78 1150 tach

[Erock]

I recently bought an Avenger with a 78 115hp. The motor is not original to the boat and the tach was never hooked up. I pulled the cowling off of the motor to hook the tach up when I saw a sticker that said to only use a Quicksilver tach. I really like the one in the boat(70's style) and if it works I'd love to use it. If it doesn't work, I have a brand new one I could put in it's place. My question is, can I get around using a tach that is not a Quicksilver. I don't want to damage anything (which I assume it will) by using the wrong one. The label does not list a P/N nor did I have any luck trying to find what one I can use. Any help is greatly appreciated. Thanks.

 

[murrayfish]

I have a 1973 1150 that has the same sticker.
I just rewired my boat with a new boat wiring harness that plugs into the motor. In my harness there is an orange wire that goes to the tach. I have yet to hook it up as i'm not that far along in my project. My guess is any tach will work.

 

[GA_Boater]

What brand of tach do you have? The Quicksilver sticker was Merc's way to push sales.

 

[emckelvy]

Some older CDI-equipped Mercs used the special Quicksilver tach and took input off of the brown terminal on the Starboard side of the switchbox. If you see you have a brown wire connected there, that's for the tach and the other end is a terminal in the rubber plug at the front of the Mercontrol remote box.

If the tach in your boat or the other one you have kicking around are meant for alternator-driven sensing, you can use them if you move the brown wire from the switchbox and reconnect it to either of the yellow stator wires at the rectifier. Then you can take connection at the tach plug on the remote box.

Here are links to diagrams which show the 2 different connections. Note the wire colors for the tach plug; white is switched +12V, black is ground, and brown the tach wire.

Old-style with Quicksilver tach wire connected to switchbox: http://www.maxrules.com/oldmercs/Wiring/1966ona/35.jpg

Later-style with alternator-driven tach wire connected to rectifier: http://www.maxrules.com/oldmercs/Wiring/1966ona/50.jpg

Hope that helps..........ed

 

[Chris1956]

In addition to what Ed said...On the 1978 motor, the tach sender wire (brown) should already be connected to the AC side of the rectifier. The 1973 motor probably has the brown wire connected to the brown terminal (non-distributor side) on the switchbox. Obviously that would need to be moves to the rectifier AC post.

Murray, The orange wire is unused on your motor. It is a killer wire on later (1979+newer IL6 motors) motors. Whereas you can use it to power the tach, the brown was the original tach sender wire, and should be connected to the 3 prong connector on the MerControl.

 

[Erock]

Some older CDI-equipped Mercs used the special Quicksilver tach and took input off of the brown terminal on the Starboard side of the switchbox. If you see you have a brown wire connected there, that's for the tach and the other end is a terminal in the rubber plug at the front of the Mercontrol remote box.

If the tach in your boat or the other one you have kicking around are meant for alternator-driven sensing, you can use them if you move the brown wire from the switchbox and reconnect it to either of the yellow stator wires at the rectifier. Then you can take connection at the tach plug on the remote box.

Here are links to diagrams which show the 2 different connections. Note the wire colors for the tach plug; white is switched +12V, black is ground, and brown the tach wire.

Old-style with Quicksilver tach wire connected to switchbox: http://www.maxrules.com/oldmercs/Wiring/1966ona/35.jpg

Later-style with alternator-driven tach wire connected to rectifier: http://www.maxrules.com/oldmercs/Wiring/1966ona/50.jpg

Hope that helps..........ed

Thanks for the links. I'm sure they'll help. There are to wires that aren't connected to anything. I believe one of them is brown I'll have to double check. The only thing is they are not in the engine harness and they are cut off once they exit the motor. Anyway, with the diagrams I'll figure it out. How can I tell if the tachs are alternator driven? If they are not can I wire it using distributor signal? (???? first outboard I've ever owned????)

 

[Chris1956]

Erock, Your motor can use an alternator-driven tach of any standard brand that works for Mercury. Make sure the brown wire is connected to one of the yellow stator wires, at the rectifier.

Murray can do the same, but he may need to move the brown wire from the switchbox to the rectifier.