Re: Good operating RPM
Every manufacturer specifies a WOT (wide open throttle) RPM range for their engines. Although it varies by engine size, that range is usually specified as 5000 - 5500 RPM, or 4500 - 5500 RPM, or 5500 - 5750 RPM etc. You understanding of engine operation is basically right and basically wrong. The key to engine longevity is to make sure it is supplied with fresh fuel, quality oils, the lower unit is checked frequently for water intrusion, the water pump impeller is replaced regularly and the proper seasonal storage/layout procedures are followed, etc. Then, the next issue is to make sure that with a normal load, when operating at WOT the engine RPM is in that recommended WOT range. In fact it is best for the engine if it is at the top end of that range. Two-strokes simply do not like to be lugged. The key to achieving that RPM is in proper propeller pitch selection. Too little pitch and the engine over-revs. To much pitch and the engine lugs. Obviously the engine has a throttle so it is ok to cruise at lesser settings for best fuel economy. You are correct that prolonged idling can cause a motor to load up so its good to open it up frequently. It's designed to run wide open. I'll bet that engine does not die because of wear-out. I'll bet it dies because of failure to replace an impeller (overheating), lack of carb cleaning (lean carburetion causing a melt down), or lack of proper lubrication (internal pieces finding their way outside the engine). As someone else on this form so aptly puts it: "outboards don't wear out -- people kill them" (or words to that effect).
