When adding a 2nd level to a pontoon...

[VanDamage007]

Ok so I got a 8' by 24' pontoon boat and I am going to put a cabin on the back half of the boat, can I make a 2nd level on the boat and if I do, will it be tippy side to side? Is capsizing possible? Im concerned the boat might flip over. That would suck. So its an aluminum pontoon. I also was thinking of adding a water slide on it. Is this a good idea?

[alan white]

The second story is fine just so long as it is onlly a small deck without much beyond a chair or two and a railing. Even then I'd limit the "payload" to two people maximum.

Actually enclosing it with a second roof would be crazily unstable and such thoughts should be quickly dispensed with.
Slide? Just use common sense, I guess. That question may be a first here.

[Deadeye]

Just a guess here, but wouldn't windage be more of a problem than stability in a pontoon boat ?

[alan white]

Probably if it were 16 ft tall.

[VanDamage007]

Yeah its gonna have 7' walls on it. I was worried about the wind too, but Im only going on a small inland lake. I might take it our on Lake Huron a little too, but only a few times. Ill probally stick to one level tho and no slide. Dunno yet tho, as I have a slide just layin around....

[alan white]

Yeah, stick to one level. Even that's going to catch some wind--- and wind is everywhere. A boat can beat itself up against the dock too.
The slide, well you could do that.

[Deadeye]

I am going to put a cabin on the back half of the boat

Wouldn't gusts give you weather helm ?
With nothing to prevent leeway, docking might be a little tense on a windy day. Could you increase the size of the skeg on the outboard enough to balance it ?

[tom28571]

I operated a pontoon boat exactly like you describe some years ago as a race committee boat. The upper deck consisted of a deck and rail plus some signal masts. No real problem but think a fully housed second deck would be folly. Maneuvering was never a problem. Most pontoons are like a catamaran with lots of directional stability and don't blow around so much.

You have to be concerned about people gathering on one side, even at the dock. A pontoon dinner boat capsized within a few feet of their dock in calm weather on Lake Norman near here a few years ago. Not a pretty sight and more loss of life was prevented only by quick action of a rescue group on the dock at the time.

Small pontoon boats are good weather boats and should stay out of high winds and waves, even on lakes.

[alan white]

Pontoon boats carry weight pretty high up to begin with compared to regular boats. Windage isn't normally a problem but note that manufacturers don't seem to be selling full height cabin walls. Liability is surely a reason for this, as it would otherwise make for a good marketing idea.
Unfortunately for someone wanting to modify his pontoon boat, there aren't boats to copy that have a designer's stamp on them, unless they are very large (either pretty long or over-wide).
I don't even see high half-walls on them, though my experience may be limited.
I do think a small cabin of 6 x 8 ft would work on a good sized pontoon boat.
I'd put the cabin in the rear to prevent too much windage forward and limit the height to 6' 4" or so, and maybe even drop the floor a half a foot if there could still be a foot or so of free room under it so it wouldn't slap noisily all the time.
I think such a rig wouldn't be too affected by wind. It would step up forward onto the open deck and it could have a pair of berths port and starboard and a head centered far aft. There could be a galley flat to each side of the door forward (two 3 ft sections facing aft) with foot room under each side for the berths.
Others may think this is a bad idea but I think by limiting size and height as mentioned and keeping the helm outdoors, you could have a fair-weather upper deck as well. Again, it would have to be a large (24 ft) boat to begin with, something with some serious weight.

[VanDamage007]

Yeah I never meant a room upstairs, just a deck. I dont think Im gonna bother with it tho. Ill have plenty of room with one floor. Now dropping the floors an idea, lots of extra work tho. Maybe Ill stick to 6'6 floor to ceiling. That should be kinda ok. Im just planning on going out on nice days and not too far either, just wanna get out in the middle and chill!!!

[souljour2000]

hey..did ya ever get that pontoon boat cabin put together and be chillin out on that Michigan lake? Hmm..Summer in Michigan...must be nice if your not in the cities..always wanted to go check out upstate and the U.P. and the Canadian parts around that way...hmm... another summer is beginning to slip away..and I'm in Florida!...I mean for the rest of the country kinda...if I wanna go up north this summer I better get on my horse NOW and start ridin...Florida is a pretty interesting state but i grew up up north and well...there's nothing like a mountain lake in Virginia..in the Blue Ridge in the summer...you know what I mean...? Anyone know what I mean?