Transmissions temps

I recently had a scare with one of my ZF Marine tranny's. I keep good engine reading records and I noticed about 30 engine hours ago my stbd tranny pressure stated fluctuating +- 20 psi. The fluctuating got worse and the pressure starting rising from 210 to 270 over a period of about 20 hours run time.*

I called ZF Marine and the tech told me to swap the sending units which I did, and the pressures are back to 210 with no flux, so probably some debris was disloged during the swap and perhaps that was causing the problem. The tech also mentioned the normal op pressure is 320-350 and if the units were at 210 like the gauge is reading they wouldn't stay in gear. So I going to replace the gauge.

However in talking to the tech, I mentioned that I cruise single engine frequently and asked his opinion about free wheeling the tranny. The manual says it's OK without limitation, but the tech suggested not doing it for more than 30 minutes because the tranny gets no lubrication when the engine is shutdown. Swapping engines every 30 minutes is sufficient, but he did say that monitorining the temps was the best way to determine when to swap engines.*

So that's what I want to do, but the tranny's don't have a port for temp sending units. I was thinking of just buying a themo couple and attaching it to a bolt near the bottom of the tranny and running a wire to a compatible gauge on the helm.

Anyone have any better suggestions or where I can get a thermo couple and gauge?

Costco a while ago, maybe still, had remote reading oven thermometers. Stick the probe in the meat and you could read the internal temp from the next room. That would give you a wireless solution. I don't know if two in close proximity would interfere or if they have enough frequency options that you could run them side by side.

Ken