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Old 02 June 2012, 18:51   #1
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Mariner 75 propellers

Hi

Just realised that my new boat with twin 75hp engines has two different props. One is 15 pitch and revs to 5,500 rpm and the other is 19 pitch and revs to only 4,000 rpm. To me 4,000 rpm seems a bit low, although I am certainly no expert! Obviously I need to replace one prop but I'm a little confused as to which size will be best for performance and fuel efficiency. Any help will be much appreciated!
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Old 05 June 2012, 10:54   #2
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Hmm shouldnt they be the same appart from counter clockwise if the gear box is a counter rotating one on one engine

5500 sounds right. I have a 17" pitch on mine and it revs at 5400 flat out.
looks like you may need 2 new props.

does the boat do a large turm with both engines at the same revs?
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Old 05 June 2012, 17:11   #3
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Get them to both rev to 5400, you might find that if you put another 15" prop on the boat will pick up more speed and then the other engine will over rev. Some times with props its all trial and error!
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Old 18 June 2012, 13:02   #4
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Thanks for the replies,

I have put two 17s on my engines, but now they wont even rev to 4500 and i have lost a few knots off my top end speed. So frustrating!!

Im starting to consider a 150hp as this two engine business is slowly becoming a pain!
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Old 05 August 2012, 20:22   #5
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Seems two 15's is the answer.
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Old 05 August 2012, 20:24   #6
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Looks like two 15's is the answer.
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