RPM connection help!

[andyangler]

Hi all,hoping someone can help.I have a yamaha 70HP and a Yamaha 703 control on my boat and i need to connect a RPM gauge up that was on the boat when i bought it.The electrics were already connected but there is a white cable coming of the gauge that was not connected.this is a coaxe type cable and i am hoping this is the only reason the gauge is not working.can anyone tell me where this cable should be connected.Is it to the engine or the control box if so where?
Many thanks
Andy.

 

[realslimshady]

electronic rev counters have 3 connections...usually...positive, earth, and a 'signal' usually from the ignition coil...
what other connections have you got?

 

[andyangler]

There seems to be three electric connections which are all connected up and a signal cable that is running down the boat but not connected to anything,do you think it should be connected to the ignition coil then?
Thanks
Andy

 

[realslimshady]

[ QUOTE ]
There seems to be three electric connections which are all connected up and a signal cable that is running down the boat but not connected to anything

[/ QUOTE ]
4 connections in all?
what about this 'co-ax'?

 

[andyangler]

Yes sorry there is 4 connections in total and the co ax cable is the one that is not connected.hope this helps.

 

[rafiki_]

Just connecting this to the coil may be a recipe for disaster. If you know the make of your guage, try a google to get a wiring diagram.

 

[Wiggo]

Plenty of info on the web about setting up the 703 control, but no mention of a white cable from the tacho. Which model tacho is it?

This might be a good start: http://www.mbcboats.com/perfbull/YamahaMFGaugeKitInstall.pdf

 

[Richard10002]

How about some pictures - may help someone see what you have got?

 

[jfm]

Is the tacho a Yamaha or an after market?

I agree what others have said, normally 3 wires for the tacho function. But the 4th wire is often a lightbulb. That doesn't explain the coax though, as you'd expect 4 ordinary wires not coax. You're sure it's coax? As I say, is it a Yam gauge or a Brand X?

 

[andyangler]

It is not a yamaha gauge,Like richard said i think it would be a good idea to take some pics to show you all.Thankyou all for helping me i really need to get this sorted so i can see if my engine is running correctly.Please bare with me i will take pics 2morrow and post straight away.Thank you all and i look forward to your reply.
Andy