We ran a fishing resort from 1949 to 1995 so I have ran the same series motors with thermostats and with out,I have saw no difference in carbon build up or plug fouling.
I have a Evinrude Angler 5hp a 1965 model it uses the same style lower unit as the 4hp Yacht twin props are scarce as hens teeth.The 5hp is a very nice running good trolling outboard.I run a lot of weedy rivers and lakes on my trapline and use OMC 3 and 4hp weedless lower unit motors.I have tried for years to figure out a way to use the weedless lower unit on the 5hp Angler but the prop size is too big for the weedless lower unit.It would be great to have the speed of the 5hp with a heavy load.
The invention of the weedless lower unit by Finn T Irgen was one of the high points of better boating you run right threw weeds no stopping to clean off weeds.
