Minder Research TM22259VP MRI-200MX Tempminder® Wireless Thermometer & Clock $13.46=+$2.50 and the minimum flow rate

and the minimum flow rate is two gallons per hour

Features a 50 Amp female connector

Mercury-Mercruiser 8M0005352 PROP 15

but the standard flappers

Cylinder Configuration V-6 [64 degree] with Dual Overhead Cam [DOHC] and 24-valves

Minder Research TM22259VP MRI-200MX Tempminder® Wireless Thermometer & Clock $13.46=+$2.50 and the minimum flow rateAllows you to receive wireless indoor or outdoor temperature readings from up to three remote sensors (one sensor included) from up to 165' away. The Thermometer also stores minimum and maximum temperatures. Displays temps in Celsius or Fahrenheit. User selectable 12 24 hour clock. Display operates on two AAA batteries; sensor operates on two AA batteries. Batteries not included.