Last Weekend on the lake had the boat loaded down and leaving the doc trying to get on plane felt the motor lurch and made a bang noise kinda , we stopped an checked everything thinking I had hit a underwater stump but all was fine so we kept going well it would do every so often under load an kept getting worse an worse untell we just pulled it out of the water. Motor ran fine just sounded like maybe it was slipping a gear or linkage was jumped out of gear or back in? But couldn't tell ,how can I check the lower unit to see if it's that ? There were tiny shavings in the oil wen I stuck something in the filler hole, and no water.