Jet ski/Boat trailer attachment

Going on a boating trip in WI next week and want to bring both my 82SN and also my 87 Kawasaki Stand up. Unfortunately my buddy sold his pickup which I used last year by putting the ski in the truck bed and towing the trailer. So I came up with a design to haul both using my 2010 4Runner

Specs:
Vehicle Towing limits: 5000lb/ 500lb Tongue Weight (TW)
Boat Estimated weight: 2600lb
Boat with trailer estimated weight: 3550lb
Estimated jet ski weight: 250 lb

I wanted a removable trailer attachment that would allow me to tow the boat & ski:
1. Without going over my total tow capacity
2. Without exceeding my TW capacity
3. While maintaining 8-15% TW/total weight distribution
4. With the ability to still tow the boat without the ski installed

I borrowed a 600lb scale from work to measure my current TW (375lb), and from that measurement and estimated boat/trailer weight I could estimate the boat center of gravity (CG) distance from the axle.

I would need to extend the tongue to make room for the jet ski, but also room to turn my vehicle, and open the hatch.

Putting the jet ski on the front of the trailer (375lb +250lb) would overload my TW capacity, so I would need to shift the boat rearward by moving the bowstop. The combination of extending the tongue and shifting the boat rearward would give me some sweet spot to meet my criteria.

- Shifting the boat too far rearward might be fine for towing with the jet ski, but if it's not on the trailer when I'm only towing the boat, my TW distribution could be well below a stable %
- Shifting the boat to little rearward and I could get very close or even exceed my TW limit when the jet ski is installed

Using the variables of tongue extension length and new bow stop distance I was able to determine:
- Moving the boat back 2" is ~25lb off the TW
- Extending the tongue every 6" is ~10 lbs of the TW

I decided on a max extension of 26" and moving the bow stop back 7". With this setup I estimate jet ski loaded TW to be about 450lb (>10%) and my unloaded TW distribution with the extension all the way in, to be about 7.5%.

The jet ski will be ratchet strapped to the supports and I'm going to remeasure the TW once everything is installed.

Skids made from carpeted 2x4's
Supports made from welded 3/16" Steel plates (CNC plasma cutter)
Extension held by one 5/8" hitch pin and one 5/8" bolt

CAD mockup


Measuring Tongue Weight


Painted and Installed


Jet Ski resting on Skids

Nice setup.

That's really slick. Nice work.