Yam 115 4str new tachs not working

[cereza]

Hi
I have read a few posts with sim problems but as yet have not seen anyone say they have found a fix.
Am hoping someone has!
I have recently bought a boat that has twin 115hp yam 4stroke 2003/04 models
When i bought the boat both tachs (faria combo's) were not working (factory fitted by boat builder)- i bought 2 new faria gauges and the still dont work.
They are wired to the green wire from ignition, when motors are turning over there is a signal coming thru (tach go up to around 750rpm) when the motor fires and idles the needle drops down to zero and just flickers slightly.
Unlikely that two faulty tach and two broken/faulty signal wires!! - but then i guess stranger things have happened.
I have installed two of trim and volt meter and one fuel gauge - all stem from the same power source (yellow wire from ignition) and all work fine -tachs are wired in with these gauges -have wired tachs seperately and still no difference....

Any ideas welcome

many thanks
Bill

 

[rodbolt]

Re: Yam 115 4str new tachs not working

faria,italian for junk.
should have gone back with yamaha.
are you sure the ground is good? the green wire you want is the dark green from the 10 pin main.
are you sure the tach is set for 12 pole or 6 pulse?

 

[cereza]

Re: Yam 115 4str new tachs not working

Hi there
thanks -only went with Faria as thats what was in and as they ar ea large gauge needed to replace with something that would fit in the same size hole!
Def set on 12 pole (6 pulse)
As for the ground -is the best way to ensure i have a "good ground" to run a lead to the neg on the battery -as i said all other gauges work fine (trim/fuel/voltmeter) but just want to eliminate that as a posibility so is that the best way?
cheers

 

[cereza]

Re: Yam 115 4str new tachs not working

Hi
ok must be getting close to fixing this!
earth is good, poles setting is correct (12), turn ignition on tachs lift or "go to zero"
Got a multi meter on the tach -

at idle -neg of multimeter to ground on tach + to signal wire on tach -reads around 13 volts
when i rev the engine the volts DROP - checked this several times and volts definately drop.... - this is the signal wire fromt he ignition (green wire)

Is this correct?
cheers
Clinton

 

[rodbolt]

Re: Yam 115 4str new tachs not working

nope, you should see a voltage rise on the green wire to ground as engine speed increases.
are you sure the tachs are compatible with a yamaha four stroke?
and the 6y5 digital gauge will fit the standard faria tach hole.
the 6y5 can give visual alarm indicates,trim and RPM as well a total hours and trip hours. trip hours are resetable.

 

[cereza]

Re: Yam 115 4str new tachs not working

HI Rodbolt
thanks - yes i thought the volts should be rising (based on what i have read on this forum) but the reading came from the yamaha green wire from ignition (that goes to the tach) it made no difference if the wire was connected to the tacho or not (volts still dropped)
Is there a point i can run a new wire (sender) from the outboard - under the fuse box cowl on the side of the motor (where the trim button is in the lower cowl) there are three (four?) wires -one is green - is this the tach signal wire that runs up to the ignition? -if so would it be worth running a wire direct to this from the tach and seeing if it makes a difference?
I am a bit lost!

cheers
Clinton

 

[rodbolt]

Re: Yam 115 4str new tachs not working

tach signal has nothing to do with charging system, tach signal on that motor is generated by the ECU.

 

[cereza]

Re: Yam 115 4str new tachs not working

Tach signal comes from ecu -
ok so am i able to run the "green" wire direct from engine/ecu to tach - meaning perhaps the green wire coming out of the ignition is getting interferance or something else is happening causing tach not to work.
This boat has twins yamaha 115's and the same thing is happening on both tachs -so if it is a fault with the ecu? it would seem odd that it is happening to both motors?
Or am i just unlucky :-( !!!!!!
cheers
Clinton

 

[cereza]

Re: Yam 115 4str new tachs not working

Does this mean i have a potential ECU problem (on both motors??)
i checked all fuses (there are only four) all are ok...