Thread: Engine RPM
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Old 12-06-2014, 12:33 AM   #33
BryanF
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City: Astoria
Vessel Name: Florence A
Vessel Model: 47' Sutton
Join Date: Oct 2014
Posts: 173
This is an interesting thread.
Engine manufacturers are interested in the following:
1/ selling engines
2/ having as few of those engines come back under warranty as possible
3/ spending the least amount of resources to make and sell the engine

For a given hull each engine could be adjusted to run a range of propellers with changes to injectors, governor settings, and compression ratios. Adjusting the engine to the requirements of the prop hull combination.
No engine manufacturer wishes to spend the time to do this. No money in it.
So they build an engine and they call it x hp. Every engine they make of x hp in that model is built and set exactly the same. And as a result you change the propeller to match the hull engine combination.
The engine manufacturer knows that most times the guy running the engine is not going to take the time to "drive" the engine watching all the gauges, checking and mapping EGT and boost (if turbo equipped) constantly watching oil temperature and pressure water temperature etc.
They also know that if the prop puts a light enough load on the engine that you can make WOT produce the max RPM the governor is set to you are not pushing the engine to or over the edge of the envelope. That there is no way you can overload or overwork the engine even with the least aware or inexperienced operator. No overload, no overwork, no warranty claims. Happy engine manufacturer and healthy bottom line.
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