3 pontoon houseboat convert to 2 pontoons

[TANSL]

Two smaller pontoons, conveniently separated, can give more initial stability than two pontoons, whatever their size, little separated. Everything depends on how the pontoons are and how they are located. If we talk about longitudinal stability, the longest pontoons, be two or three, can give more stability.

On the other hand, the space between pontoons is not easy to use. There is only air and water between pontoons.

 

[JSL]

some years ago I was involved with a twin pontoon 'float home' review. The least intrusive (quickfix) way to increase the freeboard (equal or more than 50% diameter) & meet local bylaws was to add a 3rd pontoon at center. Alternative: remove weight like hot tub, ceramic tile, brick fireplace, compensating trim/heel ballast, etc, etc.

 

[flyinwall]

Thank you all for your responses...
The reason for the replacement of the original pontoons is the fact that they are leaking and filling with water causing the houseboat to list down on the front port side.
Talking to the original builder is not possible as he is no longer contactable (by earthly means ...) the boat is almost 40 years old so it is time for some maintenance on the pontoons... i have had a quote for getting the pontoons foam filled but at the cost of Au$12-13,000 that is a bit prohibitive..
The reason i am thinking of the larger pontoons is so i can just get a standard 4'x8' sheet of 3mm aluminum rolled and have a mate weld them up for me (yes i know thats a lot of welding...) and only having 2 pontoons gives me better weight distribution for the fresh/grey/black water tanks as they will be central and not either side of the center pontoon.
I have also decided not to increase the length to 12m instead i will be making them 10.8m (9 sheets of aluminum long instead of 10).
I am aware that i might need to add support beams across the bottom on the boat when removing the center pontoon but the added weight of those will be offset by the removal of the weight of the center pontoon (i will be talking with one of the local metal fabrication places regarding this soon...

 

[flyinwall]

Can you confirm the following?
-at present there are three pontoons, aluminum, of 3600 mm in diameter and 10 m in length.
- you want to place 2 pontoons, aluminum, of 2800 mm in diameter and 12 m in length.
- what minimum freeboard are you obliged, or want, to have?

we have 3 pontoons that are approx 600mm diameter and i would like to replace them with 2 pontoons that are approx 800mm diameter