Re: what is the prop size and pitch
The prop size and pitch are going to depend on the size and weight of the boat it is on.<br /><br />Before you get into prop swapping, check each cylinder for spark, and perform a compression test.<br /><br />If those check out ok, they it may be time to evaluate your current prop performance and setup.<br /><br />What is the rpm of the engine, at wide open throttle (WOT) with you current prop? Your engine should be reaching 4800-5200 rpm.<br /><br />*************************************<br />Here is some info from the FAQ forum page:<br /><br />Wide Open Throttle RPM's - WOT, Why its important to know.<br /><br />When running your engine at WOT, if it is reaching, but not exceeding the recommended rpm range, the current set up is acceptable. By setup, I mean engine performance, prop, engine height ("x" dimension), trim setting, etc.<br /><br />WOT is used as a measure of how the whole package is working. If your engine is functioning properly, but not reaching recommended rpm, then something is putting too much stress or resistance on the engine. It could be a prop with too high a pitch.<br /><br />If your WOT rpm have been in recommended range, but now they have dropped 500-1000 rpm, you know to look for the cause, before it causes further damage. Perhaps its an ignition failure, a carb problem, low compression, 500 lbs of water in the bilge, etc.<br /><br />Outboards run best when the resistance, or load on the engine is limited to the point, that recommended rpm's can still be achieved at WOT. Any more load than that would "lug" the engine, lowering performance, and decreasing the life of the engine. Not enough load, and you would over rev the engine. <br /><br />The engine operates best when the load matches the engine. Your setup is how you match the load to the engine. On a car, you have a transmission that does this.
