2001 Mercury 225 EFI, last week i was on plane and the motor started this knocking noise, it became louder and louder, i knew something wasnt right so i shut it down and trolled in. I was told by one mechanic that it wasnt his specialty but it could be a bearing in the powerhead, but he did say that it was a good thing that the motor would still start and wasnt locked up. I don't know where to start, everyone wants money just to look at it, all i want is to know the problem so i dont get ripped for money. The second thing is that the tilt and trim was working fine but one day it gave me problems, then the next trip more problem and now it doesnt work. All the tilt and trim will do is click (under the cowlin) i took the cowlin off with one mechanic and he messed with the wires and what not, then he said it could be that the brushes need replacing, then a friend told me today that it could be a cylinoid problem. At one point the tilt and trim stopped working completely the a few days later it started working, then when i was on the water it stopped again. I have to fix these problems, there going to cost me but I want to get advise from as my people as possible before I start putting my boat in the shop. I know the powerhead will be a mechanics job but can I buy parts for the tilt and trim and install them myself?