Pontoon Boat & Deck Boat Forum

I am currently in the process of rehabbing my pontoon. My plans include upgrading the motor from a 50hp to a 90hp. The new 90hp is almost twice the weight of my old motor.
Has anyone filled their motor pod with expanding foam to add floatation? I found this product http://www.shopmaninc.com/foam.html but I don't have any experience with it. It supposedly is for marine applications and is resistant to water and solvents.

I'm just wondering if I would see any added floatation when the boat is stationary.

Probably not. The foam will absorb water and actually make it heavier. Eventually it will sit lower than it would without foam.

There's a reason that boats are designed with weight and HP in mind. The main one is center of gravity. Adding weight in one area without compensating for it somewhere else can mess with the mean and make the boat unstable. The added power and speed of a bigger HP engine will enhance that instability.

It's best to stay within the manufacturer's capacity and engine recommendations. Going above that can open a can of worms in liability issues.

If, of course, the manufacturer has set a maximum of 90 HP or above, you're good to go, as the additional HP and weight were engineered into the design.

My boat is rated for 120hp. As far as absorbing water, the manufacturer claims the following: Common Applications: Our 2LB density marine foam is recommended for void filling in nonstructural applications. This product can be poured underneath decks and inside cavities where a lightweight flotation foam is needed to provide buoyancy. This foam has been tested in accordance with U.S. Coast Guard Regulation # 33 CFR 183.114 . This foam is approximately 95-98% closed cell which resists absorbing water, however continuous water submersion can eventually lead to loss of buoyancy over a period of years. We recommend this product strictly for flotation applications. If looking for a liquid foam for sculpting or casting we recommend using at minimum our 3LB or 4LB density. More questions? [Try our Foam FAQ.]

I trailer my boat back and forth to the lake so prolonged submersion wouldn't be an issue.

If your boat is rated for 120 h.p. I don't think a 90 h.p. motor will be too heavy. I would skip the foam idea. If it was a good idea then the manufacture would have done it to start with.

I honestly don't see how foam will add buoyancy inside of a pontoon anyway. If you think about it, its encased in aluminum. It should just add weight. I've always heard that the foam that is used in them is to eliminate the need for pressure chambers, like Premier, Bennington and Manitou, that I am aware of use (and others I'm sure) and resist dents if smacked against something. If you look at the old foam dock floaters, they sit no higher in the water than and plastic hollow ones. I may have to experiment on an empty beer can or 18 in our pool. Good way to kill a few beers, if anything! Craig! Whatcha doin next weekend?

OK I was thinking his motor pod that is usually filled with water while idling or sitting still. If I was wrong then, yes it makes no sense to foam a pontoon.

I'm not sure if foam would help but it could easily be removed if it didn't. (not in a pontoon of course )

Bryden24shp wrote:I honestly don't see how foam will add buoyancy inside of a pontoon anyway. If you think about it, its encased in aluminum. It should just add weight. I've always heard that the foam that is used in them is to eliminate the need for pressure chambers, like Premier, Bennington and Manitou, that I am aware of use (and others I'm sure) and resist dents if smacked against something. If you look at the old foam dock floaters, they sit no higher in the water than and plastic hollow ones. I may have to experiment on an empty beer can or 18 in our pool. Good way to kill a few beers, if anything! Craig! Whatcha doin next weekend?

Yeah I agree about filling a pontoon with foam being useless. If anything it would decrease bouyancy because of the added weight. Displacement is displacement. However I'm considering filling just the motor pod, because when the boat is stationary it is filled with water. If foam displaced the water then that would add floatation. My dilemma is how much displacement would I gain. I'm sure I would gain some floatation, but would it be enough to be worth the effort.

I recall seeing photos and a write-up last year of someone who filled their new pontoon water glide with foam. I looked but could not locate the link. If we could track it down, he might be able to share personal experiences with using foam filler. Anyone else recall seeing it?

Ask yourself how many gallons of water is in your motor mod that you want to displace at about 8 lbs per gallon do you think you would displace about 6 plus gallons totaling about 50lbs. if so then put something that weighs that amount on the back of your pontoon and see how much lower it sets in the water that will be how much higher your boat will set and you'll see if it's worth adding the foam.
I think you'll be wasting your time & money.

Van.

Bryden24shp wrote:I honestly don't see how foam will add buoyancy inside of a pontoon anyway. If you think about it, its encased in aluminum. It should just add weight. I've always heard that the foam that is used in them is to eliminate the need for pressure chambers, like Premier, Bennington and Manitou, that I am aware of use (and others I'm sure) and resist dents if smacked against something. If you look at the old foam dock floaters, they sit no higher in the water than and plastic hollow ones. I may have to experiment on an empty beer can or 18 in our pool. Good way to kill a few beers, if anything! Craig! Whatcha doin next weekend?

I agree with Bryan... not sure on next weekend... you have something in mind? Hijacker!

Cabinetman wrote:Ask yourself how many gallons of water is in your motor mod that you want to displace at about 8 lbs per gallon do you think you would displace about 6 plus gallons totaling about 50lbs. if so then put something that weighs that amount on the back of your pontoon and see how much lower it sets in the water that will be how much higher your boat will set and you'll see if it's worth adding the foam.
I think you'll be wasting your time & money.

Van.

If the pod is open to the water you won't be displacing any weight, only adding flotation with the foam.

Glenn

Cabinetman wrote:Ask yourself how many gallons of water is in your motor mod that you want to displace at about 8 lbs per gallon do you think you would displace about 6 plus gallons totaling about 50lbs. if so then put something that weighs that amount on the back of your pontoon and see how much lower it sets in the water that will be how much higher your boat will set and you'll see if it's worth adding the foam.
I think you'll be wasting your time & money.

Van.

Good idea.

After taking some measurements today, I don't think I would see any benefit. I think I'll just save my money and maybe look into a third toon next year.

The third toon with a motor mount is the best option I think. Its what I did, and i'm happy with it. It may not be the ticket for all but mine works perfectly!

I bought my pontoon with a 75HP motor on it. I added a third log with motor mount it raised my boat about 4 1/2" in the stern I then put a 250 motor on it and I'm still about 3 to 3 1/2" higher than my boat orginally set and a lot smoother ride.

Every time I try to fill mine with foam, it just runs out the back. Maybe I'm drinking the wrong cocktail?