I was given a 1956 3 hp Sea King motor that starts and runs but doesn't appear to be pumping water. I presume there should be water spraying out the three chevron exhaust. I put my had in front of it and get a slightly wet, oily hot hand. It will run in a barrel for about five minutes and then seizes up. Do I need to replace the impeller? How hard is that job for a non-mechanical person and where might I buy one?