Gas octane?

Maybe a dumb? But I currently have mercruiser 7.4 mpi is it true that this motor is supposed to be ran on 87 octane not 91 I've been using 91 octane will it hurt it if I drop it down to 87 or 89

Will be fine :thumbsup

Won't hurt it one bit

I have a 7.4 carbureted model and prefer to use 91 octane.

Since boats tend to sit around a lot the octane rating slowly declines over time.
So after 4 months will 87 really still be 87? I think not.

Ok thanks for the input I'll just stay on 91 👌🏻