Prop on 24' Pontoon Question

[mpritch272]

Hello, I have a 24' 2002 SmokerCraft Infinity Fish Pontoon boat, with a 2002 90 HP Johnson 2 stoke (J90PLSN).

We trashed the prop early on a few years ago, and bought a replacement, the dealer couldn't provide me the specs on the old one, so I just picked a 15 pitch (HU1315AO) and went with that.

Since then, we've had what I would guess to be ventilation when pulling a tube, make a turn and sometimes if we push too much the engine will race and we will have a loss of propulsion, we have to pretty much slow down to regain propulsion.

Which direction should I be moving towards, a 13 pitch or 17? I'm thinking 13. We have a lot of nicks and chips off the current, it's time to replace it.

Thanks in advance.

Pritch-

 

[DMAN1968]

Re: Prop on 24' Pontoon Question

I have a 24' Lowes pontoon boat with an older Johnson 115. I recently went with a 14x13 prop on it and haven't had the problems that you say you have. You need to make sure that you prop the engine for the proper rpm or you can lug the motor...A bad thing. You need to get your motor in the upper range of it's limits with a light/med load at WOT. What rpm's are you currently getting at WOT?

Also, mine is very sensitive to engine height and trim. You may have the engine mounted just a bit high, dropping it down an inch or so may solve your problems as well.

The 13 pitch works for mine and the things I do...but your boat will probably requre its own "tweaking" so to speak.

 

[rndn]

Re: Prop on 24' Pontoon Question

I've read that a cupped prop will help to reduce venting, but as stated above it is very important to prop your motor so it can get into the upper limits of the suggested rpm range.

 

[mpritch272]

Re: Prop on 24' Pontoon Question

dman1968, is that 14x13 a 14" x 13 pitch?

Thanks, I'll try to check existing WOT rpm if I can get the boat in the water this weekend-

rndn, which cupped manuf would you recommend?

 

[DMAN1968]

Re: Prop on 24' Pontoon Question

Yes, mine is a 14" diameter with a 13 pitch. 14" is about the largest diameter that my gearcase will allow...yours maybe different.

 

[rndn]

Re: Prop on 24' Pontoon Question

Any mfg as long as the prop is cupped. I bought an SS Turning Point for my application and it works great, however your application is different than mine.

 

[Tiki Barge]

Re: Prop on 24' Pontoon Question

I know this is an old posted question, but I have exacly the same problem with my 20' pontoon with 70 merc.
I purchased a replacement prop from the marina and it was supposed to be an exact match? But there you go, that weird problem. Did you ever solve the mystery?

 

[Silvertip]

Re: Prop on 24' Pontoon Question

You folks with pontoons should consider large diameter four blade aluminim props. Most prop manufacturers including the engine manufacturers have pontoon props. A prop is a prop but there are specific characteristics like large blade area and four blades that helps to push these barges.

 

[tomxdana]

Re: Prop on 24' Pontoon Question

Check this site out it has a prop calculator. It should put you in the ballpark.
http://turningpointpropellers.com/propellers_101_cm.htm

Good luck

 

[DMAN1968]

Re: Prop on 24' Pontoon Question

Unfortunately, the design of a 2 log pontoon boat seems to invite ventilation problems...or so it seems from other post I have read. Engine height, trim angle and proper weight balance on the boat all seem to be really big factors in how much of a problem it is.

I have no experience with the four bladed props so I can't offer much advice there. A cupped propeller did seem to help my old 50 hp Johnson on my pontoon as did the addition of a doel fin, but the doel fin on my 115 made it ride bow down so in that case it was more of a hindrance than a help.

My best advice: start with the engine at its lowest setting on the transom, get the prop pitch (I agree with the large diameter idea) that will get your engine into its upper rpm range at WOT, then adjust engine height until you just start to get ventilation...then drop the motor down one hole.

That should get you the best overall function. Worked pretty well for me. I still have to test it with a full load on the boat yet (meaning 10 of more people) but I am pretty sure it will do fine.

 

[mpritch272]

Re: Prop on 24' Pontoon Question

I ended up buying a 14 x 13 pitch prop, haven't had a chance to put it on yet...

The boat didn't ventilate originally, but started after I replaced the prop the 1st time. I'm hoping this pitch change will help.