18' pontoon prop?

[Bushmasta]

My first boat, 16 Suntracker 18' DLX party barge with Mercury 60 hp. We live in Montana at about 4200' I took it out today for the first time, 4 people, trolling motor and some wind 5-15 mph and at WOT it was only about 4600 rpm, GPS speed 14.6mph, I had about 25 gallons in the 32 gallon tank.

1. Is that bit slow? I thought more like 18-22 as posted on suntracker site, or was that under ideal situation with one person.

2. I thought it would be more in the 5500 rpm at WOT?
My prop is 11p and 13".

 

[HotTommy]

With 5-15 MPH winds, it make a big difference whether you are going into or with the wind. When you can get a calm wind speed with your usual load, note your WOT RPM. If it is less than 5500, you may get some benefit from a different prop. Take your data and visit the Mercury Prop Selector website to see what they recommend. ..... My personal opinion is that your speed seems about right to me for the conditions you describe.

 

[lprizman]

Weight to power ratio....temper your expectations...
New boat and motor?

 

[ahicks]

My bet is you have too big a prop - and a piece of that may be lack of tuning for altitude of 4600 ft.

With the engine tuned for altitude (if necessary, I don't know, you'll need to look into it in owners manual) you should be turning up about 5500 rpm or so for best performance.

 

[Starcraft5834]

My first impression is you have to much prop..(pitch to high), 18 footer with 60hp on it... even if you are propped correctly, you'd be luck to hit 20 mph. I have a 2019 20ft toon with a 115 merc on it... calm and lightly loaded... 30, maybe 31 mph

 

[Starcraft5834]

With 5-15 MPH winds, it make a big difference whether you are going into or with the wind. When you can get a calm wind speed with your usual load, note your WOT RPM. If it is less than 5500, you may get some benefit from a different prop. Take your data and visit the Mercury Prop Selector website to see what they recommend. ..... My personal opinion is that your speed seems about right to me for the conditions you describe.

yup agree.. might be over propped a little

 

[DeepCMark58A]

It is a pontoon not a real high performance hull. It is a barge not a sport boat.

 

[lprizman]

It is a pontoon not a real high performance hull. It is a barge not a sport boat.

I've seen some pontoons push over 80mph....it can happen

 

[Captain Greg]

my 20 foot pontoon with 60 Johnson top out at about 15

 

[DeepCMark58A]

I've seen some pontoons push over 80mph....it can happen

Sure but is it agile and responsive?

 

[DeepCMark58A]

I should explain myself and my position on pontoons, I live on a lake have a dock with a pontoon and a sport boat that works for fishing or pulling a skier or a tube. Sure you can pull a skier with a pontoon but is it ideal?

 

[ahicks]

Clearly a 'toon is at best a compromise for pulling duty. Still though, the ski boat/runabout numbers are decreasing just as pontoon numbers are climbing. That in mind, we're reminded all boats are a compromise to some extent.

 

[Rabbit929]

2020 21ft Sylvan dual 25" toons, 90HP Yammy here with a 13 1/2 12in pitch prop, and just me is 26 mph @ 5900rpm.
Full load, pulling a tube with 3 people on it, 18 mph @ 5200rpm.
Im also looking for some way to get a little more speed out of it, like a tubing specific prop.
No, a pontoon is not ideal, but a regular boat is far from ideal for my needs. I would also like to find out what i gotta do to make this pontoon the best of all worlds. If i use the yamaha prop seletor they seem to point towards a 14" diam 9" pitch prop, but i wonder if that would make me go any faster or just raise my rpms a bunch?

 

[ahicks]

2020 21ft Sylvan dual 25" toons, 90HP Yammy here with a 13 1/2 12in pitch prop, and just me is 26 mph @ 5900rpm.
Full load, pulling a tube with 3 people on it, 18 mph @ 5200rpm.
Im also looking for some way to get a little more speed out of it, like a tubing specific prop.
No, a pontoon is not ideal, but a regular boat is far from ideal for my needs. I would also like to find out what i gotta do to make this pontoon the best of all worlds. If i use the yamaha prop seletor they seem to point towards a 14" diam 9" pitch prop, but i wonder if that would make me go any faster or just raise my rpms a bunch?

I can pretty much guarantee that prop will raise rpm's without going any faster for sure.

Similar boat with similar speeds here

 

[DeepCMark58A]

Clearly a 'toon is at best a compromise for pulling duty. Still though, the ski boat/runabout numbers are decreasing just as pontoon numbers are climbing. That in mind, we're reminded all boats are a compromise to some extent.

No law against having more than one boat.

 

[ahicks]

No law against having more than one boat.

I was one of "those guys" with a really nice (expensive) ski boat on a lift across from a pontoon boat for many years. Then I noted a couple of seasons in a row that the ski boat was being pulled at the end of the season with the same tank of gas it was launched with. Clearly it wasn't being used, and it was time for it to find a new home.

Nothing against having 2 boats, or 4 boats for that matter - as long as you can justify their existence.

 

[Bushmasta]

So went out today, still a tad windy. By myself I could get 5200 rpm and 18.5 mph. 15.5 mph with 4 people, 4900 rpm. I can't get into that ideal rpm as specified by Mercury. Drop to a 9' prop?

 

[Bushmasta]

I have a 2016 18' party barge 60hp. I bought it from a guy in WI, near sea level. I'm in MT at 4400'. 1st time out, 4 people, windy day, WOT, 4900 rpm, 14.5 mph via GPS. 2nd time out, 4 people less wind about 15 mph, 4900 rpm. Just me in boat, I could get 18 mph, 5200 rpm, WOT. Mercury recommends 5500-6000 rpm WOT, so should I go from 11px14 to 9px14 prop?

I've been told I should have a high altitude prop? I've also noticed that the last 2' in the throttle don't change RPM at all, does the cable need to be adjusted? New to boats.

 

[WesNewell]

Check your manual again. I think you'll find wot rpm to be 5500-6000 rpm. And yes, you should lower your pitch to increase rpm.

 

[ahicks]

I think you're darn close to having everything that motor has available at 4000'. I also think that maybe a 9" prop is going to put you over 6000 rpm. If you absolutely have to have every last drop, I would try to find a 10" prop, or possible have an 11" prop repitched at a prop repair facility.

To be honest though, I don't know what you're trying to gain with the exercise. From your test results, I'd say if you think there's an additional 5 mph hiding somewhere, there's not. 4 stroke motors don't need to turn up max rpm to get max performance like a 2 stroke might....