Honda - BF200

First time posting.
I have read through many of the other threads and could not find a solution.
Serial Number - BAEJ1200019.

Situation:Boat and motor recently purchased at an auction.

Boat and motor had sat outside in the Pacifism Northwest for 4 years.

Honda mechanic went through the motor and replaced the water pump
Ran find on the muffs.

When in the lake at idle after about 4 - 5 minutes the alarm sounded - Short intermittent beeps.

When restarted and immediately taken up to cruising speed the alarm did not sound.

When then taken down to idle the alarm would sound after 4 or so minutes.
When taken back up to cruising speed the alarm would not stop beeping.

The boat had other issues and we took it to a boat mechanic, not a Honda mechanic, who has worked on my various boats for over 25 years.

When they ran it with the muffs on, no alarm.
When lake tested the alarm came on at idle after 4 or so minutes.

There has never been any sign of water in the separator so we replaced the whole unit, sensor and all. - no alarm with the muffs on.
Back to the lake, alarm sounded after 4 or so minutes.

The boat has voltage gauge (seems to be charging fine) and only a 2 light key switch indicator. Neither lights up when the alarm is sounding.

All research we have done indicates that when there is a short intermittent alarm, the only issue is water in the separator.

The mechanic has noted that the port side exhaust manifold seems extremely hot compared to the starboard side yet the overheating light does not come on,

Does anyone have any solutions or suggestion?

Thank you

Look at wires located at bottom of water indicator bowl. many times I found the insulation broken and the wires , shorted. The circut must be open. I would hope for it to be that easy, but I don't think so. There are as you know, 3 types of audio alarm. The only true way to resolve the issue is to have a tech and his honda diagnostic software. It will take him about 3 minutes to tell what bthe issue is.I believe that it will turn out to be a rich oxygen sensor. I didn't say Bad. I would see if the unit has nippon denso spark plugs and replace with NGK only. Next I would check the idle air solenoid next to the throttle butterfly. Remove and inspect screen and clean with carb and choke cleaner. Remove main air intake box on top of unit and inspect screen, remove debrisKeep safety in mind. Try the above and let us know how you are progressing. Thanks Martin

mcyama said:

Look at wires located at bottom of water indicator bowl. many times I found the insulation broken and the wires , shorted. The circut must be open. I would hope for it to be that easy, but I don't think so. There are as you know, 3 types of audio alarm. The only true way to resolve the issue is to have a tech and his honda diagnostic software. It will take him about 3 minutes to tell what bthe issue is.I believe that it will turn out to be a rich oxygen sensor. I didn't say Bad. I would see if the unit has nippon denso spark plugs and replace with NGK only. Next I would check the idle air solenoid next to the throttle butterfly. Remove and inspect screen and clean with carb and choke cleaner. Remove main air intake box on top of unit and inspect screen, remove debrisKeep safety in mind. Try the above and let us know how you are progressing. Thanks Martin

Click to expand...

Thank you !!
Will give that a whirl on Monday

You have a faulty oxygen sensor

Ditto on Martin's advice. The very short intermittent alarm says there is water in the onboard fuel/water seperator. If it is not present, then either the float is getting stuck in the up position, the sensor is bad, or the wires are shorting. The fact that it only happens on water, at idle, may indicate that there is a short due to changes in the attitude of the boat. That could be a wire, or the float sensor itself. If you are on the water, simply unplug the wire coming from bottom of the on board fuel/water seperator. If the problem goes away, then you need to test and repair or replace the fuel/water seperator. (I know you said you replaced it, but test it anyway.) It's easy to check the sensor - disconnect the plug of the wire coming out of the bottom of the bowl, remove and empty the bowl, and check the continuity on the pins of the wire to the sensor. If the float is down, there should be no continuity. Turn it upside down or gently push the float up so the float is at the top of the bowl, and you should get continuity. Test how far the float needs to travel up toward the top before you get continuity. It should be about half way.

If none of that works, then follow the wires from the plug to the ECM. Unplug the large connector from the ecm and clean the connectors.

All of the above is premised on the fact that you are getting a very short intermittent alarm - maybe two ro three beeps per second. If it is a longer intermittent alarm, one per second, then you have an entirely different problem. The first suspect would be the O2 sensor, as Martin said. Follow the procedure he gave you, above.

As for the difference in heat between the heads. Use a heat sensor gun and test under load. This engine does not get to full temperature until you run it awhile under load. The nominal temperature on the heads while cruising should be about 160 F. However, I have noted that on this engine, for some strange reason, while cruising, the starboard side runs about 15 to 20 degrees cooler than the port side. If either head is getting much above 160 F, then that indicates that something is clogged up inside the cooling system. Start by back flushing the engine from the t-stat openings.