Yamaha Outboard Problem

[STO-Becky]

Model F4MSH
Seriel 1092673 It is an 2008 model.

It starts fine and runs fine at low RPM. When you advance the throttle to full it it RPMs at half. We replaced the coil, coil wire, spark plug boot, checked the valve gap. It was all okay. Why would it be running at only half RPM at full throttle?

Becky

[robert graham]

Most likely carb needs cleaning...jets and passages are so small, they get plugged up with water/debris very easily. Good Luck!

[STO-Becky]

Thanks for the input. We actually already checked the Carburetor as well as all the filters. Becky

[robert graham]

Thanks for the input. We actually already checked the Carburetor as well as all the filters. Becky

The carb has to be removed, disassembled and cleaned....some of the jets are very small and have to be cleaned with fine wire, ultrasonic, carb cleaner, etc. Good Luck!

[99yam40]

How do you know the RPMs are only half?

Could be the device you are using to measure RPMS is not set properly

[casey1240]

Remove your cowling and watch your butterflies on your carb. They should open all the way (flush) when at full throttle. I've seen where the throttle cable can slip where it attaches to throttle handle and even though your at full throttle your carbs are not open all the way.

Also check that your oil pump is working. On my 50 hp, if the oil injection is interrupted than it will automatically go into safe mode. Same on cooling.