John from Madison CT
Petty Officer 2nd Class
- Joined
- Oct 14, 2001
- Messages
- 176
Hi Guys,<br /><br /> I have a Yamaha 90hp engine. It runs well, has very good compression. (120, 118, 119), BUT I noticed that on the bottom cylinder, the spark plug is always amazingly clean. Like Brand new. No oil, gas, carbon, like new. The other plugs look like they do from a motor, slightly discolored on the electrode, a hint of oil, I think you know what I mean.<br /><br /> I am wondering why the #3 spark plug (lowest of inline 3 cylinder) is like this. I once read that it could possible be a air leak or maybe water getting in somehow.<br /><br /> Tell me what you think guys. FWIW, I don't think the head gasket has ever been changed and this is 12 years old.<br /><br />Thanks,<br /><br />John