Mercruiser alarm

[rrobinson3852]

2003 Formula PC27 with twin Mercruiser 350 MPI engines and Bravo III's.

I have a non-sticky alarm that only occurs when I exceed 3500 rpm. The alarm is the standard 2 beeps/1min interval, and it is dropped when the key is shut off and then restarted. It then will not re-occur until I exceed the 3500 threshold.

Merc manuals show this alarm as a "shift switch" alarm, and no code is thrown. Unfortunately, Bravo III does not have a shift switch. Have cleared all codes on both engines and the alarm returns. All connections have been checked and all sensor outputs are within tolerance.

Did not have the Rinda with me to check if there is a volatile code tossed when underway. Any suggestions as to what I may have missed?

Thanks, Randy

 

[dubs283]

Re: Mercruiser alarm

Unfortunately, Bravo III does not have a shift switch.

yes it does

it is an "in gear" switch that tells the ecm when the shifter is in the "in-gear" poistion

the ecm thnks the drive is in neutral when actually in gear and when you hit 3500 rpm it triggers the overspeed in neutral code

try swapping the switch with the other engine and see if the problem moves

 

[rrobinson3852]

Re: Mercruiser alarm

Thanks for the reply. Is there a code, or is it simply a volatile alarm? Will it show up on my Rinda meter when I have a chance to test it under load?

RR

 

[rrobinson3852]

Re: Mercruiser alarm

Update: Ran a simple continuity test on both switches. Starboard switch always on. Parts are ordered.

 

[rrobinson3852]

Re: Mercruiser alarm

Thanks for the insight. I replaced the switch and cleared all codes. Under sustained WOT, the alarm is silenced.
The information on this switch is poorly documented on factory publication and all aftermarket information sources that I found. My mechanic was unable to fix the problem for 2 years. I guess that to "fully understand....." you have to take control and do it yourself.

Thanks,

Randy
U.S.C.G. Captain