Replacement Pontoon Prop - Updated with new prop results

[Scooch_2]

I have a older 17' Gruman Pontoon with a 2003 Yamaha 70HP 2 stroke. It currently has a Quicksilver Black Diamond 13p prom (numbers stamped on the prop are TA2032 13). With 4 adults on the boat WOT is only 4800 and 20Mph. To get to the proper RPM range at WOT, I am planning to move down to a 11p propeller.

After going through the prop finder, I am looking at the Solas props. A few questions.

Anyone have experience with moving to a Solas Aluminum or SS Solas prop on a Pontoon. Any recomendations for a better prop to consider.

I'm debating the Aluminum vs SS prop choice. It seems 50% of the threads I have read seem to stay the SS is not worth it on a slower boat like a pontoon, the other 50% seem to cure hunger and baldness after installing a SS on the pontoon.

When ordering a prop, is it necessary to buy a new nut kit or other accessories? What I have seems to be in good shape.

Any other suggestions?

Thanks,

Bob

 

[jestor68]

Re: Replacement Pontoon Prop

Re: Replacement Pontoon Prop

I think that you'll need to go down to a 10" pitch to get the rpm up to 5400-5500 rpm. A quick look at the prop section indicates no SS props for your motor below 11 pitch.

Yamaha makes a "Pontoon Performance Series" line of SS props in 14" diameter by 9-13 pitch, in one inch increments. That means they make a 14 X 10 SS prop especially designed for pontoon boats; but it's likely only available through authorized Yamaha dealers.

 

[Scooch_2]

Re: Replacement Pontoon Prop

Re: Replacement Pontoon Prop

If I go with the quicksilver prop, do I want the "extended cup version"

 

[steelespike]

Re: Replacement Pontoon Prop

Re: Replacement Pontoon Prop

I don't pretend to know as much as the gurus but lets take a look.
We need to be sure we are starting with an ideal setup.
Are the logs clean?Have you played with motor trim and height?
No doubt a ss prop would be ideal but pretty costly and there are al props that perform close to that of ss.
Are your saying you normally run with 4 adults? Seldom with fewer aboard? What is the rpm and speed with one aboard?
Is the motor in excellent tune, prop in excellent condition?

 

[Silvertip]

Re: Replacement Pontoon Prop

Re: Replacement Pontoon Prop

You also need to make sure the tach is accurate and that the engine is making full power. A prop is not a fix if something else is wrong.

 

[Scooch_2]

Re: Replacement Pontoon Prop

Re: Replacement Pontoon Prop

Yes, the motor is in tune, I recently rebuilt all the carbs and services the lower unit. The tach was installed at a dealer by the previous owner when the motor was installed. It is the digital yamaha guage and after checking all of wiring it appears correct. The tach shows the correct rpm at idle, so I don't have reason to believe it is off.

The logs are pretty clean, I did my best to get any junk off of them when I had it out to work on the carbs. They were fairly clean with some small growth on them that I was able to get off.

As for the normal load, it is more commonly 2 addults and my 2 younger kids. I have not had it out recently with that load, but as far as I can remember it was about the same RPMs. I also did play with the trim a but while underway with not much difference. As for the height of the motor, that I am not sure about. I will check it later today and see where it sits in the water.

 

[steelespike]

Re: Replacement Pontoon Prop

Re: Replacement Pontoon Prop

Raising the motor might help speed a little especially if height is exceptionally low.
Pontoons disturb the water so much the ideal height could vary widely from boat to boat.
I usually suggest if you don't experience any venting issues that you could raise the motor.
If you look up Yamaha performance reports for 70 hp pontoons both 4 and 2 stroke(I believe same gear ratio)
I see typically 13" props though also as low as 9" It appears to me that pontoon performance is all over the place for no obvious reason. If your pontoon diameter is relatively small you may lose more speed/rpm as you add weight.

 

[jestor68]

Re: Replacement Pontoon Prop

Re: Replacement Pontoon Prop

If I go with the quicksilver prop, do I want the "extended cup version"

It may will help to reduce the ventilation that pontoons are famous for.

 

[Scooch_2]

Re: Replacement Pontoon Prop

Re: Replacement Pontoon Prop

Thanks, I ordered it and hopefully can get it and test this weekend. Will report back. Thanks for the information and advice.

 

[Scooch_2]

Re: Replacement Pontoon Prop

Re: Replacement Pontoon Prop

I received the new Quicksilver Black Diamond 14" 10 pitch prop this week and I installed today. I took the boat out with just me and my65lb son. On a failrly windy and choppy lake, we are not between 5600 and 5700 rpm and 23mph. That is 800-900 rpm increase and 3 Mph faster than last test with 4 adults and 2 kids. Probbaly will hea back out tomorrow with at least 2 adults and see how it performs. The motor sounds happy at WOT, I just need to find a sweet spot at lower RPMs when going down the creek I am on where it is all no wake. It seem smooth between up to 1200 RPMs and above 1800. Between 1300 and 1700 is seems to be be rougher than the old prop. Will mess with the trim and make sure I have the carb's dialed in properly.

Thanks for the help, I think I should be in a fairly good spot now.

 

[steelespike]

Re: Replacement Pontoon Prop

Re: Replacement Pontoon Prop

Nice to see that you apparently have an increase in performance.
Unfortunately the numbers don't seem to add up. Using a gear ratio of 2.33
and 5700 rpm at 23 mph slip is under 1% Not possible with a pontoon.
My guess is either the rpm is actually higher, speed is lower (though 23 seems reasonable)Or the 2.33 ratio is not correct.
A more typical slip would be around 20-25%.

 

[jestor68]

Re: Replacement Pontoon Prop - Updated with new prop results

If you ordered the "extra cup" version, if might act like an 11 pitch. In that case, your slip number might be around 8-10%.

I suggest you order a Solas Rubex hub # RBX-108 to fit your Yamaha. It is interchangeable with the Mercury Flo Torque hub; but fits much tighter when torqued down (60 ft lbs). It should get rid of that chatter you feel at low rpms, that is an unfortunate characteristic of the Merc design, as it does not fit tightly in the hub.

 

[Scooch_2]

Re: Replacement Pontoon Prop - Updated with new prop results

I did order the extra cup version, so possibly that helps explain the difference. I still need to do the test again with a few extra adults in the toon in calm conditions to see how the numbers look for the pre-test. I will have to doube cleck the torque on the nut to see if the hub seated itself more after I took it out for a run.

If I swap the hub for the Solas, how do I get the mercury hub back out?

 

[steelespike]

Re: Replacement Pontoon Prop - Updated with new prop results

Its highly unlikely the prop would run as low as 10% on a pontoon.
Using a gear ratio of 2.33 with 10% slip and 23 mph the motor would be turning about 6300 rpm.
Rated rpm is 6000. I think we need to figure out where we are really at.Motor won't be happy at 6300 for long.
Is the speed by GPS?

 

[Scooch_2]

Re: Replacement Pontoon Prop - Updated with new prop results

Went out today with 4 adults and the top speed was 20mph at 5400 RPM. Assuming the extra cup 10P prop behaves like an 11, I'm around 17% slip. Assuming the tach is accurate, does that sound more appropriate?

 

[steelespike]

Re: Replacement Pontoon Prop - Updated with new prop results

Assuming the 10" is calculated at 11" 17% while really low seems possible.
I think I would try to confirm the tach is accurate.Perhaps you could borrow a shop tach or use a lazer tach.