Re: WOT
Gil009, your friends 3 cylinder motor is an example of why a "blanket" statement (like your mechanic gave you about "all" engines) is hard to make accurately.<br /><br />If your friends Evinrude is a 56 cid motor it will indeed live longer if run continually at wot rather than at a reduced throttle setting, as produced from the factory. The 56 cid motor -- from the factory -- runs lean in the mid range. Over a period of time the center cylinder will stick a piston. It doesnt happen right away on short trips but rather over a period of time on an extended cruise.<br /><br />It has to do with EPA credits and the fact that the 70 hp model was one of OMC's best sellers. They could get the most credits the quickest by reducing emmissions on that model. <br /><br />Any carb'd motor at mid range runs on full spark advance and relatively little fuel. The water pump may not be putting out the volume it does at wot so combustion heat comes into play. A perfect script for disaster even if everything else is OK (fuel, oil, plug heat range etc). The 56 cid motor was jetted too close to this line and has a reputation for crossing it as jetted by the factory. The closer the top rpm is set to 5000 rather than 6000, the sooner it happens in a "cruise" mode.<br /><br />On most EFI and DFI motors the engine management system has the ability to "see" any lean or hot combustion conditions and deliver more fuel and/or back off the timing. Thats the beauty of the system.<br /><br />Monitoring and maintaining combustion temps is the key.
