Merc 700 (70 HP) Tach and buzzers

[The Hack Shack]

I aquired a 1978 or 1980 Merc 70 hp. It says something on the motor about not using anything but a Merc tachometer. I would like to install a tach as my boat does not currently have one. I also wonder if my motor has a warning sender for overheating. I am going to get a manuel for it but do not have one yet. Does anyone have a suggestion as to what gauges or warning lamps I can and should get to give me visual indication of whats going on back there? Thanks

 

[jimg984]

Re: Merc 700 (70 HP) Tach and buzzers

need to post the year of motor and serial number

 

[The Hack Shack]

Re: Merc 700 (70 HP) Tach and buzzers

4715808 is the serial number I see.

 

[The Hack Shack]

Re: Merc 700 (70 HP) Tach and buzzers

So I think that makes it a 1977.

 

[Moody Blue]

Re: Merc 700 (70 HP) Tach and buzzers

That sticker no longer applies. Can use any marine tach that is compatible with 2 cycle motors. Will need to change the location of the tach signal wire from the switchbox to the rectifier.

Your motor does not come equipped with any warning systems, other than the telltale. You should replace the waterpump impeller if you don't know the last time it was done.

As for gauges, there are many thoughts and opinions out there. I have always prefered a temp gauge, but these motors run cool so the gauge needle always sits on the peg. If it does move, I know I have a problem.

I installed a water pressure gauge on my 71 Merc 800 and the needle doesn't move off the peg. Water pressure is too low to register. Still need to try other take off points to see if it makes a difference.

 

[The Hack Shack]

Re: Merc 700 (70 HP) Tach and buzzers

First off, Thanks for the response.

Secondly, can you please give me a little more detail as to what you mean about moving the tach wire? I also think that my controls have a 3 wire plug on them that is for a tach. Is this true and how do I incorporate it?

Finally, I am nervous about overheating the motor. Do you have any "off the record" suggestions as to what I can install for piece of mind?

Thanks in advance

 

[The Hack Shack]

Re: Merc 700 (70 HP) Tach and buzzers

Also if that plug is for a tachometer, where can I find one? Thanks