Filament that is. If you haven't removed the propellor from your outboard or IO drive as a part of your Winterization procedure, you need to get his on your Spring checklist. If anyone in your crew has ever gotten caught up around your propellor while fishing you may be in serious trouble without realizing it. Monofilament line wrapped tightly around your prop shaft can cause throusands of dollars in damage if left unattended. The photo below shows what I'm talking about.
This fishing line, which may seem pretty harmless on the surface can wreak havock with the lower unit on your engine's drive gears.
The problem is that your propellor shaft is somewhat unique when it comes to gears and transmissions. You see the seals that keep the requisite oil in place around the gears that help drive you in either forward or reverse have to perform double duty with marine applications, sealing in the gear oil, butr because all of this is happening underwater, they also need to seal the water out. This all happens due to horizontally opposed lip seals that are a bit sensitive to interferance from such things as fishing line. You see the line can actually get caught up under the all important lip and cause it to leak; either water in or oil out, depending upon which lip gets impacted. Either way you lose. Oil out means lack of vital lubrication. Water in means dillution of the lube oil. The bottom line is destroyed bearings in gears, with a very high price to repair. Pull you prop at least annually to check for any stray fishing line. The cost to ignore this simple but vital maintenance item is just not worth it.