Pontoon speed?

[Chilly5001]

Hello, first time poster, long time lurker.

I have a 22' 1996 crest II DLX with a 1996 75 hp force by merc 2 stroke. Top speed (as measured by gps) is 15 mph with 2 adults and canopy up. Rpms are about 4600-4800. Not sure what prop pitch is (or even how to find it). Have had the boat for about three years and this is consistent each year. Should it be going faster? I realize there a lot of factors at play but any thoughts would be appreciated.

 

[WaterDR]

You just need to know what the rpm range is for that motor.

 

[WaterDR]

My guess is the actual rpms should be 5500, but I am not sure. If that is the case, you would need to pitch it back.

 

[Scott Danforth]

how deep is your anti-cav plate in the water? If it is too deep, it will drag. In a pontoon, first get the motor height right, then look at props and pitch.

 

[Chilly5001]

Not sure about the anti-cavplate...will check it out and report back. For what it's worth, I found some info on iboats that says the rpm range is 4750-5250 for my motor. Thanks for everyone's feedback.

 

[HotTommy]

I don't think I'd pay a lot of money for a new prop to gain 400 RPM. ... Drag is what keeps the speed down. Water drag on a pontoon boat is largely determined by how much weight it is carrying. Wind drag is determined by how much air you have to push around with the fences, canopy, etc. I'd be surprised if everything you could possibly do would gain you more than 5 MPH more. You'll have to decide if its worth the money and effort.

One more thing to illustrate the point about weight: My 24' pontoon boat with 150 HP motor will hit almost 29 MPH with just me aboard. Add three more adults, two kids, ice chest, etc. and my top speed drops to about 25 MPH.

 

[steelespike]

Usually the prop size is near the base of the blades or under the prop nut.
We do need your prop size to make any sense of your numbers.
I think it will feel peppier and hold speed as you add weight better.
!5 is pretty slow And it may be possible to tweak up to 18 or 20.
Prop size will really help.

 

[lmuss53]

I'm on my third pontoon boat and I keep them propped so they run at the top of the RPM range with a moderate load. Doing this makes for a much more responsive throttle and a more maneuverable boat at low speeds and around docks. I would reprop this boat to get it up to around 5200 to 5300 RPM at WOT with a moderate load. You will get a more pleasant boat to operate and maybe a couple more MPH.

 

[Chilly5001]

Thanks again for the feedback...hope to get to the lake next weekend and will see what I can find.

 

[Chilly5001]

Ok, so it's been more than a week or two but have had scheduling issues getting to the lake. Finally made it this weekend and found/did the following:
-convinced the wife to help me scrub toons with scrubby pad (80% done)
-attempted to change water/fuel separator (hasn't been done since I boat the boat 3 yrs ago and I bought the wrong blasted filter....but at least I dumped it out)
-found that back section of one toon had a broken vent cap and had been letting water in....hand pump majority of water out.
-found an extra prop (numbers are F10.38 x 13p - hope this means something to y'all) and put it on
-took off old prop. Thing looked beat and has numbers 48-85632-11 on it.
-put new(ish) prop on and she did 4200 rpm at wot but I got 17 mph. Load was about the same as historical (gear, gas people,etc).
-I checked the anti cave plate while under way and it was at the top of the water...didn't look too deep to this novice, but consider the source.

Thoughts? Thanks as always!

 

[Chilly5001]

No Title

Old and new prop

 

[Silver Eagle]

My 24 ft . with 90 hp Merc two stroke gets me around pretty easy at 3600,rpms mph. steady .With two or three Adults.about 18 mph. I can do this all day long and hardly use any gasoline..If I kick it up Are around 4500 rpms it'll go 22mph The motor is an 07 oil injected..

 

[Seon]

...I found some info on iboats that says the rpm range is 4750-5250 for my motor...

...put new(ish) prop on and she did 4200 rpm at wot but I got 17 mph.
Thoughts? Thanks as always!

Your rpm is way too low. You need to re-prop it back to a13 pitch.