Top speed

[Poppas poontoon]

I have a 20ft pontoon with a 90 2 stroke merc. Now i have no guages its basic as they come. I used my phone gps to find out the speed and im getting 27 with myself on the boat. I figured i should be getting at least 30 mph is this about right or should it ve doing 30 35 mph? Now i have a 13 1/4 ×20 ss prop at least thats whats engraved on the side of it. Any help would be great. TIA

 

[Scott Danforth]

Welcome aboard

your 27mph is actually higher than I would have guessed.

prop/motor height is a big issue on toons. get that right prior to doing anythign

also, a 20 pitch prop seams a bit steep. get a tach to see what you are turning at WOT. if you lug the motor.....you kill the motor.

 

[ahicks]

Our 24' toon w/Honda 90 is good for 25-26mph turning a little over 5K while using a 15" pitch prop. 13" pitch prop on the same boat turns a little over 6k (sounds really busy) and makes about the same speed.

Similar power on a lighter boat going a little faster no surprise here, but doing it with a 20" prop is a surprise! Thinking your rpm's might be on the low side, and a little less pitch may help the boat pick up another mile or 2 per hour. Worth a try if you could borrow a 17 or 19" prop

 

[Poppas poontoon]

Im gonna have to try both of yalls suggestions. Im not sure about the height bc where i have it at now its all the way down on my transom. And thats far enough bc if i try trimming it up just a tad brings the water intake out the water

 

[Starcraft5834]

ive got a new 20 foot toon with 115 merc command thrust.. only pushed it to WOT 1 time thus far. was closing in on 30 while trimming it up....the new 115 came with a 15p 3 blade... it's a big prop with big blades.... was bout 5500 rpm area when I pulled the stick back down.... was flying pretty good. tons of power to ski and tube with..

 

[legalfee]

I have a 1995 Sylvan 824 Special Edition with a 90HP Force. I only get 18mph with two people on board and WOT at 5500 RPM. My pontoons need cleaning and that would help.

 

[Gemstone1]

"My pontoons need cleaning and that would help"......I was amazed at what built up crud on pontoons will do to top speed...I went from 41 mph new to 28 mph after sitting in the water one season.....I cleaned it with a pressure washer, and got it back to 39 mph.

Regards
Gemstone1

 

[legalfee]

"My pontoons need cleaning and that would help"......I was amazed at what built up crud on pontoons will do to top speed...I went from 41 mph new to 28 mph after sitting in the water one season.....I cleaned it with a pressure washer, and got it back to 39 mph.

Regards
Gemstone1

Mines been in the water a couple of seasons. Unfortunately I don't have a trailer or a truck. I can borrow a trailer and a truck and I definitely need to.

 

[legalfee]

Mines been in the water a couple of seasons. Unfortunately I don't have a trailer or a truck. I can borrow a trailer and a truck and I definitely need to.

Got my pontoon back from the shop. They acid cleaned the pontoons. They also drained, patched, and pressure tested them. I was getting 18 MPH with just me on the boat now I'm getting 22.5. My WOT RPMs have gone up to 5900 from 5600. I would have thought I'd gotten more MPH.

 

[ahicks]

There's a saying that is regarding putting perfume on a pig that might apply here. "Toons are not built to go fast and improvements like the one you just got are hard to come by. There may be a little more left on the table, but it's going to be about coming up with (by way of experimenting) the perfect engine height and just the right prop - and if you get that nailed, you may find another 2-3 mph, or you may not.

 

[legalfee]

I think you're right. I could go with a 17p prop and gain another 2-3 MPH but use more gas.