I need help selecting a Tachometer

[johninmo]

Hello
My Tach has never worked on my boat since I bought it so I started looking at it and I think my tach is bad based on that my battery voltage increases with higher throttle so I was wondering what I need to look for when selecting a tach how many RPMS? Brands to stay away from or to buy ? and what ever else I need to know my boat is a 87 Hydra Sports bass boat with a 87 Mercury 75 HP 4 cylinder

I appreciate any help

Thanks
John

 

[Bob_VT]

Re: I need help selecting a Tachometer

Outboard tach max out at about 7K

Just make sure you buy a tach for a 2 stroke or 4 stroke (depends on your motor) and they are available here tachometer in Boat Parts & Accessories For Your Boat - iboats

The other part of the equation is to make sure your rectifier is okay. If the voltage is varied the rectifier could be the problem and not the tach OR both!

I will move this to the Mercury section

 

[johninmo]

Re: I need help selecting a Tachometer

would 6K be enough ? they all seem top be a little cheaper but if I need the 7K I want to get one that is

Thanks

 

[Bob_VT]

Re: I need help selecting a Tachometer

Yes for a standard motor a 6K marine tach will be fine. Your maximum RPM on your motor should be less than 6000 but be sure it is a tach for an outboard motor. A regular automotive tach is not "pole" selectable

 

[johninmo]

Re: I need help selecting a Tachometer

what pole should I set it on

 

[Texasmark]

Re: I need help selecting a Tachometer

The tach will need 12v and ground plus the input signal which is a gray wire from the engine (in later model engines) and if you have theCommander 2000 remote the gray wire would be attached to the outside of the electrical cable right at the control. The other end would pin 5 of the 8 pin wiring harness connector. I don't remember which year Merc moved the connector inside rather than on the Starboard outside of the engine. I'm talking about the connector inside the engine.

On the rear of the tach is the pole switch. In N at idle the engine should be around 900-1000 which represents a 675 rpm roughly in the water in F which is where idle speed it set. At WOT it should read between 5k and 6k. The poles (I'm thinking 3P is the correct number) are far enough apart that if you have the selector on the wrong pole number the indication will be significantly different than the numbers I mentioned. Just rotate the selector screw till the numbers line up. Shouldn't be a problem

Mark

 

[Bob_VT]

Re: I need help selecting a Tachometer

Which ever tach you purchase will come with a pole setting chart. If you have a 4 stroke it will require an adapter for the tach.