technically your correct on the max rpm for any engine...most of the new engines...ie mpi/fuel injected engines have rev limiters ..thus preventing any damage to the engine at WOT...the earlier engines do not have that feature and can exceed red line settings and thus hit Max RPM's...as stated...WOT is used for knowing the proper prop types and pitch for a given hull design.....if your WOT is faster than the recommended ideal rpm set by merc...then your under propped....if you never reach the WOT range...your over propped...meaning the prop is trying to bite too much water...
even though the merc engines are basically chevie small block engines ....most of the internals and attaching periphials are marine grade and not street grade....plus these engines are beefed up to accept the harsh environments of marine life....ie stronger rods...pistons....valves are slightly different....compression chamber and piston shape is slightly different...cam duration and overlap is way different......water jackets are marinized and pumps are different ....curve on the distr. is different.....basically the engine is designed to run with a full load all the time......kinda like driving your truck up hill in 4th gear with a full bed of junk in the back.....
temps....yes cars and trucks run at a hotter thermostat for mainly purposes of combustion effenciency and pollution laws...but remember the street engine doesn't work as hard as a boat engine does on any given day......a non freshwater cooled engine will run at 160 cuz it's getting water out of the lake or river...sound..ocean....so..it will run alot cooler...gotta remember that a boat doesn't have a giant radiator to help cool it...it gets it's cooling from the outside water....but a FWC'd engine will use antifreeze and a heat exchanger to transfer engine heat to the outside water......having an engine run at 175 gives a big margin of safety from normal running temps to hi temp alarm....this is cuz at the speeds the engine is running..it doesn't take long for the temps to rise quickly.......
just my thoughts here....got a hit of caffiene and couldn't stop typing :mrgreen:
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2008 Bayliner 340 - "Wild Whim"
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