Floating Tachometer Question

[jberenyi]

I have a 1988 vintage boat with the breakerless transistorized ignition system. The coil has two sets of wires going to it. One set to the distributor and the other set to the tachometer. I disconnected the speed limiter. The wiring to the tachometer checks out fine and all connections are tight. The back of the tachometer was checked for settings and was even rotated to maybe dislodge some dirt or corrosion and put back to the proper setting for 8 cylinders. The tachometer is a Quicksilver brand. Even after performing all the above the tach still wants to read high by floating from 650 up to about 1200 RPM at idle. As I increase the throttle it will rise to about 3000 RPM and then it will stabilize and read accurately up to 4500 RPM. I checked the tach's calibration with a tach meter and it is dead on. So I ask, could the tach just be on its way out or is it something else?

 

[bruceb58]

Re: Floating Tachometer Question

Mine does the same thing. I have a replacement already to go.

 

[Don S]

Re: Floating Tachometer Question

The first thing I would be doing is checking fuel pump pressures to make sure both fuel pumps are running, during cranking and running. Relays and fuses and possible corrosion could be possibilities on the relays and fuses
SInce it's an MPI, both pumps should run for 2 seconds when the key is turned to the run position. Do they?
What is the SN of the engine. Then I can easly find the proper manuals for you.

 

[JustJason]

Re: Floating Tachometer Question

Wrong thread Don?

 

[jberenyi]

Re: Floating Tachometer Question

The first thing I would be doing is checking fuel pump pressures to make sure both fuel pumps are running, during cranking and running. Relays and fuses and possible corrosion could be possibilities on the relays and fuses
SInce it's an MPI, both pumps should run for 2 seconds when the key is turned to the run position. Do they?
What is the SN of the engine. Then I can easly find the proper manuals for you.

Huh?

 

[cr2k]

Re: Floating Tachometer Question

I would guess the tach is going south. They have capacitors in them that even out the pulses to give a steady reading. When these are going bad the tach will wonder especially at low RPMs.