this is the second distributor that l went through. it is for my mercruiser 140 4 cyl. 1 st problem was the distributor drive gear got chew up so bad it wont turn the rotor. 2nd same thing but notice it before it got really mess up. so was wondering what could have cause it? bad cam bearing? or the camshaft itself gears on the cam doesnt look to mess up but its still in the engin

Hmmm? sounds like u r getting a lot of endplay in the cam the cam has a plate behind the timing gear held in with two screws (thrust plate) if it backed the screws off could let the cam ''walk'' back an forth wearing the dist gear teeth one easy to check is to try & push the cam gear forward & back with the dist out of its hole in the block take a screwdriver & ''CAREFULLY'' push the cam gear torwards the rear & then towards the front sould only feel a few thousands of an inch clearance but if it moves quite a bit u need to pull front timing cover & investigate why hope l helped u also check oil pump drive for binding good luck

If ur engine is late 1990 is MC140 this is a very unusual problem. The engine is unique to Mercruiser. If the distributor failed, l will bet that this engine has been ''rebuilt'' or other service done because of problems with the exhaust manifold. Bottom line is that u need to have it checked by an ''engine'' man. It sounds like the camshaft is not properly aligned. My memory is that there is a long shaft that drives the oil pump, that is a part of this distributor. Secondly this dist. is ''non-automotive'' & I've only replaced one in 20 years, & that was because of a bearing failure.