Prop ?

[tbcb7271]

I just bought a 2019 suntracker 22dlx with a mercury 115hp. I'm trying to figure out how come the boat tops out at 20mph, at full throttle it's running 6200rpm. I don't currently know what prop I have on now but I'm sure it's not the right one ?

I'm pretty new to the pontoon thing so any help would be great. I did do some reading on TAPS and lifting strakes, it was a great article where they were comparing taps vs strakes on the same boat size as mine. TAPS took the win with 1.5mph more.

 

[JimS123]

You were not very specific so I can only guess. My assumption is you have a "Std." 4-stroke that runs at 5000-6000 rpm. Thus, for optimum performance you need to increase your prop pitch by 1 increment (2 inches). That will put you into the proper range.

You have a toon, not a speedboat, plus you don't have a lot of HP. The "correct" prop may give you a little more speed, but it is not going to be a worldbeater.

Before you do anything, verify the RPM and speed. Factory tachs aren't always correct, nor are factory speedometers.

 

[tbcb7271]

You were not very specific so I can only guess. My assumption is you have a "Std." 4-stroke that runs at 5000-6000 rpm. Thus, for optimum performance you need to increase your prop pitch by 1 increment (2 inches). That will put you into the proper range.

You have a toon, not a speedboat, plus you don't have a lot of HP. The "correct" prop may give you a little more speed, but it is not going to be a worldbeater.

Before you do anything, verify the RPM and speed. Factory tachs aren't always correct, nor are factory speedometers.

I read everyone with the same engine and size boat running 27-30mph so I'm confused. I will change the prop to stainless and the pitch.

 

[JimS123]

I read everyone with the same engine and size boat running 27-30mph so I'm confused. I will change the prop to stainless and the pitch.

That expensive change will serve no purpose until you can verify that your data is correct.

 

[legalfee]

What Jim says. Verify that you don't have water in your pontoons and your motor is running right. Then verify with a good tach what your RPMs at WOT is. Then find out your MPH using GPS. Once you find this out then you can go about finding the right pitch for your prop. The numbers on your prop will tell you what pitch you have.

 

[ahicks]

I agree. No stainless prop required to make a pontoon boat as fast as possible.
If it's a 4 stroke I would try to get the rpm down to 5500 or so, to make the motor sound less busy. It'll make at least very similar power and speed, but could be a mile or 2 an hour faster.

If you are

 

[jlh3rd]

just for comparison. I have a 24' 06 lowes pontoon with the original 60hp merc. big foot. When by myself, I've hit 20 mph (gps) . I'm expecting delivery of a new Merc 115 hp command thrust motor in July. I hope, and think, there's something going on with your boat as with the money I will spend, I'll be more than disappointed....

 

[ahicks]

just for comparison. I have a 24' 06 lowes pontoon with the original 60hp merc. big foot. When by myself, I've hit 20 mph (gps) . I'm expecting delivery of a new Merc 115 hp command thrust motor in July. I hope, and think, there's something going on with your boat as with the money I will spend, I'll be more than disappointed....

I find it pretty interesting as well! 6200 rpm and 20 mph don't sound right to me either. But until we know more (like prop dimensions for instance) and maybe get those speed/rpm numbers verified, it is what it is.

Our 90 hp Honda (4 stroke) powered 24' toon is good for 24-25 mph@6200 rpm with a 13" prop, and 25-26mph@5500 rpm using a 15" prop. 4 strokes don't need to turn right at max rated rpm to make best power, where a 2 stoke might...

 

[jlh3rd]

I feel better now....

 

[jlh3rd]

forgot i posted
I got my new motor in july, the 115 merc. I get 26-27 mph ( gps). This is just me on board. The full bimini top is up, and running a mercury spitfire, 4 blade 14x14 prop and am turning about 56-5700 rpm. 24' twin, 25" pontoons
happy...

 

[QBhoy]

forgot i posted
I got my new motor in july, the 115 merc. I get 26-27 mph ( gps). This is just me on board. The full bimini top is up, and running a mercury spitfire, 4 blade 14x14 prop and am turning about 56-5700 rpm. 24' twin, 25" pontoons
happy...

Excellent. These are amazing engines. I’ve one on a cuddy. Way more powerful than 115hp for sure.
All I’d perhaps say, is that after lots and lots of prop testing on my CT 115…I find these engines are at their very best if they can run close to 5900/6000 rpm flat out. Anything less than 5800 rpm with a prop…and I find it makes them so much worse on fuel cruising and everywhere else in the rpms. Sweet spot for mine is around 3600/3700 rpm cruising at mid 20’s. At her best, she’ll run up to just over 6000 rpm at mid 40’s gps. She’ll hit the limiter at around 6100 rpm occasionaly and depending on what prop I have on her. I go between a 19” tempest plus and an enertia 20”. The tempest runs incredibly well on these CT 115’s. I’d urge you to take advantage of the props you can run on the CT. so many amazing props available for them.

 

[jlh3rd]

actually, funny you said that as I'm looking to try the 14x13 Hustler 4 blade because with multiple adults on board and some teenagers on tubes, I'm down to about 17-20 mph and 5200-5300....
So, yep, I wanted to be up higher in the rpm's. That is the only 4 blade, aluminum, 14x13 i can find......I am curious what a 15x11, would do, but I don't have that kinda money to be trying props.

 

[QBhoy]

actually, funny you said that as I'm looking to try the 14x13 Hustler 4 blade because with multiple adults on board and some teenagers on tubes, I'm down to about 17-20 mph and 5200-5300....
So, yep, I wanted to be up higher in the rpm's. That is the only 4 blade, aluminum, 14x13 i can find......I am curious what a 15x11, would do, but I don't have that kinda money to be trying props.

Understandable. Being a pontoon (something I know nothing about) and perhaps needing very small pitched props, you may be limited. Is it the CT model you have, just to be sure ? You should look into what props are available to you, if she is. Having tried a good few on my CT now. There is 100% serious gains to be made with a well suited prop on these.

 

[jlh3rd]

yeah, it a long shaft, CT 115, and the standard version, not sea pro, or commercial.
Pontoons are different and can cause cavitation/ventilation issues. I had to lower the motor to the last mounting point because of that. It worked but I was worried it wasn't....I have max up trim now, no blowout...We'll see what the 14x13 does next year

 

[jlh3rd]

update....so that hustler prop won't work on my CT gearcase as the prop hub is too small...as discovered by info from this site....
so a black max, 3 blade, 16x13 is on...will test come late april....
If it doesn't do what I want, Im going with a spitfire 4blade, 14x12....

 

[jlh3rd]

update FYI....got on the river today, windy and a little rough. I saw 27 mph and 6000 rpm with the 16x13, 3 blade.......where i wanted to be