The hour-meter is likely just a re-triggerable one-shot that counts up whenever it detects the hash from the spark-plug wire, and resets when you disconnect the power.
Reason for the coarse resolution is that engine maintenance schedules are usually "every XX hours" and not every "XX*60 minutes"
The rightmost, fractional digit is a bit of spurious-precision.

None of this helps you, though: can you generate some high-voltage AC hash to trigger it?

 

The bulb's wire, either one, did not even have to be in the hour meter slot for the induction to be detected and the hour meter counted great.

because the hour meter IS detecting the induction off the bulbs wire.

Granted, given that the coupling is inductive, EMF is not important -- Waveform (spec transition time) and frequency, however, are! --- Out-of-spec functionality of one (or, even, several) units is as expected as it is irrelevant and unreliable...

sorry guys, I do not know much about the circuit or meter! the circuit was made by some wahoo and and meters are from china. The inverters have all the model numbers scratched off the chips, and the meters do not have datasheets. So I am running in the dark too.

problem is the meters we already custom fit for the product we produced, and there isnt room for a different hour meter. We ran multiple tests before we decided to use them, but we didnt run multiple tests with meters from different sellers

Let me get this straight -- You are manufacturing a product from components (CIP The PSUs and HMs) of dubious quality whose specifications (and, it seems, basic principles of operation) you ignore? And, further to this, you suspect the meters are misapplied (15Khz vs 26kHz) -- but now you "can't be bothered" to redesign the enclosure to accommodate a well researched, reliable, design???

If there is no bylaw prohibitive of abetting/supporting shoddy business practice there should be!

If you feel I've 'got you all wrong' I've yet an open mind on the subject...

Tentatively
HP

 

I agree with post #22, plus or minus a few adverbs. The meter you have is completely misapplied here.
If you're dealing with $700 lamps, you could spring for the real thing.
Interestingly, searching for 'boat engine hour meters' eliminates all those spark-plug-wire type things.

 

I agree with post #22, plus or minus a few adverbs.

So...click a, "like" for HP. He deserves to get paid for defining the real problem, and it probably took half an hour to type and parse all those points that I was too lazy to do.

 

... you suspect the meters are misapplied (15Khz vs 26kHz)

Actually that is 15000RPM vs 26kHz, so 250Hz vs 25kHz. No wonder it doesn´t work, more surprising is the fact that OP happend to find a few units that actually DO work.

 

The only suggestion that I might have would be to use a strobe trigger transformer. e.g. http://stores.ebay.com/xenonflashtubes/Trigger-coil-/_i.html?_fsub=2679436010

What exactly you would need to do would require experimentation. A periodic pulse coupled to the wire may be all you need. Going back to the photo-transistor idea. Amplifying your power supply ripple (inductive coupled) with an IA and applying through a trigger transformer might work too.