Pontoon conversion motor mounting

Hi guys
I recently bought a 16' 86 sweetwater pontoon and i am considering turning it into a tritoon. A few issues I have are finding a correct length center toon, and deciding whether lifting strikes would be beneficial for just the center log.

My thought is buy a longer middle log and mount it the in line with the front toons, then hanging the rest of the long pontoon off the back, effectively pushing the transom back 1 or 2 feet. I'm worried about stability and thrust, but I like this idea just need someone to help me figure out whether this will be a safe boat.

Thank you

 

Welcome to the Forum Jscan.

I tried looking online for a 1986 16' Sweetwater boat, but the closest I got was this 18' version -
1986 Sweetwater 18 UP1364 | American Marine & Motorsports https://www.americanmarina.com/Pre-Owned-Inventory-1986-Sweetwater-Boat-18-Shawano-Wisconsin-4849098

Why do you want to add a centre hull in the first place? Are you worried that you will not have enough reserve buoyancy for the anticipated load that you will carry?
That extra hull will give you extra buoyancy, but it will also give you a lot of extra resistance, especially if you get wave interference effects between the hulls.

How much power does your engine have? Is this enough for your desired speed 'as is', or will you have to get a 'new' bigger engine?

 

I’m also curious as to why you need to add a pontoon?
A haphazard guess tells me you want to add a bigger motor?
You’ll need to make the boat wider to add a center pontoon, as mentioned above, wave interference.
Better to look for a boat that actually ticks all the boxes.

 

The specs for the Sweetwater were not included in the link above. Most pontoon and tritoon boats are close to 8 feet wide, plus or minus, due to towing restrictions.
There are many tritoons around with 8 foot beams. plus or minus

Strakes provide additional lift as the round bottom hull shape does not lend itself for efficient planing (efficiency in this comment can be defined as lift or speed for horsepower used or even fuel consumption difference between 2 (pontoon) rounded hulls with an 18 inch width (diameter) compared to 2 flat bottom 18 inch wide planing surfaces.

Most pontoon boat manufacturer now, planing variety, utilize planing strakes as it improves efficiency.

The main reason for round pontoons is that it is cheaper to build than say flat bottom or moderate V hull bottom profiles. Rolling the profile allows a thin aluminum skin with the resultant beam being quite stiff/ strong for its weight and
cost.
The addition of lift strakes are cheaper to install than trying to stiffen flat aluminum sheets with internal stringers etc.