Technical Maximum length of Capillary Tube?

This is for an off-topic but within-era project, but since I haven't found an answer elsewhere I figured I'd put it to the gauge guys here.

I'm returning the control station of a 1950-built boat to a period-correct state, I am having trouble finding electrical gauges (just try finding 12v wings or tulip-needle SW's) but I have, and have found, plenty of mechanical temp and oil pressure gauges. The problem is, we are looking at 20+ feet between the panel and the engine...

What is the maximum effective length of a capillary tube for a mechanical gauge? And furthermore, does anyone know of a shop that can make a temp-bulb line that long?

 

The longest capillaries I recall from Sun or vintage SW is 12' (they typically were offered in 6' or 8' lengths). There's a video online on restoring (filling) damaged capillaries, but accuracy will be an issue.

 

I've got some NOS rear-mount Stewart Warners that have god-awful long senders on them. Probably came from a boat. They are still all wound up with a cosmoline-soaked cloth wrapped around the sender coil. Sorry I'm not going to unwrap them at this time. Just wanted to let you know that they can and were built with really long senders.

 

This probably doesn't help at all, but I found this.

https://www.asap-supplies.com/us/ga...er-temperature-switch-gauge-mechanical-708670

 

If capillary relies upon pressure, the greater length only means time to follow at display is minimally (if at all) affected.
Seems there's a bit of 'Gravitas' involved too.
https://en.m.wikipedia.org/wiki/Capillary_action

 

Check in Hemmings Motor News on people that rebuild mechanical gauges and see how long a tube they can supply.

 

Call Williamsons Instruments.in Chester Arkansas,,,,They will make you anything you want

 

This NOS Stewart Warner rear mount temp gauge has a 30' capillary tube. I think you'll be ok.

 

Thanks guys. I'll call around to a few gauge restorers and see if they can convert one of my tulip-needle temp gauges to a longer capillary.

 

I have a number of a guy if you need any help.