Merc 150 voltage output

[gw204]

Hello everyone. I just joined the forums and am hoping you can help me resolve a sporadic problem I'm having with my outboard.<br /><br />The engine is a 1985 Mercury 150 Black Max. Since I installed a new Furuno fishfinder this year that reads battery voltage, it sometimes flashes "input voltage too high" and instructs me to power off the unit. At this point the motor is outputting at least 16.0 volts. I verified this reading w/ a voltmeter. It is my understanding that it should no be more that 14 or so. I just relocated the battery and installed NEW battery cables so I know all connections are clean and tight and the wires are in good shape. I replaced the rectifier on the engine after it was explained to me that it could be leaking AC voltage into the DC system and "fooling" the fishfinder, but the problem persists. What else should I check/replace? Thanks.<br /><br />Brian

 

[gw204]

Re: Merc 150 voltage output

Sorry, I forgot to mention that this only happens above 2000 rpm.

 

[aeronutt29]

Re: Merc 150 voltage output

Depending on how old the battery is, it may need to be replaced. Sometimes an old battery will output over 18 volts due to sulfate buildup on the internals. It won't hold that voltage under load, but since your motor is providing a charge there is no load. Try disconnecting the battery, charging it with an automatic battery charger, then testing the open circuit voltage. If it's above 14 you should consider a new battery. If it's WAY above 14 (like 16 - 20) you have definately found the problem. Maybe just use the old one for trolling motor power.

 

[gw204]

Re: Merc 150 voltage output

Thanks aeronutt, I'll give it a shot.

 

[ODDD1]

Re: Merc 150 voltage output

gw, what you are experiencing is normal...these charging systems will put out 16+v on a fully charged battery...was never a prob until the more fussy electronics showed up....turn something on to pull down the voltage, or a regulator can be added to limit voltage....

 

[gw204]

Re: Merc 150 voltage output

If the 16+ V is normal, should it be doing it 100% of the time or is the sporadic reading normal?<br /><br />What's the proper way to add a regulator?<br /><br />Thanks.