seems like prop is spinnig out.. but its not the prop ???

[bullard64]

i have a 24 foot toon with a 90 horce force on it, when i give it to much throttle to fast or when its at top speed , (which is just 20 mph buy GPS wth to adults and a baby), and go over waves or rough water its like a car on a wet road spinning. it has a new prop that is 14 '' in daimeter and a 13 dergree pitch. the moter mounted all the way down and it does have the long lower unit on it. marked the new prop and its not slipping. should the boat faster than this and what can i do bout the spinning ??? oh, its also worsh going upsteam.

 

[flycaster]

Re: seems like prop is spinnig out.. but its not the prop ???

i have a 24 foot toon with a 90 horce force on it, when i give it to much throttle to fast or when its at top speed , (which is just 20 mph buy GPS wth to adults and a baby), and go over waves or rough water its like a car on a wet road spinning. it has a new prop that is 14 '' in daimeter and a 13 dergree pitch. the moter mounted all the way down and it does have the long lower unit on it. marked the new prop and its not slipping. should the boat faster than this and what can i do bout the spinning ??? oh, its also worsh going upsteam.

When you bought into a "TOON" you did not get a speed boat.
When in rough water, you will notice that the front of the boat goes UP in the air, in which case the rear GOES DOWN, and the reverse action when going over a wave.
If you were to look over the transom when the back of the toon goes up in the air you will notice that the prop is very close to the surface of the water. When this happens your prop will cause cavitation, where air is sucked into the prop area causing a loss of forward momentum.
When going upstream the water is coming at you and you will loose momentum. It is just like being out in the ocean and trying to swim to shore against a rip tide or current.
Your 20 mph sounds like you have the motor propped OK.

 

[EGlideRider]

Re: seems like prop is spinnig out.. but its not the prop ???

Sound pretty normal for a pontoon. The prop will often ventilate in rough water.

 

[crazyinkc]

Re: seems like prop is spinnig out.. but its not the prop ???

Try to keep as much weight aft as possible. This will help keep the prop in the water. When I bought my first toon everyone wanted to sit in the middle of the boat or up front and the prop would vent very easy.

 

[Micahhaase]

Re: seems like prop is spinnig out.. but its not the prop ???

My 24 foot sweetwater with a 90 hp mariner.. on GPS goes about 22 mph... with 2 adults and 6 kids on board... funny thing is it was going 21 with 4 adults and 6 small kids on it with a full tank of gas and the cooler and all equipment at about 5600 RPM.. I really need to take it out with just me and see what it hits..

 

[jeeperman]

Re: seems like prop is spinnig out.. but its not the prop ???

My father-in-laws boat started doing this too.
It had nothing to do with the propeller being exposed to the atmosphere in anyway.

But it did have something to do with too much boat for the prop and motor.

Make sure your not taking on water. Or loading your boat with too much weight.
These two resulted in the motor turning the prop as it was designed to do. But the boat was too heavy and the prop would turn and "slip" in the water. Not on the shaft nor because it was above surface.

Kinda like doing a burnout from the stop sign, too much power too quicklly equaled lost traction. It happens in water too.

 

[lncoop]

Re: seems like prop is spinnig out.. but its not the prop ???

Seems to be a tad bit of confusion. What we suspect is ventilation, not cavitation. The two terms are commonly interchanged, but they are two entirely different phenomena. Ventilation occurs when air pockets caused by turbulence develop around the prop and cause it to momentarily lose its bite. When this occurs the prop can feel as if it's spinning out. Ventilation is common with barges because there is so much surface area and so many angles making contact with and churning up the water ahead of the prop. It is also normal to experience greater incidence of it in rough water. Not sure what was meant exactly by "exposure to the atmosphere," but I don't think that's what we're talking about here. In any case, 20 mph or so is about right for a 24 footer with an older 90 horse. Some may get a few more mph, some less, but that's about all it's fair to expect of your rig. Finally, if you're not sure about the prop pitch we can speculate as to whether experimentation is in order, but we'll need some more info first.

 

[jeeperman]

Re: seems like prop is spinnig out.. but its not the prop ???

when i give it to much throttle to fast or when its at top speed , (which is just 20 mph buy GPS wth to adults and a baby), and go over waves or rough water its like a car on a wet road spinning.

go over waves or rough water = "exposure to the atmosphere,"

to much throttle to fast or when its at top speed = spinning the prop because it (the engine & prop) cant get enough bite or traction from the water (slip).

 

[bullard64]

Re: seems like prop is spinnig out.. but its not the prop ???

thanks guys... just makes me wonder if i should think about trying to drop the motor down more or back furher from the boat..dont know a lot about boats cause this is my 1st one, but i have been looking at everything and the v-shapped peace that bolts to the bottem of boat and goas toward the front. and the motor mounts too.looks like i could space that whole thing down 2 or 3 inches or maybe even move it back some, but then the stering cable may not reach...would this help any ???

 

[Jeep Man]

Re: seems like prop is spinnig out.. but its not the prop ???

The transom has been designed and placed by people with way more background than us. Usually, the only things that can be improved upon is things that are lacking due to production cost or personal preferences. Placement and transom height would not fall into either of these categories. What you could do to improve your performance would be to underskin the boat, in other words, plate in the underside. This will reduce some of the turbulence coming off the toons, resulting in better water to bite into. There have been numerous posts on this topic.

 

[bullard64]

Re: seems like prop is spinnig out.. but its not the prop ???

i usaully would agree with you on things being designed and place buy people with more background..but from what i can figure out my set up is a 91 model with a force motor which was on there way out and was just throwing anything on these things thay could find, and alot more and better designs have come out sence way back when...I also see pontoons in my same size range with 150 horse motors or bigger....is all that hp just a waste ???

 

[lncoop]

Re: seems like prop is spinnig out.. but its not the prop ???

That horsepower is not a waste, but you have to remember your barge was designed and built twenty years ago. A lot has changed since then. The pontoon experience is vastly different than what it was originally intended to be. People tube, wakeboard and ski behind their barges now, but the original concept behind the party barge was just that, a barge to party on. Back then no one dreamed that manufacturers would be adding third toons and 225 horse motors to their pontoon boats. Many people would keep their barges in a slip and trailer their ski boats to the lake, then they would drive the barge to a cove and leave it there for the day. That way, they would have a fast boat to ski behind and a slow boat to chill and eat lunch on. The fact is, your rig is doing what it was designed to do; cruise around at a leisurely pace and provide a stable platform for relaxing. If you want more speed you'll have to invest considerable money in a new barge or major upgrades on the one you have.

 

[bullard64]

Re: seems like prop is spinnig out.. but its not the prop ???

thats kinda what i was saying..and from what i can figure, some of the changes was like the ones i mentioned...motor back further and deeper. i am a millwright/ mechanic buy trade, so all the laber would be done buy me. im not to worried about going much faster..but i would like to be able to pull the big tube around with the kids and grand kids without the prop doing that...its hard to believe that the boat done this when it was new....

 

[lncoop]

Re: seems like prop is spinnig out.. but its not the prop ???

You could try lowering the motor on the pod. That may or may not help, but it's worth a shot if you're comfortable doing it yourself. I wouldn't move it back though. Don't think that would help any, and if you plan on pulling a tube you'll have trouble finding a tow harness to accomodate your modification.

 

[jeeperman]

Re: seems like prop is spinnig out.. but its not the prop ???

thats kinda what i was saying..and from what i can figure, some of the changes was like the ones i mentioned...motor back further and deeper. i am a millwright/ mechanic buy trade, so all the laber would be done buy me. im not to worried about going much faster..but i would like to be able to pull the big tube around with the kids and grand kids without the prop doing that...its hard to believe that the boat done this when it was new....

So is this "slippage" experienced only when your taking off with a tuber in tow ??
(hole shot)
If yes that is cavitation and it will happen no matter how deep you reposition the current prop on the current outboard.
If your exposing the prop when going over waves, (ventilation), lowering the prop will cause it to happen less often.
But not likely worth the effort and expense.

 

[glengold]

Re: seems like prop is spinnig out.. but its not the prop ???

You didn't mention if you have tried to play with the trim based on load/conditions/etc. This is often necessary and a good skill to learn.

For a added effect of the trim, you might consider putting a dolphin fin on the cavitation plate on your LU. I have one on my 16 ft flats boat and it helped dramatically with plane speed and handling rough water. When you trim all the way down, you want the LU to be slightly angled inwards, as to provide upward lift as well as forward thrust. With the dolphin fin you will get more lift as you are essentially adding underwater "wings" to the LU. Some say that the dolphin fins are worthless but in my experience, on an under or low powered boat, they are effective.

 

[lncoop]

Re: seems like prop is spinnig out.. but its not the prop ???

Might find this helpful.
http://www.boatfix.com/how/props.html

 

[bullard64]

Re: seems like prop is spinnig out.. but its not the prop ???

found that the wings (or spoilers) going down the sides of the motor box have broke loose at he welds...talk to a local bot shop and he said that this could make a big diffarance...going to weld them up and see if thats the problem

 

[lncoop]

Re: seems like prop is spinnig out.. but its not the prop ???

Excellent. Hope that makes it ship shape. Let us know how it turns out.

 

[EricJRW]

Re: seems like prop is spinnig out.. but its not the prop ???

found that the wings (or spoilers) going down the sides of the motor box have broke loose at he welds...talk to a local bot shop and he said that this could make a big diffarance...going to weld them up and see if thats the problem

I'd like to see a picture if it's not too much trouble.

Thanks