Propeller Pitch Question

[ADGator76]

I am currently running a 27" prop on a 2000 OX66 VMAX 225, powering a 20'2" Skeeter. In my current configuration, the motor will spin this prop, relatively easily at 6K rpm. I generally run at 5700 WOT, which is already 200 rpm above recommended. My question is this: would it be more prudent to buy a new 29" prop, or have about 2 inches of cup added to the blades of my current prop. My goal is to get the rpm down some where I don't have to worry about over trimming and turning 6k. I want to be able to trim all the way out and top out no more than 5600-5800. I've read that every inch of pitch increased, will decrease the rpm by about 150-200, so a 2 inch increase, via either cup or a new prop should put me in that range, but is it better to cup the current or buy a new one alltogether. If new is a better idea, any recommendations? Thanks for any input.

 

[Part-time]

Re: Propeller Pitch Question

How much prop slip are you getting???
Prop Slip Calculator
If you are getting too much slip then rework your prop so it grabs better.
If you are getting very little slip then go up in pitch.

That's the way I would go about it anyways...

 

[ADGator76]

Re: Propeller Pitch Question

I couldn't get the calculator in your link to show me the actual slip, but I did use the formula on that site and if I figured it correctly, I'm getting ~8% slip, which I believe is within reason (I saw something there that said most high performance rigs are going to get 7-12%). Basically, the speed formula said, at 5700 rpm (where I try to keep it when wot) I should be running 80 mph. At that rpm, with just me in the boat, I get 74 mph, so a difference of 6. 6/74=.08

 

[Part-time]

Re: Propeller Pitch Question

here's another one you can try.

but if it truely is 8% I don't think you will be able to do much better with that prop.

 

[ADGator76]

Re: Propeller Pitch Question

That one calculates the same as the formula I used from the other site at 8% slip. Assuming that is an acceptable amount, I guess the answer is getting a higher pitch prop. I'm thinking a 29" would be perfect, but the highest pitch I'm finding is 28 (not just on this site, but several I've chekced). Any recommendations?

 

[dan02gt]

Re: Propeller Pitch Question

That one calculates the same as the formula I used from the other site at 8% slip. Assuming that is an acceptable amount, I guess the answer is getting a higher pitch prop. I'm thinking a 29" would be perfect, but the highest pitch I'm finding is 28 (not just on this site, but several I've chekced). Any recommendations?

ADGator76, I get 11.38% slip when I run your numbers. With a SS prop you need to add 1" to pitch when using the calculator to account for cup. That being said you have room for improvement. A 27P prop should be plenty for that setup.

What prop are you running?
When was the last time it was repaired? Does the cupping look good on it?
How does it lift your bow?
Do you have a jack plate? If so what is your prop to pad measurements?

Here's a good link to show you how to measure that if you don't know how: How to measure prop to pad height

 

[steelespike]

Re: Propeller Pitch Question

While your numbers seem reasonable you might confirm that the tach is accurate.
I also found 11% slip.

 

[ADGator76]

Re: Propeller Pitch Question

ADGator76, I get 11.38% slip when I run your numbers. With a SS prop you need to add 1" to pitch when using the calculator to account for cup. That being said you have room for improvement. A 27P prop should be plenty for that setup.

What prop are you running? Other than knowing it's a stainless prop, I don't know the brand or style, I'll have to check.
When was the last time it was repaired? Don't believe it's ever been. I've only had the boat about a year and a half. I got it from my father when he passed away.Does the cupping look good on it? Yes
How does it lift your bow? Doesn't seem to have any issues, at any RPM.
Do you have a jack plate? Yes, but it's a manual.If so what is your prop to pad measurements? I've never measured, so I don't know offhand.

Here's a good link to show you how to measure that if you don't know how: How to measure prop to pad height

Thanks for the diagram on the prop to pad distance. I didn't know that was something that could factor in.

 

[jestor68]

Re: Propeller Pitch Question

That one calculates the same as the formula I used from the other site at 8% slip. Assuming that is an acceptable amount, I guess the answer is getting a higher pitch prop. I'm thinking a 29" would be perfect, but the highest pitch I'm finding is 28 (not just on this site, but several I've chekced). Any recommendations?

The Yamaha web site lists their V Max series 3 blade props as available in pitches up to 29" (14-3/4 X 29). They are available vented and non vented.

 

[ADGator76]

Re: Propeller Pitch Question

The Yamaha web site lists their V Max series 3 blade props as available in pitches up to 29" (14-3/4 X 29). They are available vented and non vented.

I saw that and I've found two sites online that actually sell that prop, but I was hoping to find something a little cheaper. Those two sites are coming in at well over $700 for one and almost $1k for the other.

 

[jestor68]

Re: Propeller Pitch Question

I saw that and I've found two sites online that actually sell that prop, but I was hoping to find something a little cheaper. Those two sites are coming in at well over $700 for one and almost $1k for the other.

Yes. I say that US Boat Supply had it for $900! I believe that I'd check around for a reputable shop to massage that prop; i.e., add an inch of pitch and more cup to bring down that rpm closer to the recommended max(5500).

Or, if you're presently running a 3 blade, sometimes a 4 blade(more blade area) will pull the rpm down at the same pitch.

 

[ADGator76]

Re: Propeller Pitch Question

Or, if you're presently running a 3 blade, sometimes a 4 blade(more blade area) will pull the rpm down at the same pitch.

I was thinking of maybe going that route, but doesn't the additional blade take away from the top end? Most of what I've read seems to suggest that anyway. I really don't want to lose any speed, if I can avoid it.

 

[dan02gt]

Re: Propeller Pitch Question

ADGator76,

Your high RPMs and slightly high slip numbers is very symptomatic of the motor being too high. Correct motor height is critical on a high performance boat, and your jack plate makes it easy to adjust. So try to lower your motor down using a 1/4" at the time and see what you get. You will know when you have it right when your RPMs go down but your speed stays the same.

Also like steelespike said you may want to have your tach checked.

If lowering your motor doesn't help call Mark Croxtan at Mark's props Mark's High Performance Propeller he does all the prop work for the guys at Bass Boat Central and can tell you exactly what you need done to make your prop perform or he can recommend a replacement.

Also most guys that run Yamaha props on bass boats use the M1 or T1 I think the main difference is the diameter. That being said the hot bass boat props at the moment are the Mercury Tempest Plus for a 3 blade or a Trophy Plus for a 4 blade. Your can get them new for around $500.00 but you'll need the Yamaha hub kit.

 

[ADGator76]

Re: Propeller Pitch Question

Thanks for the info Dan. I'll give the lower jackplate setting a try next time I take it out and see how that works out for me.

 

[Dhadley]

Re: Propeller Pitch Question

You might think about the Turbo Fusion 4 series. I know where there are some 28s & 29s very reasonable. The Fusions work well on Skeeters.

 

[ADGator76]

Re: Propeller Pitch Question

So, I lowered the jackplate (what a pita that was, stupid hand cranking) and had the boat out today. Although I could still trim out past 5600-5700, it started chine walking and was actually riding very comfortably at 5600 and 73mph. I guess that was the trick, since trimming out any more than that wasn't getting me any more top end anyway. Thanks for the advice, all and I'm still considering a 28 or 29 inch prop, but at least for now, it seems like wide open doesn't really leave a whole lot of extra room, like it was doing before.

 

[dan02gt]

Re: Propeller Pitch Question

So, I lowered the jackplate (what a pita that was, stupid hand cranking) and had the boat out today. Although I could still trim out past 5600-5700, it started chine walking and was actually riding very comfortably at 5600 and 73mph. I guess that was the trick, since trimming out any more than that wasn't getting me any more top end anyway. Thanks for the advice, all and I'm still considering a 28 or 29 inch prop, but at least for now, it seems like wide open doesn't really leave a whole lot of extra room, like it was doing before.

No problem. It sounds like you're well on the way to getting it setup. I have a Rapid Jack manual plate that easily adjustable on the water and I bet I spent two hours playing with it to get it dialed in.

 

[Texasmark]

Re: Propeller Pitch Question

How much prop slip are you getting???
Prop Slip Calculator
If you are getting too much slip then rework your prop so it grabs better.
If you are getting very little slip then go up in pitch.

That's the way I would go about it anyways...

Degree of cupping controls this. If uncupped, cup it; if cupped, have a prop shop increase it.

At the higher speeds, cupping can effect as much as a 2" increase in pitch. So with what you said, I think I have a reasonable answer for you to consider.

Mark