Ok, I'm confused (Don't worry, it's normal).. Why isn't your winch holding? Mechanical winches don't have clutches that I know of.. they have a pawl under spring tension ratcheting into a gear tooth. So what's not holding? If the pawl is popping out of the gear then either the spring is broken, or it's worn, it's a danger, and it's time to replace the winch.
Looking at the pic of your baot I agree with RWilson... move your winch up on the winch post a bit. You want to be pulling on your boat with the top of the winch drum just slightly higher then the eyebolt of your boat... it looks like your's is slightly below.. Also, I never pull my boat up from a ramp without having the safety chain on as well as the winch hook. Neither should you. You can do a search on youtube and see what happened to people and their boats that forgot to.
__________________
1987 V20 w/1987 150HP Yamaha on a Shoreland'r Trailer
1978 16.5 Airslot w/1996 120HP Force on a Four Winns trailer
1996 V21 w/1993 200HP Mercury on a Shoreline Trailer
All towed by a 5.7L Hemi Durango.
If God didn't have a purpose for us we wouldn't be here, so
Live simply, Love generously, Care deeply, Speak kindly.
(Leave the rest to God)
Silence, in the face of evil, is itself evil. Not to speak is to speak, not to act is to act. God will not hold us guiltless.