How it works
Everything that sits on the trailer, plus the trailer itself, is what your vehicle pulls:
Fuel weight = gallons × 6.1 lb (gasoline) or × 7.1 lb (diesel)
Boat package = boat + engine + fuel + water + gear
Total towing weight = boat package + empty trailer
If you enter the trailer’s GVWR, the total is checked against it (90% or more is at the limit). If you enter your vehicle’s towing capacity, it is checked against the 80% comfort rule. The suggested tongue weight uses the 5–10% range common for boat trailers.
Worked example
A 2,800 lb bowrider with a 500 lb outboard, 50 gallons of gasoline, 300 lb of gear and batteries, on a 900 lb trailer rated 5,200 lb GVWR.
- Fuel: 50 × 6.1 = 305 lb
- Boat package: 2,800 + 500 + 305 + 300 = 3,905 lb
- Total towing weight: 3,905 + 900 = 4,805 lb, 92% of the trailer’s GVWR.
- Suggested tongue weight: 240 to 481 lb.
The brochure said 2,800 lb. The real towing weight is 72% higher.
Boat fuel weight chart
| Fuel | Liters | Gasoline | Diesel |
|---|---|---|---|
| 10 gal | 38 L | 61 lb (28 kg) | 71 lb (32 kg) |
| 20 gal | 76 L | 122 lb (55 kg) | 142 lb (64 kg) |
| 30 gal | 114 L | 183 lb (83 kg) | 213 lb (97 kg) |
| 50 gal | 189 L | 305 lb (138 kg) | 355 lb (161 kg) |
| 75 gal | 284 L | 458 lb (208 kg) | 533 lb (242 kg) |
| 100 gal | 379 L | 610 lb (277 kg) | 710 lb (322 kg) |
| 150 gal | 568 L | 915 lb (415 kg) | 1,065 lb (483 kg) |
| 200 gal | 757 L | 1,220 lb (553 kg) | 1,420 lb (644 kg) |
What to include in gear weight
- Batteries: 40 to 75 lb each for marine lead-acid, less for lithium
- Trolling motor, anchor and chain, fenders and lines
- Life jackets, coolers, fishing tackle, skis and tubes
- Bimini top, covers, electronics and any aftermarket tower
- Water in livewells, ballast tanks and bilge (8.34 lb per gallon)
Wake boats with factory ballast can carry thousands of pounds of water. Drain ballast before towing. Then check the trailer tires with the trailer tire load calculator and your hitch with thehitch class calculator.
Common mistakes
- Using only the hull weight. Motor, fuel and gear often add 1,000 lb or more.
- Forgetting the trailer. Aluminum and steel boat trailers weigh several hundred to a few thousand pounds.
- Confusing trailer capacity and GVWR. Some trailers list load capacity (boat only); GVWR includes the trailer.
- Towing with water in the boat. Rain and bilge water add weight quickly.