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Old 14 May 2012, 12:41   #1
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Correct prop

I have just bought a Destroyer 5.3 with Suzuki DF70 off Fleabay.

Prop is 13 1/2 x15 3 blade.Fuel consumption appears to be crap!!!The previous owners changed the prop from standard.Can anyone suggest a better prop? Not interested in top speed just want to go further than 1 mile per litre at a gentle cruise (17 knots @4000rpm).Or am I being unrealistic?Pretty sure my old DT 75 stroker was as economical as that!!!
Thanks!!
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Old 14 May 2012, 13:44   #2
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I think the standard prop for that engine is a 13 1/4 x 17 3 blade. Are you achieving max revs (5800 rpm) at WOT? What are your revs at that speed - most economical speed is at max torque which is usually around 4000-4500 rpm. 1 litre per NM is a pretty much average for most ribs so you are not that far off.....might expect slightly better.
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Old 14 May 2012, 13:51   #3
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Quote:
Originally Posted by longjohn View Post
I think the standard prop for that engine is a 13 1/4 x 17 3 blade. Are you achieving max revs (5800 rpm) at WOT? What are your revs at that speed - most economical speed is at max torque which is usually around 4000-4500 rpm. 1 litre per NM is a pretty much average for most ribs so you are not that far off.....might expect slightly better.
I do hit 5800 rpm at WOT and a speed of 25knots...ish.
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Old 14 May 2012, 13:58   #4
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I don't think 1lt/nm is too bad, but I would have thought you should be getting more than 25kts out of it. Perhaps little under propped.
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Old 14 May 2012, 14:20   #5
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I don't think 1lt/nm is too bad, but I would have thought you should be getting more than 25kts out of it. Perhaps little under propped.
Yes I agree 25 Kts seems slow - your boat is only a little bigger and probably not any heavier than mine with the same engine and I have seen 38 Kts though 35 is more an attainable max
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