Hi, I have an old mercury outboard. It is 1968, 65HP model. It has a serial of 2313184. recently, it won't go any higher than 3000rpm in water. I tried to find the root cause of this problem. this is what I did: checked all cylindars(total of 4), all cylindars are working, good sparks. when I remove any of the spark lead at idle, engine has a lose of power. when i put it back on, it restores. The carb was tuned by marine shop not long ago. lower gearcase is only one and half year old. Prop has just been replaced by the shop. Compression are all at 120. I phoned marine shop, they told me it could be a timing problem. <br />Is there a easy way I can verify if this actually is a timing problem? I don't have the timing light to do this. However, if this is really a timing problem, and I donot mind running at 3000 rpm, will this damage my motor further if not corrected?<br />Does anyone know what is the max advance on timing for this engine? I only found a shop manual for year 1972-1984, can't find my year. <br /><br />Thank you for any replay!!