Funy RPM

[SeaLord]

My Rpm gauge seems ok. Still I have very different RPM for the same circumstances and sound.
I mean, you can tell by the sound and the gas lever position that you are about at 2000 RPM. Erratically what I read on the gauge is much more: from time to time what it should be max 2500 is shown 3500 RPM. Yesterday the gauge got even stacked ay about 2500 and it remained like that with the engine shut down. When I started it again gauge resume correct reading.
I need to mention that my 2001 gl-a 5.7 (sx drive, about 150hrs) has been showing erratic behavior in the last few months. For instance, it did not want to start despite engine was cranking strong, it resumed when I touch cables and sparks but without a clear indication on what it is wrong.
Or it does keep a high or too low idle. revving cable seemed the culprit but then after tuning, it repeats erratically very strange behavior.


So what is the erratic RPM reading probably due to ?

As some of you already know, the boat is in a country where get professional advise is very difficult. So I relay on your advise.

 

[Bondo]

Re: Funy RPM

Ayuh,.... My Guess is, All yer problems relate to dirty corroded wirin' ends,....

The tach, just might be Bad, or dyin',...

 

[muc]

Re: Funy RPM

When you see sparks ---- you have a problem there.

 

[SeaLord]

Re: Funy RPM

thank you
Actually my boat boys proceeded with cleaning all wires leading to engine and in the end the engine started.
Unfortunately he did not systematically clean each cable and try to start so I cannot still tell which one was wrong.

At once the engine started and the rpm came back to sort of normal.
How can I test whether the rpm gauge is working well so the problem is more in the wire ?

 

[alldodge]

Re: Funy RPM

thank you
Actually my boat boys proceeded with cleaning all wires leading to engine and in the end the engine started.
Unfortunately he did not systematically clean each cable and try to start so I cannot still tell which one was wrong.

At once the engine started and the rpm came back to sort of normal.
How can I test whether the rpm gauge is working well so the problem is more in the wire ?

Put a handheld tach on the - side of the coil and compare readings. If both read the same, pull the gray wire off the coil and try again.

 

[SeaLord]

Re: Funy RPM

Thank you
i do not have a hand held tach. If there is no other option I will need to order one to come in the indian ocean. In case do you have in mind a model that may suit my needs ?

 

[alldodge]

Re: Funy RPM

Thank you
i do not have a hand held tach. If there is no other option I will need to order one to come in the indian ocean. In case do you have in mind a model that may suit my needs ?

Did some looking and the only ones I found which stated how high the RPM scale would go was ES models. The first is one (325) which will read up to 12000. The one to the left (328) in the link will go to 20000 RPM.

Electronic Specialties 325 EZ-Tach Digital Clamp-On Tachometer

There are others out there which use a millimeter and a inductive pickup but do not state how high the scale is

LCD Automotive Multimeter with Tachometer Kit Hand Tool Junkie