How about using an aluminum boat for a third pontoon?

[CTD]

I just bought an 18 ft pontoon boat. I have been reading about people adding a third pontoon or strakes and would like to improve preformance. With 2 people it runs good enough for me with the 40hp evenrude but with 4 people on board it loses a lot of speed. I have an 11ft aluminum boat that was abandoned so it is free, it would fit under the pontoon boat with about 8 inches clearance on each side and the bottom would be about 7 inches above the bottom of the pontoons so it would support some weight. So what do you think, would it work, is there too much turbulence under the boat?

 

[kmarine]

You are adding more resistance and weight, The manufacturer spent much time and effort to engineer a safe boat. Are you getting the best performance from your motor? try new spark plugs or change the prop if you need to perform better with more load. Larger boats with a third pontoon are maintaining stability under higher horsepower engines and higher speeds.

 

[Scott Danforth]

you would have to seal that small boat to make it into a toon log. otherwise the splashing underneath the pontoon will fill it up and your pontoon may actually sink.

in this case, free would cost you more.

if you want to add a 3rd log, go ahead. however you will not realize any significant performance with only 40hp (or even 90hp). people with a third log generally have a lot more hp.

if it was me, I would invest in a grill and cooler on the pontoon and use it for what its designed to do. slowly cruise with a coctail in hand.

 

[HotTommy]

I agree that the boat would have to be water tight with a vent to be of any use at all. Further, the structure of the aluminum boat might be subjected to forces greater than it is built to withstand. More importantly, you are considering a change that can only be evaluated after it is done. You'd have to seal the boat, mount it to the underside of your pontoon boat, and take it for a ride to see if it helped or hurt. My wild guess is that such a project offers about a 10% chance of improving performance, a 60% chance of diminishing performance, and a 30% chance of structural failure within the first 20 hours. ... Given the cost of time and materials to try this out and the likely outcomes, I wouldn't do it if it were my boat.

P.S. Will it still fit on your trailer with the boat beneath?

 

[1983 ercoa 21']

Think this has been tried before with out success!

adding a third toon is your best bet
be prepared to change motors I had a 115 before and after adding a third log and it slowed down! Now I'm running a 150.
the biggest bang for your buck would be to under skin your pontoon.

 

[lncoop]

It's an eighteen foot toon with a forty horse. If the motor's running correctly and you don't have water in the tubes or some other remediable issue there's nothing you can do to improve speed or performance that wouldn't require far more money than it would make sense to spend on that boat. If everything is ship shape run her and enjoy or upsize the rig.

 

[Silver Eagle]

My answer is just Hell no. Take it for what it's worth.

 

[FrizFreleng]

I may have seen the same idea decades ago proposed by Jethro Bodine. Politely suggest you leave it alone and resume destroying your liver.