Grumman 17 CC steers HARD to port-thoughts?

[bulletbob]

17 foot Grumman CC w Merc 70,, Posted about this late last season on another forum, and most thoughts were trim zinc adjustment, or motor depth on transom.. Fair enough, but I still have the problem, after checking both issues... Here is the current situation- The boat steers hard toward the left/port.. Does NOT pull!.. Always tracks straight.. However, it simply turns extremely hard when trying to steer left under power. even at idle speeds. It turns soft and perfect as long as the prop is NOT engaged. it has a brand new teleflex cable.. I think the previous owner may have tried to fix the problem with a new cable to no avail.. Tried adjusting the zinc trim tab both ways to make sure I was not thinking backwards.. Either way makes NO difference, no matter how much or how little I turn it.. Then I noticed the motor was right on the transom and I figured it might be adjusted too low... Mercs have 5 holes .. I went from the top hole to the third one, not wanting to go too high.. Again NO difference at all.. Boat simply does not want to turn left even at idle speeds.. Once the boat is in neutral, prop not turning its fine.... Here is another issue that might be related.. The boat porpoises horribly at planing speeds, even in perfectly calm water unless its trimmed all the way against the transom. If you lift that motor even a little, the performance drops, and she porpoises uncontrollably... I am starting to think perhaps this might have a problem with prop pitch more than anything else, but am not sure, and need opinions.. She planes nice with the motor trimmed all the way down, but again steers hard as a bear to port at any speed until its taken out of gear.. I have owned small boats for over 40 years, and have never seen this before, and right now I am at wits end.. I would appreciate any good information.. As of now, all I can think of is raising the motor up the last 2 holes higher on the motor bolts, or trying a different prop... I covet your experience and wisdom with this issue.... bob

[PAFireGuy]

Bob, how about the possibility of a damaged or bent vertical pivot shaft?
Maybe with the boat out of the water, attach a ratchet strap or come-along between the skag and the trailer or transom to represent the load of the motor when in gear, and try to steer the motor. Obviously be careful not to apply to much pressure or you'll have bigger problems.