Adding a new tachometer to an older Johnson

[dOb]

I have a 1979 Johnson 85 hp Seahorse. I?m in the process of rebuilding the boat that it lives on. I?ll be adding a Tachometer to the instrument panel.

Question: when I wire in the new tachometer (an after market marine tach) can I just set the pulse switch and wire it in and I?m good to go? The reason I ask is that my last motor was a 1974 Mercury and in order to get a new tachometer to work, I had to cut into the wiring harness at the motor end and reroute some wires (to the rectifier I believe). Will this be the same situation or will the new tach work on this old motor?
Thanks.

 

[F_R]

Re: Adding a new tachometer to an older Johnson

1979 isn't old technology when it comes to tachs. Use a standard alternator-driven tach, set it to 6 pulses, hook it up and you are ready to go.

 

[dOb]

Re: Adding a new tachometer to an older Johnson

Great! Thanks. I don't know much about this motor. I just wanted to be prepared. Since I'm rebuilding the console, I'm thinking of only installing gauges for tach, volt and fuel.

 

[Bosunsmate]

Re: Adding a new tachometer to an older Johnson

If i was wanting a very thorough set up id add a temp guage for each head as i dont like the way the cooling system works at idle on these with only a tiny bypass hole which if it gets blocked leads to the whole water flow stopping. I just find temp gauges have much better info than a overheat horn which may or may not work

 

[boobie]

Re: Adding a new tachometer to an older Johnson

Instead of a temp gauge I'd install a water pressure gauge. Some of the temp gauges have been known not to be to accurate.

 

[dOb]

Re: Adding a new tachometer to an older Johnson

That maybe something to consider. I had a poor circulation/overheating problem on the last motor I had. It ended up being a cracked exhaust baffle. After I fixed the problem I got in the habit of watching for circulation and checking the temperature of the discharge water by hand. That motor didn't even have a warning horn, so I figured I was already ahead of the game with this one.