Re: 1975 merc. 500 50 hp.
Hey, Lazenby. It almost certainly is grinding . . .Lower ends don't shift like an auto stick shift. The gears are "square" cut rather than angled and the "clutch" is a "dog" (in or out, no inbetween). Autos can be eased into gear because synchronizers equal the speed of the angle cut gears before they actually mesh and the angle pulls the gears into full meshing. The grinding you are getting is the ends of the gear teeth banging against one another, and it is bad news.<br /><br />Pull the lower end drain plug and check the amount of metal particles stuck to the magnet. A few is normal. If it is heavily covered, drain and flush it then refill with Merc or OMC grease.<br /><br />Check your shift linkage. The cable may have stretched so that it is not going all of the way into Rev. If so, adjust the linkage.<br /><br />The most likely cause of the grinding is easing it into gear. A quick, positive shift may produce a mild clunk, but that is normal and does no harm. "Dog" clutches should be shifted quickly and positively.<br /><br />If not too much damage has been done to the gears, you should be okay. If it starts jumping out of gear the teeth are too far gone and I'm afraid you are in for a fair sized bill to overhaul it.<br /><br />Good luck.<br />JB
