Tacho reading high - VDO

[Refueler]

On my Penta AQ170 - there is a VDO RPM display on the console and I am sure it is reading high.

At idle - which I would expect to be about 700 - 800rpm ... its reading nearer 1200rpm ..

Question :

What would be usual idle RPM of a such a gasoline engine ... I assumed similar to the 164 Volvo Car its derived from ?

How to adjust the RPM reading ?

I have a hand held Tacho - so I can read the real RPM if calibration can be made ...

 

[scottie]

On my Penta AQ170 - there is a VDO RPM display on the console and I am sure it is reading high.

At idle - which I would expect to be about 700 - 800rpm ... its reading nearer 1200rpm ..

Question :

What would be usual idle RPM of a such a gasoline engine ... I assumed similar to the 164 Volvo Car its derived from ?

How to adjust the RPM reading ?

I have a hand held Tacho - so I can read the real RPM if calibration can be made ...

The tacho needs to be set up initially
Check number of cylinders selected
It doesn’t actually use revs but sparks ️

 

[Refueler]

The tacho needs to be set up initially
Check number of cylinders selected
It doesn’t actually use revs but sparks ️

????

I was reading online about VDO and I see many pages about an adjustment screw in the side that alters the readout .. ??

 

[scottie]

It’s a while since I last saw them but some had a choice of 4 6 8 to select

 

[Refueler]

Will see when later I unscrew panel and look behind !!

I know I shouldn't - never know what you'll find behind !

 

[Refueler]

Camera inside console ... and removed VP panel to see behind ...

The RPM display looks ancient and has quite a few wires to it .. but I cannot see any adjustor or switches etc. I am wondering whether it is a hang-over from when the boat had a 4cyl AQ130 ... she now has the AQ170 6 cyl engine.

If push comes to shove - I could always swap out to a sensor on outside of alternator driven system ... cheap enough and work well.

I will try and photo the back of the panel next time I'm fiddling about there.

 

[scottie]

In my previous replies I did say that this was most likely cause but did not register change of engine

 

[Refueler]

In my previous replies I did say that this was most likely cause but did not register change of engine

Yes I noted .. I wanted to look at rear of display head to check ... sorry - I did not make clear.