Old Airguide "Sea Speed Tachometer.

[kbh121956]

I have an old Airguide tach that was used on a 1971 StarCraft 18' SS. The outboard was a Mercury 140 HP tower of power. The Merc was stuck solid. My question is will the tach work on a 4-cylinder Mercury "Thunder bolt ignition system? The only number on the tach is P 6487 and on the back 5 GB as seen in the photos.

 

[Chris1956]

How many wires on the tach? Those oldies used the switchbox (brown terminal with mercury switch) to power them, with 2 wires.

I suspect, that even if you have such a terminal on your 4 cylinder (depends on the year, likely motor needs to be older than 1975), you will only get 2/3 of the proper tach reading.

 

[kbh121956]

How many wires on the tach? Those oldies used the switchbox (brown terminal with mercury switch) to power them, with 2 wires.

I suspect, that even if you have such a terminal on your 4 cylinder (depends on the year, likely motor needs to be older than 1975), you will only get 2/3 of the proper tach reading.

Just a black (ground) and a green.

 

[440roadrunner]

Most those old tachs require a sender. That is a separate box to drive the meter. The meter head is just that--a meter. There is no electronics in the meter head.

 

[airshot]

Cool picture, I have had a few of those over the years...fond memories ....

 

[kbh121956]

Cool picture, I have had a few of those over the years...fond memories ....

I will hold onto the tach. It's like brand new, someone will need it for a restoration project. I know that it's around 1971 because the boat and the old Merc are both 71's. The boat sat in a back yard for about 16 years, outboard up. I bought it and replaced the transom and gave the boat a fresh paint job. Both the engine and the gearbox were locked up, But I had this 120hp that I had just finished up rebuilding. It will make me a good fishing rig for the lakes in my state.