Mercury 250 HP EFI Warning Horn Constant

[phoenix-Bangui]

I'm just at the front side of troubleshooting this, my Motor currently does not start and the warning horn has a steady beep every two seconds. Would like to get the basic on the horn first.

1. The steady beep indicates an overheat condition, is this connected strait to the thermostate or does it run through the ECU?

2. Does the thermostate fail to the open or closed position, meaning could I troubleshoot this by jumpering or disconnecting?

3. Does an overheat create a lock-out condition with the ECU so you cant start?

I just got the colored wiring diagram this morning on PDF so I will be digging more tonight, but these three questions answered should get me started. I will be checking for spark and verify that the horn is not low oil condition. Both oil tanks are full and again it's a steady non stop beep (every 2 seconds) and what I read 4 beeps is oil.

 

[IGIFF]

Re: Mercury 250 HP EFI Warning Horn Constant

This is a low voltage alarm,check your battery condition first.

 

[sschefer]

Re: Mercury 250 HP EFI Warning Horn Constant

This is a low voltage alarm,check your battery condition first.

Dang funny, just ran into this yesterday. Seems the ECU's on these buggers want juice all the time and will drain the battery just sitting. I put a battery switch in the guy's boat and hopefully that cured it. He still has to remember to switch it off.

 

[phoenix-Bangui]

Re: Mercury 250 HP EFI Warning Horn Constant

I think Both you guys are on the right track, I was thinking the same direction. Replaced the battery with new last night (still beeping). I bought a new multi battery switch about a year ago and never installed it, good advice (things to do this week). I had one of those switches on my last boat and it made things much easier. I also changed out the ECU still beeping. I think it may have been an overheat, do ya know of any way to isolate that?

 

[sschefer]

Re: Mercury 250 HP EFI Warning Horn Constant

I think Both you guys are on the right track, I was thinking the same direction. Replaced the battery with new last night (still beeping). I bought a new multi battery switch about a year ago and never installed it, good advice (things to do this week). I had one of those switches on my last boat and it made things much easier. I also changed out the ECU still beeping. I think it may have been an overheat, do ya know of any way to isolate that?

If it's a steady beep that won't quit then it might be the temp switch. I'm not sure if your ECU is capable of storing error codes but if it is, that is what you should look at next.

 

[phoenix-Bangui]

Re: Mercury 250 HP EFI Warning Horn Constant

Does the temp switch fail to the open or closed. How best to test?