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BF50 warning buzzer

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Dannbran

Member
Getting an intermittent buzzer when throttling up much past idle, green oil pressure light comes on, but if I try and continue throttling up the motor will shut itself down. It does crank back up but doesn’t want to go much past idle before that alarm goes off. I was thinking trim angle sensor but not sure now. Any help would be greatly appreciated.
 
Hi,

You should probably list a bit more info...

Year model?
Fuel injection?
Happens cold? After warm up? Both?

When was last water pump and or thermostat replacement?

Strong water tell tale?

Suddenly started doing this?

Gradually getting worse?

Anything you think is pertinent and might help someone help you.

Good luck.
 
Sure, it’s a 1998 so carbs not fuel injected. The green oil pressure light is on as soon as I start (this may be normal and I just never noticed it). The buzzer/alarm starts once I give it a little throttle, can idle along at 5-7 mph but past that and it starts chirping. Motor is peeing as it should and the water gets warm, but not scalding hot. I bought this boat about a year ago and was having problems with a cylinder not firing. I remember in the wiring panel there being one set of wires that were disconnected and I’m wondering if the guy I bought it off of had bypassed the trim angle sensor?
 
The green oil lamp being on is a GOOD thing.....and.....a Honda thing. When it's lit it means that minimum oil pressure is present. You're supposed to worry when it's NOT lit when the engine is running. They do that with many of their models so it's not part of your problem I wouldn't think.

You may be correct about the trim sensor but I don't know. Maybe you could try unplugging it and see if that makes a difference.

I have no experience with the '98 50hp. nor have I ever dealt with a trim angle sensor. My experience with Hondas is primarily with the twin cylinder models.....20hp and below.

Hopefully someone else here will offer suggestions about that.

I am surprised though that you don't mention a red overheat indicator. And, I wonder, could some of that disconnected wiring be for that?

Sorry I can't offer much. I don't have a wiring diagram to consult to try and help you sort this out.

I ask about the overheat alarm because there have been several posts here, for several different models, that describe similar intermittent warning buzzer activation along with power loss (guardian mode) and in several instances it turns out to be debris build-up inside the cooling system.

Not saying that's what is happening with yours but just offering it for consideration.
 
I found a PDF copy of an owners manual by googleing "Honda 50 hp outboard owners manual".

It has a wiring diagram and the trim angle sensor.wire colors are:

Yellow with blue stripe (Y/bu)

Light green with black stripe (Lg/bl)

Black (Bl)

The wierd thing is that it doesn't show a trim angle guage. Those wires all appear to go into the dash but not connect to anything. That makes me think it's an option.

I will try to see if I can understand how that works and get back to you.

It also shows a 3 lamp module or cluster for the dash...as I thought it might.

A no charge warning lamp
An overheat warning lamp
And the green oil pressure indicator lamp.

As it turns out, it's not much different than the warning system on the 20hp.

One thing you might try is to disconnect the red wire at the thermo switch (engine temp sensor) and try running the engine with it disconnected.

If the symptoms go away, it could simply be that the sensor is bad and sending a false overheat signal.

BUT....you need to use caution doing that because disconnecting the switch also disables the engine protection (guardian) system.
If for some reason the engine is actually overheating it won't de-power and protect itself.

So, doing that "test" should only be to get an idea of what might be going on to activate the system and buzzer.

Do it briefly for the information you might glean from doing so but do more checking to make DANG sure that you DON'T have any overheating taking place.
 
Trim angle will not do anything to the engine operation, it’s just to show you the angle of the boat in the water as far I know. I had that on my 99 130hp, removed the gauge and installed an hour meter since there is no way on this vintage of Honda to know hours.
 
I would bet on an overheat alarm causing your shutdown, check thermostat for corrosion, may need a good flush in a barrel, and or a complete water pump kit. My outboard is very sensitive to the overheating alarm, any small reduction in water pump flow will trigger the guardian mode and alarm.
 
I do want to be clear it is not a solid beep but a beep…beep…beep. I thought I had read somewhere that the sold beeep was the overheating alarm but may be mistaken.
 
So I disconnected the yellow with blue stripe wire in the box (same color that is on the trim switch) and took her out and no buzzer or limp mode.
 
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