97 225 oceanpro cannot get tach to work

[oldwood]

Just purchased a Mako with a 97 225 Evinrude, it has the Modular Wiring System, the VRO has been disabled, the system check lights work, cannot get the tach to work, have replaced the tach and the rectifier/regulator,
does the VRO have anything to do with the tach signal?
What do I have to do to have a working tach with this system?

 

[Seasport]

Re: 97 225 oceanpro cannot get tach to work

No the VRO doesn't have anything to do with the tach. Is your battery charging? If not you may have a problem with the stator windings rather than the rectifier/regulator. Best to do some testing before replacing parts.

You can test the stator winding with a multimeter set to ohms. Disconnect the rectifier/regulator and measure the resistance between the yellow and yellow/gray wires. Should be very small (less than 1 ohm). If you have infinite resistance then you have an open circuit and the tach and charging circuit won't work. Also there shouldn't be any connection between either of these wires and ground.

Otherwise you might have a problem with your wiring or possibly the wiring conections at your tach,.

 

[oldwood]

Re: 97 225 oceanpro cannot get tach to work

No the VRO doesn't have anything to do with the tach. Is your battery charging? If not you may have a problem with the stator windings rather than the rectifier/regulator. Best to do some testing before replacing parts.

You can test the stator winding with a multimeter set to ohms. Disconnect the rectifier/regulator and measure the resistance between the yellow and yellow/gray wires. Should be very small (less than 1 ohm). If you have infinite resistance then you have an open circuit and the tach and charging circuit won't work. Also there shouldn't be any connection between either of these wires and ground.

Otherwise you might have a problem with your wiring or possibly the wiring conections at your tach,.

 

[oldwood]

Re: 97 225 oceanpro cannot get tach to work

Thank you, I will check that out, I did notice that my volts gage stays right at 12 volts, no matter what speed I am running, and I have had to charge one of the batteries scince I have been running it in the last month.

 

[Seasport]

Re: 97 225 oceanpro cannot get tach to work

OK. It definitely looks like you are not charging. Your voltage should go up to 13.5V at least if you are charging. Check out your stator as I suggest. Wouldn't mind betting that you have break in the alternator windings there. Let us know what you find.

 

[seahorse5]

Re: 97 225 oceanpro cannot get tach to work

Most likely you have a bad regulator/rectifier assembly, about a $225 part. Not only does it regulate the charging for your battery, but it generates a square wave signal for the tachometer.

Make sure the wiring harness for the removed "VRO" is not shortedanywhere near the gray wire. Also look up under the flywheel at the black stator coils and see if any plastic insulation is dripping from them. Replace it if there are puddles of plastic on top of the motor block.

Most of the time these problems are caused by someone using wing nuts on the battery instead of lockwashers and stainless steel hex nuts tightened with a wrench, like the manual says.

the service manual shows how to test the tach and the charging system, but some specialized tools are needed.

 

[Seasport]

Re: 97 225 oceanpro cannot get tach to work

Hey Seahorse.
He's already replaced the rectifier/regulator hence my suspicion about the alternator windings.

 

[oldwood]

Re: 97 225 oceanpro cannot get tach to work

Yes there is some dripping plastic up under the flywheel, checked the stator, no continuety between the yellow/grey and the yellow, looks like a bad stator, when i bought the boat it had wing nuts on the battery, and the connections were loose, I had to wiggle the neg. cable to get it to turn over, also battery cables looked pretty bad, have replaced them and i am going to get the nuts w/ lock washers on the battery terminals, will replace the stator and let you know what happens.