Don't give up. I have an "07 PT170 with a 25hp 4st and had the dealer mount the same bracket as Dan J. referenced. I use a 5hp 4st kicker. Dealer cut a hole in the rear deck, dug down into the foam to install the bottom bolts. The top bolts were fitted just above the carpeted rear deck and under the corner sheet of aluminum. I use the Helmsmate tiller motor extension handle with the "U" joint, so I steer from the drivers seat. Have had the kicker for 3 years and will trailer short distances 30-60 miles with the motor in place (but I tighten bolts on the adjustable bracket to minimize vibration). Also keep them tight while in the water. It all works OK, but if I were to do it all over again, I would probably look at a 24v or 36v bow mount trolling motor to replace the factory stock version. Probably get just as much speed, problem was I have no good place for the extra batteries. Hope this helps some. Just my 2 cents, but if I were going to drill into the transom, I would have it professionally done.
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