Tach hook up

[Bartman]

I have a 1985 Stratos 375V. Can anyone tell me what the original motor was on this boat? It now has a 1974 Johnson 115 and I would like to know if I can hook up the factory tach to the Johnson. The service manual on the Johnson says there is a grey wire for the tach located inside the remote control box. Can I locate the factory tach lead and hook it to this grey wire?

Thanks
Bart

 

[tashasdaddy]

Re: Tach hook up

there are many brands that will work. just have to adjust the pulse for the motor.

 

[Chris1956]

Re: Tach hook up

Bart, If the manufacturer of your tach is still in business, punch up their web site. They may have a downloadable manual on your tach.

Back in the old days, J/E motors had a different connection on the tach itself than the Mercs and other did. If your tach does not have a unique J/E connection, then setting the pulse to match the alternator coil number is what you need to do. If you have the newer style tach, you might visit a marine store and look at the directions on a new tach and pick out the setting for your old Johnny.

Obviously the Johnny is not the orig engine. The original motor probably broke down, and the 115 was available to take its place. Are the controls from the 115?

 

[HighTrim]

Re: Tach hook up

 

[Bartman]

Re: Tach hook up

Chris, I'm not sure if the controls are original from the 115. I THINK I read somewhere that this boat came with a 150 Merc but was hoping someone would could help. I've tried Stratos.com but no luck.

I'm not sure what your talking about when you say "match the alternator coil number is what you need to do". The tach is the original from 1985 so I would not say it's the newer style.

High Trim, I can't see the JPG. It's to small

Thanks for the advice
Bart

 

[Chris1956]

Re: Tach hook up

The 150 Merc would use a 6P setting (I think), the Johnny likely uses a 4P setting. The V4 OMC products has less coils in the charging system, hence the different tach setting.

You need to look up your motor in a tach application guide to get the correct setting.

 

[Silvertip]

Re: Tach hook up

A tach has a calibration dial on the back that allows it to be calibrated for use on various engines. The sense line (the tach signal) from the engine consists of a series of pulses that increases or decreases in frequency as the rpm increases or decreases. To count these pulses, the tach needs to know how many pulses per rev are on that line. In the case of J/E engines that will be either 5 or 6 but for your engine more than likely it's 6 pulses per rev.