currently... ss21 make that much difference?

OK, here goes:

1: 2007 Ebbtide 200 SE
2: L: hull 18' 8" W: 8' 1" Weight: 2600lbs
3: 4 ppl, 20 gallons of gas
4: Wakeboarding, skiing, tubing
5: Yes, Deep V, can't find deadrise spec (32" of centerline floor depth?)
6: Motor is 2007 Mercruiser 4.3 V6
7: 190hp 1.81 gear ratio IIRC
8: WOT 4800-5000
9: N/A
10: N/A
11: N/A
12: Stock aluminum 21p 3blade
13: Haven't gotten a baseline yet

 

[Dante04SRT]

Re: 21p currently... ss21 make that much difference?

A SS21 will take even more from your hole shot. Try a 19p either Alu or SS.

The aluminum prop will spin up faster and give you a better hole shot.
You may not lose that much top end either.

Consider the weight diff between alum and SS and think of how much more it will take to get it spinning.

Have a talk with your local prop guru about a 4 blade 19. May give you better hole shot and top end.

That's a lot of boat for a 4.3 and a 21p prop.

I'm basing my SS thoughts off of my previous boat. I went from a 19p alum to a 17p SS with my old 3.0 Merc and it made a big difference out of the hole. Very big improvement. That; and I guess I don't like the cupping that I always see on my alum props.

 

[hwsiii]

Re: 21p currently... ss21 make that much difference?

Dante, you should be using 19" pitch prop and a 4 blade prop would help for pulling people out of the water and let you plane at lower speeds as well. Here are my numbers.

Boat and Motor

Prop Picker

H

 

[sleeper]

Re: 21p currently... ss21 make that much difference?

I have a similar sized boat and same engine/drive combo. I went from a 14x21p 3-blade aluminum prop running at max rpm (4800) to a stiletto bay-pro II 4-blade SS prop in a 14x18p. I wanted a prop for watersports, tubing, skiing, kneeboarding. The prop is awesome for watersports. It has an awesome hole shot and midrange is great, stays on plane at lower speeds. My max rpm lightly loaded is a hair over 4900rpm which is a little over the max recommended but I don't ever run there and we aren't lightly loaded very often.

A 14x19p 4-blade SS would be nearly perfect, but my stiletto acts almost like a 19p anyway. I highly suggest a 4-blade though, it made a world of difference.

 

[Dante04SRT]

Re: 21p currently... ss21 make that much difference?

What about the prop diameter? I see everything from 13" to 15". What are the benefits/drawbacks there?

Also, if I do a 4 blade, would I still stay with a 19" pitch?

 

[hwsiii]

Re: 21p currently... ss21 make that much difference?

Dante, what is your WOT RPM and speed.


H

 

[Dante04SRT]

Re: 21p currently... ss21 make that much difference?

Dante, what is your WOT RPM and speed.


H

WOT RPM is 4950 and speed is 45-46mph (if the gauge is correct).

 

[hwsiii]

Re: 21p currently... ss21 make that much difference?

Dante, you need to change to a 21" pitch Solas Amita 4 blade, it will increase your hole shot and acceleration enough to make it easy to pull up your water toys. You can't go to a 19" pitch because it will raise your RPM too high, probably to about 5,200 or 5,300.




Price: $103.99
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Add Amita Aluminum Propeller 1513-140-21 To Your Cart

Propeller Specifications:
SKU:#1513-140-21
Manufacturer: Solas
Brand: Amita
Material: Aluminum
Diameter: 14?
Pitch: 21?
Blades: 4
Rotation: Standard (Clockwise)
Usually Ships Within: 1 Business Day

Please get back with me on your WOT RPM and Speed for my database.



H

 

[ramster]

Re: 21p currently... ss21 make that much difference?

I tried a 14X21 4 blade Amita on my Glastron 5.0 220 HP, and I could only turn that prop to 4200-4300 with a 1.6 drive ratio, holeshot was ok, and my top speed didn't change, but I felt I was lugging the motor too much. My original prop was an AL 14.5X21 3 blade, which I turned to 4600 rpm. Quite a bit of rpm drop for an AL prop, more than I thought it would. If you are at the high end of your rev range with a load, you might be ok with it, I think Solas should make that prop in a 20". I now use a Mich. Wheel Apollo SS 14X20 4 blade, and it works perfect on my boat, great holeshot, rpm's are just over the max at 4900, with a light load. I'm not saying it's the best prop going, it just seemed to the one my boat likes the best.