On an outboard powered fishing boat, the fuel filter is an imperative item to maintain—yet many of us ignore that filter for years on end. Big mistake. It not only protects your engine from any crud that makes its way into the fuel supply, but is also your second line of defense against phase separation due to ethanol. (Your first line of defense is adding a good fuel treatment, each and every time you fill up).
Let your filter sit for more than one season, and the cartridge can meld itself to the threads on the filter mount via corrosion. Or, worse yet, the bowl could fill with water and eventually contaminate your fuel supply.
If there’s water in the bowl but the filter is still relatively fresh, you can drain it via the petcock at the bottom of the bowl. But never remove a filter, invert it to dump out the water, then replace it. I can’t say I understand the details, but there’s some form of osmotic barrier that gets ruined when you pour water out from the top of the filter. Many people don’t realize this (I didn’t myself until a couple years ago), but the info comes straight from a Yamaha Master Technician. And Yamaha Master Techs are few and far between—there are currently only eight of them in the entire state of Texas, and these are the guys who really know their stuff.
If the cartridge is totally shot and corroded to the threads, more drastic action is necessary. Try putting a wrench on it, but it’s likely you’ll have to fall back on the old oil filter method: use a hammer to pound a screwdriver all the way through the filter, then use the driver for leverage to spin the cartridge off the threads. Quite often the cartridge will simply rip, and you’ll end up picking at it with a pair of pliers until you can remove all of the twisted, corroded metal. Trust me, this is no fun and can take hours.
The ultimate solution, however, is quite simple: each and every year, replace the cartridge. Your outboard will be protected, and you won’t have to spend hours fighting with a chunk of corroded metal.