i run a merc60 4 stroke on an aluminum 20 alaskan the slowest i can go without a plate is 3MPH and still maintain charging . put on the large happy troller plate and cut the plate down and can maintain .5 -3.5 mph.
if the merc has the bigfoot gearcase it will only make it worse - you may be able to idle it way down , but will the charging system maintain ?

my02

Rick

Great pointers and help. Sounds like it may or maynot troll slow enought. With out help. I basicly wanted to know if what the dealer was saying was true. Thanks for the help every one.

I have a 50hp Honda on a 1,100 pound boat. I can get in down to 1.5 mph but that’s pushing it. If you want to fish with live bait get a plate!!!

Charlie