[SkiPro3]

I'm in the market for a pontoon boat. However, before I put the cart before the horse, or, in my case, the Ascent before the pontoon boat, I have a few questions;
The boat and trailer are 31' long total. (Boat is 25' long) They weigh together under 5000 lbs. Closer to 3500 pounds fully loaded. Tongue weight is under 500 pounds but can only guess at this time at around 400 pounds. While technically this is well under the max capacity, the trailer is very long with the dual axles sitting quite a ways back. I guess the boat is light until you hang a 150 horse power motor off the back. (Notice the waterline on the pontoon showing the front rides higher in the water than the rear because the rear has the heavy motor and fuel tanks) The puts the axles further back for the right load balance. I don't want to somehow end up having the tail wag the dog if you know what I mean. I'll be towing this to mountain lakes on well paved, but at least 20 miles of twisty road that climbs 3,000', starting at 2,000' and ending up above 5,000' at the lake. The trailer will have brakes and I will have the option of; surge brakes, drum on one axle or disc brakes both axles. I'm attaching a photo of a 25' pontoon boat on a 31' trailer for scale so you can see what I mean by axles rearward.
Any thoughts or suggestions, please reply.

 

[Robert.Mauro]

Less "tail wag the dog" with the axles all the way in the back. Less of it with tandem axles. A lot less wind resistance than a similar weight travel trailer, so that too will help. A little more wind turbulence, but probably not enough to really matter.

Hopefully our boat towing members will chime in.

 

[Titanrx8]

I tow a 17' with a heavy 4.3l Volvo I/O sitting behind the single axle. The axle assembly is attached to the frame's box-section rails with large u-bolts. It's been a long time since I adjusted the position of the axle further rearward but it is doable. Supported the frame on jack stands, loosened the u-bolts and rolled the assembly back and re-checked the balance. I did trial and error moving it a couple inches at a time. It was tedious but not that difficult.

 

[Merope]

Yeah. On the boat trailers I've had the axles were movable. I'd set it up for ~12% tongue weight which was under the vehicle's limit. The presence of a 450 lb outboard on the back will obviously make a very big difference in tongue load. I don't think the length will be an issue at all. The longer boat/trailers I've towed were all very stable.

 

[Titanrx8]

This just prompted me to look up the weight of my engine+out drive. 919lbs all sitting behind the axle. At least the 30 gallon tank is mostly over the axle.

I never got the tongue weight properly high enough because I'd run out of ramp if I moved the axle back any further. Ramps around here are soft muck beyond the concrete. You never want to go past the end.

 

[Merope]

^^^ yeah. Not as extreme in my case but I had a storage locker in the prow and I'd put heavy stuff up there. The anchor and chain was already there but I'd put my dive weights etc up there too. Since it was so far forward of the trailer axle and near the ball it was almost a one to one increase in tongue weight.

 

[Idaho Oak]

Take your corners wide.

 

[burgessms]

Brakes - Do they make electric brakes for submerged boat trailers ?
As to surge brakes on mountain downhill roads, won't they bottom out eventually ? I'd go for 4 disc over 2 drum any day.