J. K. Smith wrote:
snip..
My Nissan 3.5 drives my small Portaboat around nicely but its user
manual and the label on the fuel tank disagree. The manual tells me to
use 25:1 fuelil ratio and the label says 50:1. I've been running 25:1
because it's what I saw first. I don't notice significant smoke and
haven't had it long enough to foul the plug yet.

Any ideas on which way is best or whether this is even a subject worth
discussing? Thanks.

My 1986 Evinrude Yachtwin manual says I can use 100:1 but the dealer
told me a service notice came out a year later advising 50:1. I'd stay
with the 25:1 until you talk to a reliable dealer.