Speed varies 2003 Yamaha 225 4 strokes

[finaddict4]

Any suggestions? When running into a head sea, Rpm's remain steady, however speed can vary by 4 to 6 mph. Could a hub be slipping? or am I being paranoid. Problem does not seem to happen going with the current or in the calm intercoastal. Twin engines on the boat.Thanks.

[boats.net]

If rpm's are steady then probably wouldn't be a hub slipping or problem with engine. You can mark a line across prop washer and prop hub. If slipping mark wont stay aligned.

[Freddy]

Sounds like normal operation in a head sea. Keep in mind as you travel forward the water resistance will vary depending on the angle of the bow, height of the wave, and how much of your boat is past the wave. If rpm,s are steady the variance of speed is definately the sea conditions. You can minimize this by adjusting your speed, usually an increase, but it will cause a rougher ride.