Houseboat swim deck

I'm new to this so please excuse me if my terminology is not correct. I have bought my first boat and I guess you could say it's my midlife crisis toy even though it's for my family. I hope this is the correct place to post this question...

I have a 1997 boatel 50' houseboat on a fresh water lake. I had a 8 foot swim deck attached on the stern for the kids. I want to have two jetskis loaded on the swim deck and have the loading and unloading issue solved. My question is how do I figure how much bouyancy I need to compensate in the back? The jet skis will weight in at 680 pounds each, about 500 pounds worth of metal to build the swim deck and support the weight for a total of 1860 pounds. I currently have about 10240 (X 2) pounds of force with my pontoons (part that is in the water) plus or minus the angled front and back portions. I can do the calculations but I'm not confident with where to add the bouyancy.

We have played with the idea of building a single pontoon in the center of the swim deck. Not sure if that is the best idea. I'm not really worried about how it effects the steering since I will not be moving it much unless it would be unsafe.

Sorry my question is so long and please be gentle with my newbie question. Like I said, this is my first boat and an excited to spend time with my family at the lake!

 

One cubic foot of water weighs aproximately 62.4lb. If you house boat is on two pontoons, extending them would be the easiest solution. The submerged volume multiplied by 62.4, should equal the 1860 lb plus the weight of the extensions.

 

I put an outboard on the frame of a surfcat. It was OK until I tried to steer because the outboard was not at the rear of the hulls, instead of turning it went sideways. I realised than that the hulls behind the prop have to push sideways through the water.

I guess that is why rudders are at the rear of a vessel.

So, yes I think a pontoon extending from the rear of your house boat will effect the steering.

If you could articulate the swim platform so it works like a trailer on the back of a car or extend the steering and put the rudders on the back of the swim platform.

Of course the buoyancy is what Gonzo said, I think, we're metric here.

 

You might just tow them around instead of loading them on the swim platform, maybe designing something to keep them sort of corralled to the swim platform while letting them float and support their own weight.

Durango, right close to the Swiss Alps of America, it's beautiful there.

 

Thanks for the ideas! Samsam- it is beautiful here! I'm very lucky to raise a family here!

I need to keep the jetskis on the houseboat so I don't have to take them to and from the house! It will mainly stay on the mooring ball and a few trips out a year.

The houseboat has twin 60 hp motors on the back that's why I was thinking of a 6' pontoon in the middle of the swim deck could work? If I put two pontoons behind each of the motors I think it would effect the steering more?

Calculating the volume needed in the water for the proper lift is easy. I'm just not sure where to put it so it will give the proper lift and not push the front end down when I unload the jetskis. If I made it swivel I would imagine it would have a lot of wear and tear at the hinge point?

I feel like such a newbie, but I'm determined to figure the marine thing out! Love it every time I'm out there, just need more time and experience.

 

If you have two motors, you can steer with the shifters. Put one in reverse, and the boat will turn on its own length.

 

Very true. So you think one pontoon in the middle of the swim deck would work? Do you think having enough buoyancy to compensate for the weight will still work after the jet skis have been unloaded and not make it nose dive?

 

Since they are independent from the hulls, you can flood them with water to compensate for the weight.

 

Sounds complicated with lots of wires and pumps?