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what is the full weight of the boat? Assume boat dry weight+ full fuel tank+trailer+gear. Also pay attention to where you are getting the dry weight of the boat as most manufacturers are posting dry hull weight which means you would have to add the weight of the engine(s) too. For safety you should add a 10% safety margin to your figure to get your total potential tow weight.
My hitch is rated for 10k which is way more than i should ever tow so a 5k hitch is smallish. I would upgrade the hitch.
My boat is a 20' bay boat and only running around 5k lbs maxed out. I also have surge brakes. These are a separate closed hydraulic brake system for just the trailer. Most boats dont use electric brakes as it just not a good idea being as the brakes get submerged at every launch. There is a sliding collar on your trailer that slides forward as your tow vehicle slows down and the trailer pushes forward against your truck. when it slides forward is activates the trailer brakes creating extra braking power for you. works okay but not near as nice and linear as electric brakes with controller ( not an option for a boat owner).
As for the weight on back end of truck I am looking for a set of helper/lift springs to help level the look of my truck and the prevent so much sag when towing. So for your heavier boat I would say helper springs are a must but I would probably opt for bags for more adjustability.
hope this helps you some.
I've been pulling my 20.5 moomba and a 21.5 mastercraft boats for almost 10 years no problem. They are both on single axle trailers with onlt surge breaks. I've also pulled many 24 ft boats across the states and had no problems. All stock suspension except lowering kit.
i remember using a new V8 5.7/5.8 Toyota tundra and i was backing-up HIll with the boat and the transmission Ligth turn on because it was getting hot.. imaging my older Denali. darn. so just to be in a safe side. i will install a COOLOR for the tranny and a FAN for it too.
In case anyone is interested in the "official" maximum trailer weights ratings from GM for OBS trucks (out of my 1999 owners manual):
4WD Tahoe with 3.42 gears, 5500 pounds
4WD Tahoe with 3.73 gears, 6500 pounds
2WD Tahoe with 3.08 gears, 5000 pounds
2WD Tahoe with 3.42 gears, 6000 pounds
2WD Tahoe with 3.73 gears, 7000 pounds
That's based on a driver and one passenger, no extra gear or people in the tow vehicle. Add anything more, subtract that weight.
If you have tires that are larger than stock for overall diameter, you're losing tow capacity as you're effectively giving your truck a lower numerical gear ratio.
P245/75-16's are what came standard on my Tahoe with 3.42 gears. Those tires are nominally 30.5" tall. I'm now running P265/70-17's which are 1.25" taller, so my effective gearing is probably closer to 3.08...my towing capacity is probably down around 4500 pounds.