1975 OMC 225 stearn drive no forward

Need help, I was out on bay, went from wakeless speed to about 25 to 30 MPH was adjusting trim when motor reved up high rpm with no forward. I shut down and went to nuetral and then went forward gear and throttle up, nothing happened just sat and reved motor. I placed in nuetral then reverse gear, reverse works fine. I ended up driving in reverse a mile to get docked. I pulled prop off and pulled cover from drive shaft and that was as far as I could get, do not have big enough retainer ring puller. My gear oil looked good with a little very fine metal in it, found one small shaving size of fingernail clipping but nothing else. If my forward gear is stripped or broken would I be able to hear or feel grinding when I turn my prop shaft? The prop turns smooth and makes no noise when I turn it manually or by power. I cannot find a shop in northern Utah that will work on anything older than 1981,if anyone knows what I need to look for or testing procedure to dtermine whats up I would really appreciate it, summers almost gone.<IMG class=inlineimg title=Confused alt="" src="http://www.marineengine.com/boat-forum/images/smilies/confused.png" border=0 smilieid="10">

did it over heat ?

Thanks for your reply, the motor did not overheat, was running mid range on heat. I will try what you suggested, I forgot to mention that it has electric shift if that matters at all.

check wiring from shifter to forward coil in outdrive.
the F-N-R switch in the shifter has a bad reliability record. The 35 year old wiring anywhere between there and the lower unit may have issues.
disconnect the knife-blade connectors at the transom, while someone shifts (key on) check to make sure 12V+ is present in light green wire in reverse and light blue wire in forward, neither should have any voltage in neutral

With the wiring disconnected from the drive and power shut off, you can check clutch coil resistance - should be about 4-7 ohms between either the blue or green wire and a good ground or batt negative.