Yanmar 1GM will not go over 2700 RPM. Today against the wind and tide my Ericson 26 was not moving – I pushed the gas lever to the max (Wide Open Throttle) and the motor would not go over 2700 RPM.
In fact, the motor feels a bit sluggish in general as if it has no power. I have to say the bottom of the boat is pretty dirty and the wind was 12-18 knots. I have arranged to have a diver clean the bottom to see how different the motor performs .
The plate on the engine says 3400rpm delivering 6.5hp.
There were some great replies to this question. Some additional tests were suggested, such as checking the WOT speed when the transmission was not engaged. When this was tested, the engine ran to 3200 in neutral so all were agreed that this was a dirty bottom / barnacled propellor problem.
Lastly, it was suggested that the OP checks for any exhaust smoke that might indicate issues like not getting enough air and possibly clean his fuel and air filters.