Tachometer Markings

[heliman500]

Hi folks,
Looking to replace my tach. The current one still functions but it’s aged look lets the rest of the freshly overhauled panel down.
The original installed engine was an C90, however current installed engine is a C85 with the 200 STC. When I replace the tach I’ll have it customized with correct color markings. I am looking for confirmation of my understanding that the C85 limitations will apply, i.e. red line 2575 rpm. Also, I’m reading conflicting reference to max cruise RPM. Any thoughts? 2350rpm? Thanks in advance.
Wishing everyone all the best for the New Year.
Cheers
Adam

[6643]

There is no marking for maximum cruise RPM. The engine is rated for 2575 continuous RPM. There is a red radial at 2575 and the green arc extends to the red radial.

[edidin]

I just did this on the same engine. Recommend the same route - get the EI tach, have them set the current time to the correct aircraft TT and tell them the redline (2575). Very easy to install - it counts the mag pulses, nothing through the firewall and you cap the tach drive with the included aluminum cap.

[brandon7766]

+1 for the EI Tach. I did the exact thing Edidin did.

[7130]

I was encouraged by this thread to consider the EI tach for my 140, but see that the O200 engine is not on the STC AML. The C150's are though. Am I correct in thinking I can't use the EI tach?

[7130]

I emailed EI and they quickly responded that the STC is by airplane make and model and the engine is only considered for setting up it's ranges and limits.

[brandon7766]

Hi folks,
Looking to replace my tach. The current one still functions but it’s aged look lets the rest of the freshly overhauled panel down.
The original installed engine was an C90, however current installed engine is a C85 with the 200 STC. When I replace the tach I’ll have it customized with correct color markings. I am looking for confirmation of my understanding that the C85 limitations will apply, i.e. red line 2575 rpm. Also, I’m reading conflicting reference to max cruise RPM. Any thoughts? 2350rpm? Thanks in advance.
Wishing everyone all the best for the New Year.
Cheers
Adam

I just noticed that you asked about nominal cruise. I also have the C85 with O-200 STC. I try and cruise around 2350 - 2400 rpm. To my understanding, the C85 with O-200 STC is still legally a C85 so the C85 limits still apply and should still be operated as such. Redline = 2575 rpm and recommended cruise = 2400 rpm.

You will see with the EI tach, it is easy to nail the RPM range you want because of the digital read out!

[edidin]

Seconding normal cruise of 2350-2400 rpm.

[6643]

"Normal" cruise depends on how much you want to spend on fuel.

And, yes, if you have the O200 crank STC it's still a C85 and all the C85 limits apply, including the static RPM limits.

[heliman500]

Thank you all for your informative responses! Much appreciated.
Adam