Tachometer Problem

[Gsewell]

Hi all ,
I have a 1996 19ft Maxum 1800 Sr with a 3.0 Mercruiser. First trip out last weekend and once started at idle the tacho gauge was showing 3000rpm .When i started to engage gear it dropped to 1500rpm. After a quick run and up to operating temp and on the plane my revs were showing over 5000rpm.WOT on this engine is 4400-4800rpm.My Speed was around 24mph at crusing speed.I have checked the pole postion on the back on the tacho for the correct 4cyl setting. Has anyone had similiar issue? Faulty tachometer?

 

[Scott Danforth]

check the tach against a good known shop tach

 

[Scott06]

Hi all ,
I have a 1996 19ft Maxum 1800 Sr with a 3.0 Mercruiser. First trip out last weekend and once started at idle the tacho gauge was showing 3000rpm .When i started to engage gear it dropped to 1500rpm. After a quick run and up to operating temp and on the plane my revs were showing over 5000rpm.WOT on this engine is 4400-4800rpm.My Speed was around 24mph at crusing speed.I have checked the pole postion on the back on the tacho for the correct 4cyl setting. Has anyone had similiar issue? Faulty tachometer?

You can try cycling the cylinder switch back and forth between cylinders, sometimes this will clean some corrosion off the contacts and it will work .

may also look for corrosion at wiring points on back and at negative side of coil…

other than that bad tach.

 

[Gsewell]

check the tach against a good known shop tach

Thanks currently trying to arrange with a shop to check this out.

 

[Gsewell]

You can try cycling the cylinder switch back and forth between cylinders, sometimes this will clean some corrosion off the contacts and it will work .

may also look for corrosion at wiring points on back and at negative side of coil…

other than that bad tach.

Ok i will give this a try and check all wires for corrosion before ordering a new tach. Thanks.

 

[juruca]

This was my solution...

 

[juruca]

This was my solution... solder a fixed wire...View attachment 361424