Yamaha 115 4 stroke engine when it is throttled up it immediately starts to lose power/

You might have a magnet issue(under the flywheel).. it happened to me.. one was loose..

If your 115 Yamaha SHO VMAX outboard engine is experiencing RPM fluctuations at speeds over 3500 RPM, it may be due to a few different factors. Here are some things to check:

1. Fuel supply: Make sure that the fuel supply to the engine is consistent and free from any debris or obstructions. Check the fuel filters, fuel lines, and fuel pump for any signs of damage or clogging.
2. Spark plugs: Check the spark plugs to make sure they are clean and functioning properly. If the spark plugs are worn or dirty, they may cause the engine to misfire at higher RPMs.
3. Throttle position sensor: The throttle position sensor (TPS) sends a signal to the engine control module (ECM) to adjust the fuel and air mixture. If the TPS is not functioning correctly, it may cause the engine to fluctuate at higher RPMs.
4. Air intake system: Make sure that the air intake system is clean and free from any debris or obstructions. Check the air filter and air intake hoses for any signs of damage or clogging.
5. ECM software updates: Check with your Yamaha dealer to see if there are any available software updates for the ECM that may improve the engine's performance.

If you are unable to diagnose and fix the issue on your own, it may be necessary to take the engine to a professional technician for further diagnosis and repair.

Sounds like it has a fuel restriction. Hook up a fuel pressure gauge on the vst tank on the motor to make sure you have 30-50 lbs of fuel pressure.

You can buy the repair manual here:
http://www.fish307.com/clymer-115-250-hp-two-stroke-outboard-jet-drives-1999-2002-b789/

We do not have the info you are asking for. Sorry.

no car stated, huge NPR truck no less.
no year stated
so no free book information on that engine,.
big diesel. 4HL1, no dash letter?
compression at spec.?
glow plugs work.,
filters clean. water in fuel,
does test fuel (spray'd) help? ???
injection problems
lack of startup air.(filter)


The 4HL1 is a common rail direct injection OHC 16V high-pressure fuel injection system diesel engine of 4.777 L capacity with electronic control system. Peak torque is 333 Nm, peak power is 140 PS (103 kW) at 3,000 rpm. Maximum torque is (34.0 kg m)'/1,500 rpm. Bore is 115 mm, stroke is 115 mm.
The 4HL1-N is a common rail direct injection OHC 16V high-pressure fuel injection system diesel engine of 4.777 L capacity with electronic control system. Peak torque is 333 Nm, peak power is 131 PS (96 kW) at 3,000 rpm. Maximum Torque is (34.0 kg m)'/1,500 rpm. Bore is 115 mm, stroke is 115 mm.
The 4HL1-TC is a common rail direct injection OHC 16 V turbocharged and intercooled high-pressure fuel injection system engine of 4.777 L capacity with electronic control system. Peak torque is 425 Nm, peak power is 160 PS (118 kW) at 2,700 rpm. Maximum torque is (43.3 kg m)'/1,500 rpm. Bore is 115 mm, stroke is 115 mm.
The 4HL1-TCS is a common rail direct injection OHC 16 V turbocharged and intercooled high-pressure fuel injection system diesel engine of 4.777 L capacity with electronic control system. Peak torque is 500 Nm, peak power is 179 PS (132 kW) at 2,700 rpm. Maximum torque is (51.0 kg m)'/1,500 rpm. Bore is 115 mm, stroke is 115 mm.

2003 Yamaha 115 4 Strokes Operation and Idle Demo ...

? 2:29
www.youtube.com/watch?v=sMmionreldM
Dec 29, 2012 - Uploaded by Peter Richards Engines for 1989 Larson boat with dual 115 Yamaha 4 StrokeEngines. ... Outboard Yamaha 150 HP DIRTY idle JETS, Motor will not idle .

more info needed but it sounds like fuel,maybe water like condensation

can you check that the fuel tank breather is not blocked.

Do you have spark? What about fuel? Have you tested anything?

this tells you there is a problem with cooling or lubrication ! what engine you got ?