I bought a new old boat last year. It has a Yamaha 225 hp. It is a rebuilt 87 powerhead on an 88 200 hp lower unit. I have had it serviced and worked on several times to make sure it was OK. Yesterday I was out cruising. I have noticed in the past, and yesterday, at low speed it seems to get loaded up so I was blowing it out. I took a nice downwind run at full throttle for a few minutes. It was running about 5700 RPM with no sign of problems. At some point I notice something did not sound right and I backed off the throttle and noticed a rather loud metallic ping and a significant vibration. It kept running. I made it into the dock at least a ten minute run at slow speed. The ping was quiter at idle but it was still there. I could not say where the ping was coming from. The engine did not overheat. I shut her down and let her cool a while and started it up without any problem. Noise was still there. After a prolong cooling period 1 - 1 1/2 hour. It still started.<br />I am afraid it might be a significant problem and will take a look at things this weekend to try to diagnosis the problem. No time yesterday and no tools. I thought a simple solution might be the timing slipping?<br />Help?? 