225 hp intermittent long alarm

I work for a department that has several boats running dual 225 hp outboards. We often get a long alarm while underway on one of the motors and that motor will drop to idle. Upon stopping and then restarting the motor, the problem goes away for hours and sometimes days. There is no noticeable change in performance or engine sound prior to the alarm. It does seem to be more prevalent at low to part throttle operation. Anyone have any ideas?

What lights are lighting up on the key switch panel? The green oil pressure light should be on. If the MIL light is on solid red, and no other lights are on, then it's a problem with the programmed fuel injection system, which could be any one of a host of things. Your next step is to pull fault codes off of the ECU's EPROM. It's a simple procedure using a paper clip. If you need instructions on how to do it, send me an email at [email protected].

None of our boats are equipped with warning lights. An 02 sensor will temporarily fix the issue, but not for long.

Well, now that is pretty interesting. How do you start the engines without a Honda key switch assembly?

The Honda key switch assembly will have either two lights on it, or four lights. The four-light system has a green oil pressure light, a red overheat light, a red alternator malfunction light, and a red "check engine" (Malfunction Indicator, or MIL) light.

If the replacement HO2 sensor temporarily fixes the problem, then you probably have engines that have the original exhaust tubes. Engines with serial numbers below BAGJ 1500325 or below BAHJ 1500022 all have the original exhaust tubes, which should be replaced IAW Honda Service Bulletin # 56.

Those tubes allow water mist to get way up into the exhaust tubes and destroy the HO2 sensor, which in turn will cause your engines to run too rich.