tach needle jumping MCX 350

[uliwake]

Hi , I have some issues my tach needle is constantly "jumping" , did try spare tach gauge and same issue . On perfect pass when I put it on rpm mode on idle does not jump rpm , but if I try to wake board with perfect pass in rpm mode it will go up & down slightly making the riding not nice.

Engine runs smooth and constant on idle, no signs of misfire .

So am wondering where is the MDC getting the input for the rpm, is it ignition coil sender ? , alternator? , also which is the pin on MDC for rpm just to check voltage

my engine is 350 MCX 2005

thanks so much

[tommurtha]

MMDC troubleshoot guide.pdf

If it worked attached is an MMCD trouble shoot guide. If not send me your email

[skinh2364]

Are you the original owner? This happens on my boat... I know what it is but I dont have Perfect Pass so it doesnt matter... It happens when I run the blower...some kind of interference from some ones wiring.... anyway, Run a switched power line off the battery to the tach gauge for power(switchted so you can turn it off when the boats off) This would be for testing.. I would go from there, but that is what it is on my boat.

[uliwake]

Thanks tommurtha , is very useful the doc
I am third owner of the boat , it was already this needle issue . I do have perfect pass , but right now is not working well when using speed (paddle) so am going to be trying rpm mode this week end , but the rpm signal surges on gauge would also surge on perfect pass ? Are the both getting the rpm signal from the same source MDC ? so this week end am going to do some trouble shooting to try identify if gauge voltage , if is MDC issue or from rpm sender at the engine...
thanks for the support