I just bought a 1988 Formula 311. I think the brochure shows 7400 lb. It's got Big Blocks and a steel Manning trailer. With a hundred and fifty gallons worth of gas in 15 gallons of water what's my total gross weight? I'm trying to figure out what kind of truck I need at a minimum to be safe and legal to drive this boat. Thank you

At minimum a 3/4 ton but I'd go ahead and get a dually. Any of the modern f250, duramax, Cummins trucks can handle that boat. I have friends that fish with us towing 31 contenders with 6.2 gas burner Yukons. It works just drinks a ton of fuel. I'd reach for a 6.7 Cummins if it were me and the budget allowed.

gal water = 8.3 lbs 15 x 8.3 = 124.5 lbs
gal gas = 6.1 lbs 150 x 6.1 = 915 lbs
add in gear, food coolers = 400 lbs

7400 + 124.5 + 915 + 400 =8839.5

Some one would have to help figure difference between small block and big block weights. But looks easily at about 9500 lbs on a conservative guess. Now add in the trailer weight. looks like maybe 11,500 - 12,000.

Sound reasonable?

Any 3/4 ton truck will work just fine

My 303 weighed 10,200 on an aluminum trailer so you'll probably be around 11,500+.
Any 3/4 ton will be just fine.
Having said that, the guy that just bought my 303 towed it home with a newer F150 with factory air ride and he said it did just fine.

I want to try to be safe but also legal in case I get into an incident. So I'm estimating 11.5 to 12000.

Why not tow to a truck stop and weigh it on the CAT scales. 1st weigh is $11.00 and additional weighs on same day is $ 2.00 each.

I will probably just do that. I just assumed on this floor that would be enough information on like boats.
thanks to all, Tom

Like everyone is saying a 3/4 ton will handle it. I've been towing heavy long distance for over 13 years now. I love a 3/4 ton dodge with a 5.9. But once I got settled in a dually I love it. So much more stable. Less tire fatigue. So many winning factors.
Being as you will probably need this vehicle for daily commute and towing your boat, a single rear wheel may be best.

In later years formula revised the dry weight to 8k. Figure 2k in fuel, water, gear etc. 2k for steel or 1500 for aluminum trailer. 11500 on an aluminum trailer is a pretty good estimate.