Tachometer/Rectifier

[jdupree]

I have a 1992 200 Mercury Offshore. I do have the manual but not where I can get to it right now. I am trying to get the tach to work. If I am not mistaken, does the gray wire that comes out of the engine harness hook up to the tach where it says sending unit? I just need to know what wires coming out of the harness go to the tach.

Does this motor have a rectifier like an omc motor that sends the signal to the tach? If so, where is it located? Thanks,

 

[Texasmark]

Re: Tachometer/Rectifier

Don't have a 200 but on a 90 and 150 it is the grey wire from the Rectifier/Regulator module that drives the tach. The wiring diagram shows tach connections: Purple as 12v, black gnd, and grey as tach drive.

It gets pulses from the rectifier which receives ac voltages from the stator(s) located under the flywheel which are rpm sensitive.

Our 150 has 2 of these modules to get the 40 amp supply and the tach plugs into either. If one is defective, you can move the tach drive to the other.

Mark

 

[Texasmark]

Re: Tachometer/Rectifier

Location on the 150 is center rear of the block, under a plate that contains the trim relays. Wiring to each are yellow (ac inputs), black (gnd), grey (tach drive) and red (12v output).

Mark

 

[jdupree]

Re: Tachometer/Rectifier

Thanks, I will check that out

 

[steplift20]

Re: Tachometer/Rectifier

is your battery charging if so your rectifier is good if not your tach is ng

 

[Texasmark]

Re: Tachometer/Rectifier

I will try this again as I don't know where the other answer went.

That engine may have the 2 ea 20 amp rect/regl modules like the 150. If so, one can give the indication of battery charging if the current is within it's capability (slight battery discharge) with the other being defective/inop/whatever,.

I have never seen the schematic on that module, nor am I familiar with the failure history so I can't advise myself or anyone else as to what fails when they do and what effect that has on the tach output.

Mark

 

[jdupree]

Re: Tachometer/Rectifier

I will try this again as I don't know where the other answer went.

That engine may have the 2 ea 20 amp rect/regl modules like the 150. If so, one can give the indication of battery charging if the current is within it's capability (slight battery discharge) with the other being defective/inop/whatever,.

I have never seen the schematic on that module, nor am I familiar with the failure history so I can't advise myself or anyone else as to what fails when they do and what effect that has on the tach output.

Mark

Thanks, I just bought the boat back in January and the guy said that the tach didn't work even after he put a brand new one in. The tach will drop down to 0 when the ignition is turned on but will not register. Either the tach wasn't wired right or there is some other problem. We have just re-wired the whole boat so I guess I will know something when the motor is started. I just wanted to make sure that we have it hooked up right.

 

[Texasmark]

Re: Tachometer/Rectifier

Going to 0 when you turn the key on is what it is supposed to do. It usually stays at the last rpm your engine was running when you shut off the power (per the service manual)......usually idle.

Mark