I have a 40hp four stroke about 6 years old. It has sailed about 100 hours. The motor strarts and is running fine to about 2000 rpm. Between rpm 2000 and 3000 the engine is running badly. I'll be grateful for a piece of good advice.

Greg, if you are puzzled about changing spark plugs.. Please take this to a shop somewhere.

what engine ?

I have a problem with my 2 stroke 20hp mercury 1989,when I run 10-90% throttle it's works fine but when in 100% its only runs in 90% and doesn't sound normal like it's not burning right.

My outboard motor is old and used.When I went to run it for the first time everything worked except when I went to put it in forward gear the boat went slowly but when I gave it more gas the engine just reved up but the boat wasn't going any faster.The motor is 40hp gale model.I think because it is bought used the prop is not the right one and it seems like it's slipping as I go faster.
I would appreciate any feedback on this problem.

Thax, Don

Model: Honda CBR 600 F4 Year: 2000 Category: Sport Engine and transmission Displacement: 599.00 ccm (36.55 cubic inches) Engine type: 599cc, liquid-cooled, inline, four-cylinder, DOHC, four valves per cylinder Stroke: 4 Bore x Stroke: 67mm X 42.5mm Carburetion: Four 36.5 mm slanted flat-side CV Compression Ratio: 12.0:1 Power: 110.00 HP (80.3 kW)) @ 12500 RPM Torque: 68.00 Nm (6.9 kgf-m or 50.2 ft.lbs) @ 10500 RPM Starter: Electric (Digital transistorized, with 3D mapping) Cooling system: Liquid Gearbox: 6-speed Transmission type
final drive: #525 O-ring sealed chain Physical measures Dry weight: 170.0 kg (374.8 pounds) Seat height: 810 mm (31.9 inches) Wheelbase: 1,395 mm (54.9 inches) Chassis and dimensions Front brakes: 296mm dual disc with four-piston calipers Rear brakes: 220mm single disc Tires Front tires: 120/70 ZR-17 radial Rear tires: 180/55-ZR-17 radial Speed and acceleration Quarter Mile Time: 11.00 seconds @ 124.65mph (199.44km/h) Top speed: 260.0 km/h (161.6 mph) Power/weight ratio: 0.6471 HP/kg Other specifications Fuel capacity: 18.00 litres (4.76 gallons) including 0.8 gal. Reserve Color options: Blue/red, black/yellow, black/dark gray

Mate.If its running for an hour before you have trouble,it may not be the motor.What is the motor or on????Sailing boat? tender?Fuel delivery is the main thing I would look at.Its a strange problem.Water in the tank?Sorry.Hope this helps

General information Model: Suzuki GSX 750 F Year: 1991 Category: Sport touring Rating: 66.2 out of 100. Show full rating and compare with other bikes Safety: See our safety campaign with the high safety rated bikes in this category. Engine and transmission Displacement: 748.00 ccm (45.64 cubic inches) Engine type: In-line four Stroke: 4 Power: 106.00 HP (77.4 kW)) @ 10500 RPM Compression: 10.9:1 Bore x stroke: 73.0 x 44.7 mm (2.9 x 1.8 inches) Valves per cylinder: 4 Fuel control: DOHC Cooling system: Air Gearbox: 6-speed Transmission type
final drive: Chain Physical measures

Sound like the fuel pump is not keeping up with the engine's demand. Check it out. Good luck. Hope this helps.

should cost less than $100 at a FORD DEALER. mine cost $65 four years ago.