Whats it like when a coupler goes bad? I see lots of grease behind the motor and it seems to rev a little higher like it is slipping, is that indicative of it going out?

sounds like it might be going bad to me. What syle couplers do you have, the HD or standard units?? Are you sure it's grease or rubber?

whichever comes on the 500 efi, I'm pretty sure it is grease or oil, I'm going back down to check today, it was dusk and I noticed it when I docked, with my trailer down, I havent been able to clean the bilge properly but it seemed like it was excessive, I'm going to try to clean it today to see if I can tell where it is coming from.

Everyone I dusted ripped out the splines and was like the boat was in nuetral. There was no "starting to go about it". If the rubber let get like Panther said, you will have bits of rubber all around under the hatch and you would have smelled burning rubber.

As Blue Thunder said.
Theres no starting to go.

If the spline goes it is all at once. The rubber may slip and if you recognize it slipping with in a few seconds and idle it may cool, set up, and allow you to idle home. If you stay in it when it slips it will go away completely. Once it slips once it needs replacement.

thanks for the tips guys, good news is coupler was fine, had a couple valve cover bolts back out and replaced them today, all tight and dry again