Rev counter Problems

[stul]

Hi
Only used the boat Humber 5.5 rib once so far been mostly on the drive, since buying a month ago,fitting it out with Gps and Vhf, but noticed the Rev Counter does not return to 0 its on nearly 1000 rpm mark.
If it does not read correctly with engine stopped can I expect a correct reading when running?
It is a Mercury Gauge working off a Mariner 75 hp 2 stroke
Thanks Stuart

[Poly]

stuart - i think some tachos are specifically intended not to sit at zero when the power/signal is off. its supposed to protect the mechanics?

[stul]

Originally Posted by Polwart

stuart - i think some tachos are specifically intended not to sit at zero when the power/signal is off. its supposed to protect the mechanics?

A friend of mine Top banana said something like that as well, he is usually knows what he’s on about, but thought I ask

Thanks Stuart

[J S]

Originally Posted by stul

A friend of mine Top banana said something like that as well, he is usually knows what he’s on about, but thought I ask

Thanks Stuart

Usually if you just turn the ignition on they will go back to zero, I think reason for staying at around 1000 is thats what the engine rpm is when you switch it off.

James

[alystra]

Originally Posted by J S

Usually if you just turn the ignition on they will go back to zero, I think reason for staying at around 1000 is thats what the engine rpm is when you switch it off.

James

Yes, it's a 'feature'.

[Nasher]

When I finally upgraded to a boat worthy of a Revcounter a few years ago I embarassed myself by taking a Revcounter back to the shop I'd just brought it from. I knew it was a used one, but had been told it had been fully tested.

I'd got back to the car, opened the box and found the needle at about 1500rpm. I went back in all stroppy and demanded another one that wasn't broken.
The assistant explained the situation and even flashed it up to a battery in the workshop to prove his point.

As I understand it the needle will stop at the point at which it loses a signal. which at the right point in the cycle can even cause it to drop below 0.

Nasher

[JSP]

Mine stays at 1000 when there's no power to it too.

[J S]

Originally Posted by JSP

Mine stays at 1000 when there's no power to it too.

It will just stay at whatever revs the engine is doing when you switch it off.

James

[JSP]

Nope, tried it a few times when I was out yesterday after reading this thread. No matter what it always goes to 1000 even if the revs where below that.

[stul]

Well thanks for the interest shown, I see one or two have similar reading, my main concern is, if the reading at the top end 5000 + revs is correct and I can rely on this, my 75hp Mariner engine plate states 5,250 rpm
Stuart

[alystra]

Originally Posted by stul

Well thanks for the interest shown, I see one or two have similar reading, my main concern is, if the reading at the top end 5000 + revs is correct and I can rely on this, my 75hp Mariner engine plate states 5,250 rpm
Stuart

Having switched off my engine, 1000 is indicated. If I turn the ignition back on then off, 100 is indicated. I take that to mean that my instrument over reads by 100 revs. That might be rubbish, but I don't think it's a problem.

[Ian Sharlot]

Originally Posted by stul

Well thanks for the interest shown, I see one or two have similar reading, my main concern is, if the reading at the top end 5000 + revs is correct and I can rely on this, my 75hp Mariner engine plate states 5,250 rpm
Stuart

I would say your rev counter is ok. It sounds like you should go up a pitch or possibly two on the prop, what prop have you got on at the moment?

[stul]

Ian
I think you probally know this boat, just bought it from Jono,s friend "H"Andy seems to go well,38.6 Knots down the Menie (short burst) trimmed out, you know what its like first time out steady ,steady give it some lol.
Any way never made a note of revs when flat out.
Prop is Stainless Mercury 48-1 16988 18P
Thanks for your interest
Stuart

[Ian Sharlot]

Hi Stul

Yes, I do know that one. You will have great fun with that one, it is a nice rib,