Tach not working regal 1800 4.3 merc

[Redquest]

Hey there everyone glad to be back here! Been a while since I owned a boat but back into the game again and very happy to be.

I just purchaspurchased regal 1800 fastrac with a 4.3 merc in it.

One issue im having is the tach is not working it is stuck around 2000rpm and don't move at all there is power to the faria gage as the digital hour meter and lights work on it.

Then today I came across a grey wire in the engine bay labeled tach which just has a cap on the end of it. I've included a pic of this wire.

My question is.... does this wire go to the signal on the tach or is that comming from the tach and suppose to be somewhere on the engine?

Any info would be much appreciated

Cheers and stay safe.

 

[alldodge]

The gray wire does connect to run the Tach and will depend which motor as to where

With the Tach staying at 2000 rpm it may has an issue, it should be at zero

 

[Scott Danforth]

first, take a multi-meter and check continuity from the gauge to that wire.

normally the grey wire goes from the signal terminal on the tach to the negative terminal on the coil

unless its a smartcraft gauge. then it gets connected to the CAN backbone.

 

[Redquest]

Thanks guys ill check out both them options tomorrow

 

[Redquest]

It's a 4.3 mercruiser.
so is that wire mentioned already in the harness that goes to the tach and needs to be connected to the negative side of the coil? Or does.it come off the coil and need to be connected to the tach?

 

[alldodge]

Could sure use a serial number but if its a carb then the wire connects to the negative side of the coil. If its EFI then it will connect to the motor EFI harness

 

[Redquest]

Could sure use a serial number but if its a carb then the wire connects to the negative side of the coil. If its EFI then it will connect to the motor EFI harness

Thank you for the reply , at this time I know it is a 4.3 mpi.
I can get a serial number for you tomorrow.
I am.pretty sure the coil is the square type with the plug going to it.

 

[alldodge]

Being an MPI that lead isn't normally used. It can be used with an external tach for troubleshooting on one that is mounted on the motor. The tach signal comes from the ECM and goes up to the boat tach. My guess is your tach is just bad. Connect a hand held tach to the lead and if it works can connect at the helm to see if signal is still present

 

[Redquest]

0w373396 is the serial.

 

[alldodge]

0w373396 is the serial.

Thanks, yes it is as stated previous

 

[Redquest]

Just an FYI I was speaking to the previous owner as this is a new to me boat.... he informed me the tach has not worked since he has had a replacement motor installed.
of that helps any.

 

[alldodge]

stuck around 2000rpm

Your first post was telling me there was an issue because the tach should always go to zero

The tach signal comes from the ECM, thru the 10 pin connector to the gauge. You can take a ohm meter and connect to the tach wire on the motor to the gauge to see if there is continuity. If there is, then connection is there and its the gauge

 

[Redquest]

Thank you for all your help and knowledge.. cheers!