Guys, I purchased this motor last year to use for duck hunting in shallow marshes and have gone through 4 shear pins in probably 15 uses. I haven't been that hard on it, simply running through small bits of vegetation seems causes it to shear. Is there something I can check that may be causing this besides hitting something? Also, are there different types of shear pins? I really haven't felt any of the 'hits' and it's really starting to be a problem.<br /><br />Scott