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Old 18-03-2017, 01:51 PM   #1
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Country: Brixham Devon
Occupation: Hotelier
Interests: Music Cars Boats
Boat make: Delta 25
Engines: 5.7 v8
Cruising area: South coast

Join Date: Jan 2012
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propeller pitch

Hi, looking for some advice on propeller pitch or what pitch people have used with similar engine / craft. I have a 1975 Delta 25 Deep V power cruiser, and run a new 5.7 v8 vortec 300hp assumed, running an SEI alpha Gen 1 1.50-1. The boat currently has a standard alloy 19" prop and whips up on the plane with no dramas pretty darn quick but tops out at only 35 knots and only revs to 4100rpm and I understand that 4800 is optimum for this engine, I have just taken the old flame arrestor off which I am led to believe is too small and put the correct one for the carb on (much bigger) and I had some inline exhaust mufflers which looked very restrictive which I have now removed, so I might gain some revs there. Before I re launch I want to put a stainless prop on it so should I go down to say a 17" ? is 19" over propped for this setup? if I do put a stainless one on I was thinking Michigan wheel ballistic. many thanks in advance.
Edward,
Brixham Devon.
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Old 20-03-2017, 03:49 PM   #2
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Country: isle of wight
Location: on a rock
Interests: boats,boats and boats
Boat make: Cougar 21
Engines: Merc 2.5 promax 150
Cruising area: solent

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Quote:
Originally Posted by EdBence View Post
Hi, looking for some advice on propeller pitch or what pitch people have used with similar engine / craft. I have a 1975 Delta 25 Deep V power cruiser, and run a new 5.7 v8 vortec 300hp assumed, running an SEI alpha Gen 1 1.50-1. The boat currently has a standard alloy 19" prop and whips up on the plane with no dramas pretty darn quick but tops out at only 35 knots and only revs to 4100rpm and I understand that 4800 is optimum for this engine, I have just taken the old flame arrestor off which I am led to believe is too small and put the correct one for the carb on (much bigger) and I had some inline exhaust mufflers which looked very restrictive which I have now removed, so I might gain some revs there. Before I re launch I want to put a stainless prop on it so should I go down to say a 17" ? is 19" over propped for this setup? if I do put a stainless one on I was thinking Michigan wheel ballistic. many thanks in advance.
Edward,
Brixham Devon.
Mirage 19 worked down a bit would work
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