Do you guys recommend changing fuel filters? Spark plugs?

Other than the basic stuff (changing lower unit), which maintenance items do you recommend I do? What should I check/change every year or every so often?

In what motor?

Also, I think you mean the impeller, not the lower unit right? The lower unit change would be pretty major.

What I’ve done so far in my boat once a year is:

Change oil

Change both fuel filters

Change oil filter

Change lower gear unit oil

Change spark plugs

Annually or 100 hours: oil, oil and fuel filters, lower unit lube.

Plugs, thermostat and impeller every other year, but I plan to do those more frequently now that I've drastically increased hours per month.