Pontoon took a Dive - under water

[willyg1997]

Greetings,

New to the forum. I have searched this topic, but have not found the advice I am looking for.

Last spring I finished a complete rebuild on my first ever Pontoon. Great fun, but I experienced the pontoon taking a dive on two occasions. Both instances we doing about 10 mph.



The first time it took a nose dive, was due to the lack of "my" experience with the pontoon (too much weight in the front). Lesson learned the hard way. Nobody was hurt, but made a nice mess in my shorts. The second time took me by surprise, as most of the weight was in the back. I let off the throttle fast and it dove, water was a little choppy, but not bad. I thought maybe I had some water in the tubes, but when I got back to shore and opened up the drains, they were empty. Again, another lesson learned.

So, I am learning that the pontoon is just not a big barge that floats, and takes some learning. My pontoon pictured is 20" with a 25hp. It has 3/4" pressed fiberglass flooring, so it is about 1/4 of the weight of marine plywood. With my rebuild I move the front railing forward 2' to allow for more inside sitting room, which probably is a contributor to the diving.

I have learned how to drive the pontoon without it diving and the proper weight distribution. Having kids on board makes me very tense especially when above idle.

My question is.
Is there any type of system that can be fabricated to help minimize the depth of dive if and ever it should take a dive again? Possibly adding an aluminum plate under the front of the pontoon between the tubes, (50"x18") at a 45 deg with supports..? Acting like a boat would, lift instead of dive. I know I could add a third tube, but I have a hard enough time with the little 25hp.

And yes, I understand weight distribution, water condition, and water in the tubes, are all the main factors why a pontoon would dive. But as far as safety for my grand kids go, I just want to make sure I have a little more safety protection then the knife blade deck platform.

The pics are from during my build (Before, during, and after), Sorry I don't have any on the water. But at least it give an idea on how it is laid out for weight distribution.

Thanks in advance!!
Bill

[PlaynDoc]

I'm certainly not a boat builder nor marine engineer, but you mentioned moving fence forward during rebuild.... did you add extra weight? or, is your furniture too far forward? how deep are the tubes, when anchored? if the tubes sit fairly deep, it could indicate the boat is overloaded, resulting in nose dive.

[Comstocker]

I'd be looking for the original manufacturer sticker that listed the passenger weight limits to help see where you're at. It looks like you've added quite a bit of new furniture which is all added weight, though I admit it looks very nice!

A 20' pontoon might be rated for 10-12 people, a lot depends on the size of the pontoons. You have to find out what it was originally rated for and start doing some math!

It looks like the water line is above the middle of the pontoon which I don't think is a good sign!

[ron nh]

Also with 25hp there's no weight on the back.

[mpilot]

Also with 25hp there's no weight on the back.

Suntracker had this problem with some of their 24 foot boats back in the day, I think in the 1980's. They sent people a pony toon which was basically an 8-10 foot pontoon that bolted under the front of the boat. That might be something to consider.

[willyg1997]

The sticker I believe is 10 people, don't remember the max weight is of hand. Normally we have between 4 to 6 adults.

When anchored empty the back of the tube is aprox 1/4 under water and the front is even less. The line above the center of the tube was from big upside down sitting in water for a period of time.

The new furniture is very light. Plus with the fiberglass flooring the pontoon is less weight then oem weight. The weight with motor is around1500#.

When loadded with 8 adults the back water line is about 2" below center line and the front is around 4" below center line.

So I think the level height is ok. For the most part.

[willyg1997]

Also with 25hp there's no weight on the back.

Very true. I've been wanting a 40 horse 4 stroke but I've been worried about the extra speed as it may amplify the diving

[willyg1997]

Also with 25hp there's no weight on the back.

Suntracker had this problem with some of their 24 foot boats back in the day, I think in the 1980's. They sent people a pony toon which was basically an 8-10 foot pontoon that bolted under the front of the boat. That might be something to consider.

I will check in on that pony toon. Thx

[PlaynDoc]

The sticker I believe is 10 people, don't remember the max weight is of hand. Normally we have between 4 to 6 adults.

When anchored empty the back of the tube is aprox 1/4 under water and the front is even less. The line above the center of the tube was from big upside down sitting in water for a period of time.

The new furniture is very light. Plus with the fiberglass flooring the pontoon is less weight then oem weight. The weight with motor is around1500#.

When loadded with 8 adults the back water line is about 2" below center line and the front is around 4" below center line.

So I think the level height is ok. For the most part.

Well, here's what I suggest.... As people board, remind them that your boat is *more* than a pontoon boat - it's a SUB-TOON! No extra charge for the thrill of nose-diving! Self-Cleaning Front End!

[teecro]

Curious what HP is the boat rated for?

My first impression is that without adequate HP your motor has no power for lifting the bow and as you add passengers with any attempt at speed you are just making the plowing worse.

Perhaps simply carrying some extra fuel in the very back may help?

[BoatCop]

Your pontoons might be sectioned. Meaning that there could be 2 or 3 chambers in each pontoon. Sometimes there are drain holes between the chambers. Sometimes there aren't, or they could be plugged. Just because no water drains out the rear, doesn't mean that there isn't any water in the front.

Call the manufacturer with the HIN (Hull ID Number) and ask if the pontoons are chambered and what you can do IF there's water in them.

[mrlouis]

What is the length of the boat and diameter of the pontoons, older toons came standard with 23" toons which will cause this problem diving into waves, otherwise if your bow is low you have to much weight in front

[willyg1997]

Curious what HP is the boat rated for?

My first impression is that without adequate HP your motor has no power for lifting the bow and as you add passengers with any attempt at speed you are just making the plowing worse.

Perhaps simply carrying some extra fuel in the very back may help?

Spec says 90hp, which in my opinion is really hard to believe.

[willyg1997]

Your pontoons might be sectioned. Meaning that there could be 2 or 3 chambers in each pontoon. Sometimes there are drain holes between the chambers. Sometimes there aren't, or they could be plugged. Just because no water drains out the rear, doesn't mean that there isn't any water in the front.

Call the manufacturer with the HIN (Hull ID Number) and ask if the pontoons are chambered and what you can do IF there's water in them.

Good to know. That is exactly what it feels like. I will check with the manufacturer. Makes perfect sense. If that is the case, I will weld in a bung in each section. I do know there is one vent tube on the top of the toon. Thx

[willyg1997]

What is the length of the boat and diameter of the pontoons, older toons came standard with 23" toons which will cause this problem diving into waves, otherwise if your bow is low you have to much weight in front

Per my first post it is 20' long. Not sure what the size of the toons are. It is in storage up north.