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View Full Version : Newbie tach question---- 68 Mercury 500



NICKINKZOO1
10-03-2007, 08:12 AM
I'm really new to outboard and have a question i need to get figured out fairly quickly. I have a 68 Mercury 500 no generator/manual start. I need to know if i can hook up a tach to this and if so what ones i need to be looking for. I am doing the body work on my 69 GW Invader hull and need to know if i need to fill the hole or what size to make it before i get to paint!!!!

Oh ya i should add,, there is no tach lead in my control box,,, there is the plug on the front but no wires going to it inside. So i need to get signal from the motor!!!
THanks a lot
Nick

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sho305
10-03-2007, 02:27 PM
You may not be able to use a boat tach if it has no alternator as that is what they run off of. Typical they will have the ignition wired under the flywheel and two other wires come out to a rectifier that charges battery and one of those runs tach. There are other tachs like the tiny tach and equis that run off a plug wire. I don't know if you can upgrade that motor with a newer stator...post on the tech forum would be my suggestion, this is mostly for other boat wiring not motors...better yet have a moderator move this thread there.

Groucho
11-03-2007, 10:09 AM
Are you sure on the year? What color is the band/stripe around the cowling? The 68-69 models were an all red stripe and had the first " Thunderbolt" ignitions. They also had a module that allowed you to run the tach on the 4 cyl manual start models and plug it in to the control box. But those parts I'm sure are VERY difficult to now find. I had a manual start 50 hp w/a tach on a 13' Checkmate and remember being able to install all of this when it was new. ( I'm old)

Try www.oldmercs.com and see what you can come up with.

NICKINKZOO1
11-03-2007, 10:06 PM
Yup it's definately a 68,,,,,,,,,, all red stripe with the thunderbolt ignition. The original controller has a plug where there was a tach hooked up at one time. Problem is that the wires in the controller are cut inside the controller and they do not continue back to the motor at all. This is where the problem lies!!!!!

I would like to hook up a modern tach but don't know how to go about it!!!!

150aintenuff
11-04-2007, 11:19 AM
splice onto the cut wires and re run the new wires externally....