Rev counter

jhr

jhr

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Royston Vasey
jamesrichardsonconsultants.co.uk
Any thoughts?

The rev counter on my boat is starting to read a little erratically - it over reads by a few hundred rpm and then creeps up until it's showing a patently ridiculous figure (3000 rpm at tickover, anyone?). A blip on the throttle will sometimes make it calm down and sometimes not.

I'm guessing that something is in the process of giving up the ghost. Any thoughts as to what it might be? (It's connected to a MerCruiser 5.0L efi)

TIA
 
A 'SURE FIRE' indication that it is about to blow up, and/or develop massive holes in the bottom all in one fowl swoop! Sell at great cost/depreciation to yourself.....(official dealer version) - or could be a loose cable/earth I suppose (user version!)

Doubt its serious any which way!
 
jhr said:
Any thoughts?

The rev counter on my boat is starting to read a little erratically - it over reads by a few hundred rpm and then creeps up until it's showing a patently ridiculous figure (3000 rpm at tickover, anyone?). A blip on the throttle will sometimes make it calm down and sometimes not.

I'm guessing that something is in the process of giving up the ghost. Any thoughts as to what it might be? (It's connected to a MerCruiser 5.0L efi)

TIA
Click to expand...

Have you run a cable near the revcounter wiring recently, such as the VHF antenna cable? Could be picking up noise in the cable if so.

If not, try following the revcounter cable back to the harness and find all the connectors.

Pull the connectors apart and give em a good clean.
 
Before you go to deep, find out were the signal for the rev counter is comming from, usually the alternator or a magnetic sensor mounted on the crankcase,and check for loose or corroded terminals.With it being eratic it could be an interuption in the signal.
 
jhr said:
Any thoughts?

The rev counter on my boat is starting to read a little erratically - it over reads by a few hundred rpm and then creeps up until it's showing a patently ridiculous figure (3000 rpm at tickover, anyone?). A blip on the throttle will sometimes make it calm down and sometimes not.

I'm guessing that something is in the process of giving up the ghost. Any thoughts as to what it might be? (It's connected to a MerCruiser 5.0L efi)

TIA
Click to expand...


I've got one doing the same. We swapped two rev counters over and it still did the same. (Can you do that)??

I found this lot. aven't tried them. http://www.speedycables.com/
 
It is the grey wire from the minus side of the coil, if you use a test light it should flicker when the engine is running, so start at the coil and then work up to the panel.
Also check you have a supply(purple) and earth(black) to the tacho itself.
 
hlb said:
I've got one doing the same. We swapped two rev counters over and it still did the same. (Can you do that)??
Click to expand...

Only got one engine - I suppose I could try taking the rev counter out of the car (Saab, so basically it's a GM product as well :))

Thanks everyone. I'll start by checking the connectors because I suspect that's where the trouble lies. I haven't done any new wiring or anything (I leave that sort of thing to the "experts".)

As already said by mil1194, I don't think it's anything serious - just irritating...

TK - Do you think I should top up the steering fluid reservoir.....? :D
 
jhr said:
Only got one engine - I suppose I could try taking the rev counter out of the car (Saab, so basically it's a GM product as well :))

Thanks everyone. I'll start by checking the connectors because I suspect that's where the trouble lies. I haven't done any new wiring or anything (I leave that sort of thing to the "experts".)

As already said by mil1194, I don't think it's anything serious - just irritating...

TK - Do you think I should top up the steering fluid reservoir.....? :D
Click to expand...

Well you maybe can, it may not be a yellow cap with a picture of a steering wheel, on your particular boat, and it may or may not cure your revcounter, but it will make you spend a little more money.
Money spent on a boat is good insurance against revcounters and things going wrong, Money spent will not prevent a revcounter going wrong, but it will cure it. Have you a ringfenced faulty revcounter fund?

If not and the connectors with the grey wire running through; when pulled apart, prove to be clean and verdigrease free, and the putting back together of the connectors with the gray wire running through, that are proven to be verdigrease free, do not solve the problem, then a ringfenced faulty revcounter fund may well be beneficial to the problem of repairing a faulty revcounter.

One other thing: Does your faulty revcounter have steamed up face? cos I recall reading somewhere about a little switch on the back of the revcounter getting corroded and requiring switching between 4, 6, and 8 cylinder and back to make a good contact and the faulty revcounter thus been repaired without the need of a ringfenced faulty revcounter fund.
:D

i
 
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