DF300AP RMP Fluctuations??

[redlowrey]

I tend to go offshore only on calm days. It happens to me on flat calm water as well as rough seas. Since it is easier to feel on calm water, I notice it more. I want to cross to the Bahamas but until I understand the issue, I do not have a whole lot of confidence.

''''''''It sounds like your 02 sensor is lazy, if the rpm is dropping a couple of hundred rev's then back up while the sea is flat, and getting no interference from swell wind and current, the switch rate of the sensor could be too slow.
When you are in lean cruise, the ecm is switching the pulse width on the injectors from rich to lean on information from the 02 sensor to keep the fuel in stoich 14.7 to 1, if the sensor switch rate is too slow, it will actually drop the rpm slightly when lean, then rise when it goes rich, the sensor produces a voltage between .1 and .9 of a volt, the switch rate has to be fast.

Any engine using electronic throttle control, and say the shift position leever was set at a voltage corresponding to 4500 rpm and you hit a wave and the rpm dropped, the throttle would automatically open to retain that rpm level again, in rough seas that is going to happen all the time, up and down on the throttle. You will have to go back to Suzuki and have a sea trial where they can hook up a scan tool and watch live data on your 02 sensor switch rate, make sure that there is no voltage change on the shift position leever, making the throttle open and close out of sinc.