Rpm Of Trolling Motors Another TACH Question: 115 Merc 4 Stroke?

Another TACH question: 115 merc 4 stroke? - rpm of trolling motors

Tach rev / min is not available and cut to reduce energy consumption. Voltage indicates that 14 + run if min around 4000 rpm. Regulator / alternator was mentioned in a similar situation already? Or is it a cable? Engine has approximately 40 hours, 20 minutes of the last of them in the lagging @ 1000 rpm or less. Opinions are welcome