Do they make a tachometer for my o/b and where can I find one?

[tunerauto]

My 70ish mercury 500 thunderbolt 50hp has no tach or speedo .
Id really like to install one.
Since the motor is a 4 cylinder can I use a sunpro tach that you usually use on a auto.

 

[Chris1956]

Re: Do they make a tachometer for my o/b and where can I find one?

The auto tach probably wont work. OBs use stator pulses to drive the tach signal. I would think most any aftermarker OB or IB/OB marine tach would work. Make sure the brown wire is connected to the rectifier's AC post, as that is the signal to drive the tach.

 

[tunerauto]

Re: Do they make a tachometer for my o/b and where can I find one?

So there is no coil to hook up to? Do O/B have distributors?

 

[Yepblaze]

Re: Do they make a tachometer for my o/b and where can I find one?

Since they made a number of ignition types that would fit your motor's description (magneto, Capacitive discharge with distributor, and perhaps without) I'll try to generally surmise the answer.

The tach you mention might work on a magneto set at 8 cylinders. But it also might not, might not run, or it may just burn out.

For most of the Mercury outboards, the tach is run from between one of the charging wires (usually yellow) from the stator undoer the flywheel, and ground.

Most times the outboard specific tach will have various settings marked as poles, or pulses. And for mine I always used 12 pole or perhaps a #6 (?) setting.