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Old 01 March 2009, 06:20   #1
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Country: UK - England
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Prop for Mariner (Tohatsu) 30

Hi guys,

On succesfully upgrading my Marathon 25 to 30 by changing carb gasket and timing, i fitted a tiny tach to see what RPM i was getting.

On a 4m inflatable with a 9.99 x 13 prop the max i could get at WOT was 4700 rpm, so below the recommended 5150-5850. I couldn't identify top speed as i didn't have GPS, but will have one next trip out.

From reading other posts on the subject, i need to increase the pitch size?

So bearing in mind i dont want a stainless steel prop(due to where i use the boat), what size would you fit as a starting point and can i expect any speed increase over the current prop and is it worth doing?

Many thanks in advance.
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Old 01 March 2009, 15:50   #2
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Gibbo give me ring in the morning you should have my phone number.
uncle al
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Old 02 March 2009, 13:58   #3
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hello UNCLE AL . YOUR joke was great at the UPDATE .
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Old 02 March 2009, 14:44   #4
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hello UNCLE AL . YOUR joke was great at the UPDATE .
That wouldn't be the Pinnochio one, would it?
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Old 03 March 2009, 02:22   #5
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i just cant stand cheeky kids
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Old 03 March 2009, 03:21   #6
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i just cant stand cheeky kids
Wecome to ribnet uncle al have I gone and missed one of those mother-in-law again, must have done the model update on the wrong day.
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Old 08 March 2009, 08:37   #7
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Fitted new prop and now getting 5870-5900 max RPM. Very happy with the performance but do i need to be concerned this is slightly over the recommended max of 5850?

Advice really appreciated.
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Old 08 March 2009, 13:24   #8
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There is this remarkable new invention called a throttle - if you turn it a fraction it won't over rev.........
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Old 08 March 2009, 13:49   #9
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Originally Posted by codprawn View Post
There is this remarkable new invention called a throttle - if you turn it a fraction it won't over rev.........
Thanks Codprawn,

I just wondered why others were concerned about an engine over revving (didn't think this was good)? So no need to worry then, just use the throttle carefully.

Cheers
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Old 08 March 2009, 18:02   #10
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The reason being the prop should get you to spot on peak revs for maximum efficiency but you are so close and if you are happy with it it's not worth messing around.
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