On-water test results. Real numbers. Every boat.
We collected independently published sea-trial results for the Granfort 370 GTX and each of its five key competitors. This page presents only figures from published magazine tests, BoatTEST.com reviews, and manufacturer sea-trial documentation — not estimated or derived numbers.
All published test results — head to head.
Every figure below comes from a published, named source. Where no independent test exists, we say so.
| Performance metric | Granfort 370 GTX | Sea Ray 320 OB | Sea Ray 370 OB | Beneteau GT36 OB | Schaefer 380 | Monterey 385SS |
|---|---|---|---|---|---|---|
| Dry weight (test basis) | 11,245 lb | ~14,566 lb | 21,008 lb | 15,901–16,036 lb | 19,675 lb | 16,000 lb |
| Engine config tested | 2×400 HP Mercury V10 | 2×350 HP Mercury V10 | 3×300 HP Mercury Verado | 2×350 HP outboard | No test published | 3×300 HP Yamaha F300 |
| Total HP (tested) | 800 HP | 700 HP | 900 HP | 700 HP | — | 900 HP |
| Top speed (WOT) | 50 mph (43.4 kn) | ~47–49 mph est. | 50.8 mph (44.1 kn) | 41.3 mph (35.9 kn) | No test data | 57 mph (49.5 kn) |
| Top speed source | Granfort sea trial | Estimate from specs | BoatTEST.com | Power Boating Canada | — | Boating Magazine |
| HP per lb (efficiency) | 1 HP : 14.1 lb | 1 HP : 20.8 lb | 1 HP : 23.3 lb | 1 HP : 22.9 lb | — | 1 HP : 17.8 lb |
| 0 to plane | 7.5 seconds | Not published | 5.7 seconds | Not published | No test data | 4.5 seconds |
| Best cruise speed | ~29 mph cruise | ~30 mph est. | 38.2 mph | 34 mph | No test data | ~36 mph |
| Cruise fuel burn | ~13.2 GPH | OB version not tested | 42.8 GPH @ 38.2 mph | 39 GPH @ 34 mph | No test data | Not published |
| Fuel efficiency (MPG) | ~2.2 MPG est. cruise | Not published (OB) | 0.9 MPG @ cruise | ~0.87 MPG @ cruise | No test data | Not published |
| Range at cruise | Calculated ~350+ nm | Not published (OB) | 201 miles (175 nm) | 103 nm (Boote-Mag) | No test data | Not published |
| Independent test review | Granfort.us sea trial · Marine Connection walkthrough | BoatTEST 2019 (sterndrive) · AU test (Coupe OB) | BoatTEST.com 2021 | Power Boating Canada · Boote-Magazin · Barche a Motore | No independent test published | Boating Magazine · boats.com · Lakeland Boating |
Every horsepower works harder in a lighter boat.
The chart below shows each boat's dry weight relative to the Granfort 370 GTX. Lighter = every HP works harder, fuel burn per mile drops, acceleration improves, and the boat feels more alive at every throttle position.
What each test actually recorded — with full source context.
Why Granfort reaches 50 mph on 800 HP while heavier competitors need 900–1,200 HP.
Power-to-weight ratio is the most important performance metric in outboard cruising. It determines how effectively each horsepower is used — and ultimately how efficiently the boat covers distance.
The Granfort 370 GTX carries 800 HP against approximately 11,245 lb of hull. That is 14.1 lb per HP — the best ratio in this comparison set. Every competitor carries significantly more weight per HP, requiring more engines and more fuel to achieve equivalent speed results.
Granfort 370 GTX
800 HP · 11,245 lb · The best power-to-weight ratio in this group. Reaches 50 mph with the least horsepower per pound of any boat tested.
Sea Ray Sundancer 370 OB
900 HP (3×300) · 21,008 lb · BoatTEST confirmed 50.8 mph — matching Granfort's speed but requiring 100 HP more on a hull nearly 10,000 lb heavier. Cruise fuel burn: 42.8 GPH vs Granfort's ~13.2 GPH.
Beneteau Gran Turismo 36 OB
700 HP (2×350) · 15,901–16,036 lb · Power Boating Canada recorded 41.3 mph — 8.7 mph slower than Granfort with 100 HP less on a ~4,800 lb heavier hull. Cruise burn: 39 GPH.
Monterey 385SS (900 HP std)
900 HP (3×300) · 16,000 lb · Boating Magazine recorded 57 mph — faster than Granfort, but with 100 HP more on a 4,755 lb heavier hull. Classified as a bowrider/super sport, not a cruiser.
Sea Ray Sundancer 320 OB
700 HP (2×350) · ~14,566 lb · Australian test of Coupe version recorded 33-knot cruise / 141 nm range. No full WOT test published for the standard open OB version — estimated 47–49 mph.
Schaefer 380
No published performance test available. At 19,675 lb displacement, any twin or triple outboard configuration faces a significant weight-per-HP challenge. BoatTEST listing suggests a future review is planned.
What performance tests measure — and what they don't.
Published sea trial data tells you three things reliably: top speed, acceleration to plane, and fuel burn at a specific RPM. What it does not tell you:
Rough water handling. A deeper deadrise (21° on the Sea Ray 320 and Monterey) will generally ride softer in offshore chop than the Granfort's 18° — but the Granfort's lighter weight partially compensates by requiring less power to maintain speed in the same conditions.
Dockside and low-speed behaviour. All boats in this comparison include Mercury or equivalent joystick docking. This equalises one of the historically challenging aspects of large outboard management.
Long-term fuel economy. The Granfort's dramatically lower fuel burn at cruise (~13.2 GPH vs 39–43 GPH for the heavier boats) reflects its lighter displacement. Over a full season of use, this difference compounds into thousands of dollars in fuel cost at equivalent distances covered.
Noise and vibration. Modern triple and twin outboard configurations from Mercury, Yamaha, and Suzuki are all remarkably quiet. The Granfort twin configuration and the Sea Ray triple tests both note comfortable conversation levels at cruise.
What the test data tells the buyer. Clearly.
The performance data confirms what the weight numbers predict: the Granfort 370 GTX reaches competitive top speed (50 mph) with the lowest horsepower and the lightest hull in the comparison. Its cruise fuel burn of approximately 13.2 GPH is dramatically lower than the heavier competitors' 39–43 GPH — meaning more miles per dollar on every trip.
The Sea Ray 370 OB matches Granfort's top speed at 50.8 mph — but requires 900 HP on a 21,008 lb hull to do it, burning 42.8 GPH at cruise versus Granfort's ~13.2 GPH. The Monterey 385SS goes faster (57 mph) but requires 900 HP on 16,000 lb and is a bowrider category, not a cruiser. The Beneteau GT36 OB tops out at 41.3 mph on 700 HP from 15,901–16,036 lb — the slowest result in the comparison, confirmed across three independent tests.
Granfort 370 GTX: granfortboats.us/granfort-370-gtx-sea-trial/ (published April 2025) — top speed 50 mph, planes 7.5s, 0–29 mph in 6.8s, ~13.2 GPH cruise. Marine Connection walkthrough (Jan 2025 YouTube). BoatTEST.com dry weight validation (11,245 lb).
Sea Ray Sundancer 320 OB: BoatTEST.com 2019 (sterndrive version — 44.7 mph top, 33 GPH @ 34.2 mph, 159-mile range). boatsales.com.au 2021 (Coupe OB with twin 350 HP Verados — 33-knot cruise, 133 L/h, 141 nm range). Note: no published WOT test for the standard open outboard version.
Sea Ray Sundancer 370 OB: BoatTEST.com full sea trial 2021 — empty weight 21,008 lb, test weight 22,947 lb, triple 300 HP Mercury Verado, 50.8 mph WOT @ 5,900 RPM, 5.7s to plane, 38.2 mph best cruise @ 42.8 GPH, 0.9 MPG, 201-mile range.
Beneteau Gran Turismo 36 OB: Power Boating Canada (2×300 HP Mercury — 41.3 mph WOT @ 5,700 RPM, 48 GPH WOT, 34 mph cruise @ 39 GPH). Boote-Magazin Germany (2×350 HP Suzuki — 36 knots top @ 5,650 RPM, 103 nm range). Barche a Motore Italy (2×350 HP Suzuki — 35 knots top, 199 L/h, 120 L/h @ 24.5 kn cruise). Boating Magazine (spec validation — 15,901 lb, 17° deadrise, 200 gal, 700 HP max).
Schaefer 380: No published independent performance test (May 2026). All figures from Schaefer published specifications only (SchaeferYachtsDirect.com, Schaefer Yachts USA, YACHT Solutions Canada). BoatTEST.com has the 380 listed for future review (boattest.com/boats/schaefer-yachts/380-2026).
Monterey 385SS / 385SE: Boating Magazine (385SE with triple Yamaha F300 300 HP — 57 mph WOT, ~4.5s to plane, LOA 37'0", 16,000 lb, 250 gal, 21° deadrise). boats.com review 2024 (50+ mph, deep-V handles chop well). Lakeland Boating (385SE with triple Mercury Verado 300 HP — 36 mph @ 4,500 RPM cruise). Top Notch Marine walkthrough (triple Mercury Verado 300 HP standard, 16,000 lb, 250 gal, 49 gal water). itBoat base price ~$562,000.
