Too small of a prop?

[Yellow Yota]

So, I understand the pitch of a prop. Lower pitch equals lower top speed, more RPM at a given speed, and quicker hole shot.
My question is, can a prop with too little pitch hurt your hole shot?

I have a 21 foot 2004 Rinker RX-1 with the 330 HP 350 Mag engine. The prop is a stainless 3 blade 17" pitch. I was very surprised to see that prop on the boat. I think it's the original equipment, but I'm not positive. I just bought the boat and have only had it in the water once for a test drive.

It runs awesome, and as expected with such a non aggressive prop, top speed is almost 50 MPH. That's where it hits the rev limiter. The concern is that it isn't real fast out of the hole. I haven't timed it or counted boat lengths; just seat of the pants feel here. It's not a dog by any means, but it wasn't as quick as I thought it might be for such a powerful motor and such a low pitch prop.

Our test drive was with 3 200-250 pound men aboard. No other gear except a few life jackets. I need to see what it does with 6 or 7 on board, but I imagine it will still rev to the limiter. I'm not looking for a race boat by any means. This is a toy puller. I don't care how fast I get across the lake. I'm here to relax. I ain't in a hurry if you get me. We don't have freak lightning storms in my area that I need to outrun. If I can comfortably cruise at 35, that's fine. I just want to be able to pull someone out of the water when I have 6 people in the boat. At least as well as this boat will be able to. I know, it's not a comp boat. I don't expect that type of performence. I just think with my motor and boat size, it should be somewhat impressive.


So. What I want to know, is could a more aggressive prop get out faster than one that is so mild?


Thanks in advance for advice, thoughts, and suggestions!
Chad

 

[steelespike]

Re: Too small of a prop?

Not a prop pro but I'll try to get you started.
I think we can tell a little better if we had your actual rpm at max speed also
your gear ratio.What diameter is the prop.You can measure from center to the tip of one blade.
If you know the brand/model of prop.Some props have stern lift others have bow lift.Bow lift could slow hole shot.I think a 4 blade prop will get you up quicker.
The pros should be along with more specific info.

 

[Yellow Yota]

Re: Too small of a prop?

I will provide more info tonight. I believe that max RPM (elecronically limited) is 4800-4900 rpm. Max speed is 49-50 mph. I'll get the rest for you folks when I get home!

 

[Yellow Yota]

Re: Too small of a prop?

Alright. The diameter looks to be about 15 3/4". Just looked the prop number on Prop Gods, and they list it as a 15 1/2" diameter.

It's a Mercury Marine Mirage Plus.

Part# from the prop is: 48-18278 17P


No idea what my gear ratio is. I have an Alpha One from 2004 if that helps.



Again, many thanks!
Chad

 

[steelespike]

Re: Too small of a prop?

As far as rpm goes you do need to increase your pitch.2" would drop the rpm about
300 to 400 It seems to me it would handle a 21 pretty easily.
Not being able to get to its actual rpm makes it difficult to be specific.
If it tends to zoom right up to the 4800 then the 21 is probably in order.
You should stick with stainless ,same brand for more stable results.You may be able
test a prop if you intend to buy at your local marina.

 

[Yellow Yota]

Re: Too small of a prop?

As far as rpm goes you do need to increase your pitch.2" would drop the rpm about
300 to 400 It seems to me it would handle a 21 pretty easily.
Not being able to get to its actual rpm makes it difficult to be specific.
If it tends to zoom right up to the 4800 then the 21 is probably in order.
You should stick with stainless ,same brand for more stable results.You may be able
test a prop if you intend to buy at your local marina.

While I appreciate your input and understand exactly what you're saying, it really doesn't answer my question. Unless I'm missing something.
It appears that you're advising me on how to get the most top speed at the same time as limiting my RPM by drag at about the same time the rev limiter would normally kick in. I haven't tested the boat with a full load yet, so I'm not concerned about that end of it yet. I'd love to put a 21 or so pitch prop on to get some good speed just for the fun, but not if it'll compromise what I bought the boat for.

What I'm looking for is info on how to get on plane faster. I'm curious if a prop that is too "small" would slow that action down.