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Old 04-11-2014, 11:49 AM   #13
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City: Long Beach
Country: USA
Vessel Name: Tivua
Vessel Model: 36' Island Gypsy Europa
Join Date: Apr 2014
Posts: 38
Rec to reducte prop size

I have been told by several mechanics over the years that RPM's will not hurt your engine as long as they fall within the safe operable limits recommended by the manufacturer. LOAD is what can reduce the life of an engine (gas or diesel). Overloading and engine so it can turn up is bad for them. For example, MY IG may actually not have much life left in its engine because for the past 3,400 hours, it has been loaded up and unable to cruise at its recommended RMP (and still have the ~500-600 RPM buffer to the max rated load RMP of ~2,500 recommended by Lehman). I'm sure the previous owners cruised her at ~1,800 RMP thinking it was right when they may not have realized that they only had another 100 RMP to go before maxing the engine out.

Well, because I have a spare, I think it will be worth having maybe the four blade turned down a bit and see what it gets me. Speed isn't my ultimate goal although I know as all of us trawler owners do, we count the .1, .2 knots we gain (for current, wind, swell, whatever it may be) and a little more is always nice. I mainly want to make sure I'm not stressing the engine.

This weekend I will take her our and put a mechanical tach on the flywheel and post some accurate readings for everyone to see.

PS, the bottom is very clean and so was each prop. See the attached photo (taken a few days ago).
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