2005 Johnson 40HP (DF40 Suzuki) Continuous Alarm Horn

[xZapx]

I can't seem to find a scenario that is similar to mine when doing a search, so I figured I'd ask around. A year or two ago, we had an issue with the alarm horn where it would continuously beep at low volume during operation. When starting the boat, it would sound briefly at high volume (the normal power-up test) but then drop to a drone in the background. The tachometer lights all come on and disappear as expected. No codes, no error lights, and no operational problems when the engine is running. This occurs from a cold start and doesn't go away. The water stream from the pump is healthy and not of an elevated temperature. We've never encountered performance issues, limp mode, or any other error beeps as I've read about in other threads.

When I originally inspected the horn, the potting compound had some damage and so I figured maybe it wouldn't hurt to replace it, and the problem seemed to go away, at least for the most part. Fast-forward to the present - we just put the boat in for the season, and the horn is doing the exact same thing as a few years ago. The wiring harness going to the horn appears to be in satisfactory condition, without any visible damage.

For reference, this scenario is occurring on a 20' Suncruiser pontoon, originally equipped with an Evinrude outboard. Not sure if it is relevant, but the key/switch/throttle control unit is the boat's original OMC unit.

My first instinct is that this is caused by a bad ground somewhere. When I've done repairs in the past, I was less than impressed with some of the general wiring on the boat, as it looks like someone decided to use wire nuts to tie things together inside the console. Certainly, there has to be a better way - I suspect the Johnson has a harness of its own, but while I'm asking for advice, is there a standard normally employed on boats such as this for wiring junctions such as common +12V and ground (terminal strips, star ground points, etc.)?

Any insight is greatly appreciated!

 

[xZapx]

As an update, the grounds were re-worked with a proper terminal bar and some wiring to the battery was also re-worked due to corrosion. The noise is better, but on occasion it still surfaces at a much lower volume. Just curious if this is somehow normal, or if there might be another explanation.

 

[jakedaawg]

Horn has three wires right, purple, tan, and blk? Do you have a system check guage? Any lights on it? Binnacle controls or sidemount?

 

[xZapx]

The alarm horn actually has two wires, purple and brown/blue - It is part number 176361.

There is a system check as part of the tachometer, the lights come on as normal in the start up sequence, but don't stay on or flash any codes. Binnacle mount control.

 

[jakedaawg]

The easiest way to start is to plug in a known good system check guage as a test tool and see if it solves the problem, they go bad often. I keep one in the tool box. I realize this is not an option for a DIY.

It's likely one of two issues. 1 being bad system check guage. The other is stray voltage getting to the brown with a stripe wire through a short or a partly failed sensor. I suppose it could also get there through induction if the wire were coiled around something but I seriously doubt that's possible in the real world...

This diagnosis gets tricky. Too tricky for me to talk someone through over the internet.

Sorry, I mean this sincerely.

 

[xZapx]

Thanks for the follow up information. I'm not sure if it could be related, but more recently we are having another problem now. When you mentioned partially failed sensor, I got to thinking this could be related. I've tweaked the idle via the throttle cables to ensure it is set at the proper level, but there are some cold starting problems occurring regardless. The fuel line, low pressure fuel filter, and spark plugs have been changed recently to no avail. More often than not, the engine will turn over, but either stall or run for a little while and stall. On occasion, it will start successfully.

The odd part about this issue, is that putting the throttle in neutral and at a higher RPM seems to generally allow it to start and once the engine has run for a short period this way, it will idle smoothly. It will reach WOT properly, and runs great out on the lake as it always had. If the engine is shut off, it restarts just fine when warm. So it seems like something is off when the engine is cold. I've worked on many cars in the past, given that this is a 4stroke is there a cold loop mode and does that point to anything that may be causing this? The boat started reliably until this year, and it has only required routine maintenance (plugs, oil/filter, lower unit lubricant).

I've pondered buying the proper cable and software to dig into things further, if that would be helpful. But if anyone has any further or if I should post this in a new thread, I'm all ears. Thanks for all of the help!

 

[jakedaawg]

You need to test the IAC valve.

idle is set by a procedure with the idle bypass screw. You pinch off the IAC valve hose and use the screw not the cable ends.

a manual really helps.

you could also clean the throttle body, silencer, idle air bypass, IAC valve, and associated hoses.

this wont help the horn problem but it will be a start to diagnosing your idle issues.

Many times, a motor that fails to go 8nto high idle at start up has an IAC valve issue. Could also be he CTP.

 

[jakedaawg]

Upon further reflection...

if you have messed with the throttle linkage it's possible your ctp switch never turns on as the throttle will not be fully closed.

you need a manual, a lot of that stuff was factory set and not meant to be changed.

 

[xZapx]

Thanks so much for the helpful reply! I do have a service manual, and I will start by checking the IAC and adjusting the idle that way. Do you recommend a specific brand/type of cleaner? One thing I forgot to mention earlier is that sometimes the engine will idle higher than at other times. I suppose the IAC could be malfunctioning if this is the case.

Another question - I do recall seeing in the manual that 100% gasoline is preferred, but 10% Ethanol is acceptable. I know that this was critical for 2stroke engines in the past, but I've heard mixed opinions for the 4stroke. Are there major detriments to running the blend with this engine? On the note of fuel, do you have an opinion on using fuel injector cleaner?

Thanks again!

 

[jakedaawg]

Evinrude 2+4 late in season, evinrude fuel conditioner early in season, straight fuel rest of the time. Period. Others will have other wrong opinions. Now we will have another fuel thread. Maybe I should delete.

carb cleaner works for cleaning throttle body passage and plate and bore. Soap and water and compressed air for rubber hoses and silencer.

 

[xZapx]

Oops, didn't see your second post. Just to be clear, I adjusted the linkage cable where it enters the back of the motor and connects to the binnacle mount control using the screw mechanism that is part of the cable. I haven't adjusted anything underneath the engine cover. I actually did this after there was already a starting problem to see if it would help.