Tachometer

[Sidserv]

What tachometer will work with a 1973 Johnson 65Hp? My origional airguide is not going above 4K.

 

[metriccrescentwrench]

Re: Tachometer

Are you positive your tach is bad? A malfunctioning tach is often indicative of charging system problems, usually a bad rectifier.

 

[boobie]

Re: Tachometer

Put a volt meter across your battery and take a reading. Then run the mtr and see if your voltage climbs to about 14 volts or better. If it does your charging system is okay and your tach may be bad as it works off of the charging system.

 

[Barnacle_Bill]

Re: Tachometer

Did it use to work properly?

 

[Sidserv]

Re: Tachometer

The tach worked great a couple years ago. I did notice when I started the motor the last time when I was headed back to the dock and I got a message on the sonar about a low battery voltage. Could a battery that is weak cause the tack and motor to cut out? Once I stated the motor the warning went away. Could the battery be pulling too much of a draw on the system causing the motor to cut out and tach to not work?

 

[Barnacle_Bill]

Re: Tachometer

Test your rectifier. A bad diode in it will affect your tach.

 

[boobie]

Re: Tachometer

Agreed. Check your charging system out.

 

[Sidserv]

Re: Tachometer

Ok I Ohm'd out the rectifier and alternator. Both checked good. This was going step by step with the factory service manual. Going to dump the gas and start with fresh gas, change the battery to a new one and take it out and run it. Planning on checking the charge at the battery tomorrow when I get a chance to fire it in the can again.

 

[metriccrescentwrench]

Re: Tachometer

Could a battery that is weak cause the tack and motor to cut out? ..... Could the battery be pulling too much of a draw on the system causing the motor to cut out and tach to not work?

No, and no.

While a bad rectifier is a common cause of a malfunctioning tach, it's not the only cause. You could also have a bad stator, or it could just be a coincidence that you're battery is on it's last leg at the same time that your tach died. Since you have the factory manual, definitely go through all the steps to verify your entire charging system is functioning properly.

 

[Sidserv]

Re: Tachometer

I went ahead and took the boat out today. It ran great for most of the day and then things went bad again. I stated looking closer at the rectifier and noticed that the red wire had a broken casing and was arcing on the rectifier case. I was trying to get it to where I could put some tape to fix it and well the casing crumbled. Needless to say I ran home with my kicker motor. Not sure if that is the problem or not. Still can't get the motor to go over 4k while under load. I am pulling all the electrical system to check all the wires. I know it isn't the tach. With the motor in neutral I can rev it up and it will hit 5k without a problem.