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Old 12 September 2023, 13:49   #1
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Country: UK - England
Town: Manchester
Boat name: The Bees Knees
Make: Ribcraft
Length: 4m +
Engine: 60hp mariner
Join Date: Sep 2023
Posts: 4
Ribcraft 4.8 prop choice

Afternoon guys,
New here, recently purchased a Ribcraft 4.8 with a 2002 mariner 60 4 stroke,
Itís currently running a 11, 1/8 diameter 13 inch pitch SS prob, itís really quick into its plane even with a number of people in and easily hits the 6k Rom upper limitÖ Iím after going up in pitch but interested in what others are running? Usual load will be 2/3 adults in averageÖ after a good all round prop for cruisingÖ at the minute 2 adults and a toddler itís sitting at around 20 knots at 4.5k, hitting maybe 28knts WOT, so far been recommended a Mercury spitfire 14 pitch 4 blade prop, although they only come in a 10.1 diameter?
Looking for suggestions and performance reports?
Cheers
Ash
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Old 12 September 2023, 20:50   #2
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Country: UK - England
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Make: XS500/Merc340/Bic245
Length: 5m +
Engine: Mar 60/20/3.5/Hon2.3
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Hi and welcome to the forum.

We have a 2016 Mariner 60 (not command thrust) four stroke on a 5m XS rib. Propped for towing we run a Mercury Black Max 10 1/4Ē x 13Ē pitch which tops out solo at around 31 knots and able to bounce of the limiter at 6000rpm. Also have another Mercury Black Max 10 1/4Ē x 14Ē pitch as a spare which tops out at around 34 knots one up.

Prefer the sharper hole shot and livelier feel of the 13Ē even when not towing at the expense of a couple of knots top speed. However the 14Ē feels more relaxed at 22/25 knot cruising speeds.

Think if three adults aboard was the default load then, at least on our boat, think the 13Ē prop would be my choice.
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Old 12 September 2023, 21:16   #3
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Country: UK - England
Town: Manchester
Boat name: The Bees Knees
Make: Ribcraft
Length: 4m +
Engine: 60hp mariner
Join Date: Sep 2023
Posts: 4
Thanks for the response, notice that my current 13 inch prop is also nearly inch bigger in diameter aswell than what you are running, the majority of my use so far is me my miss and my little lad, the engine jjust seems to be running hard at a mid 20s cruising speed, I might be just expecting too much from
It after coming from a ranieri centre console with a 115 yam 4 stroke on,
Thanks for the reply !
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Old 12 September 2023, 21:18   #4
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Country: UK - Scotland
Town: Tarbert, Argyll
Boat name: The Black Sheep
Make: Ribcraft
Length: 5m +
Engine: Mercury XS Pro 115CT
Join Date: Jul 2009
Posts: 55
Hi Ash, great choice of boat! Try the Mercury prop calculator using weight of the boat. Itís on the Mercury website.

Iíve been on a similar discovery journey recently. Three blade should have less drag, so if you are not struggling to get on the plane, experiencing chine walk or poor handling then Iíd say stick with three blades. Iím currently running a ballistic three blade 21Ē race prop which is really a beautiful piece of engineering. At about 6,000 rpm Iíve had as much as 52.2 Knots. However, itís pretty skittish at that speed and I wouldnít take the kids out with me and run WOT. Iím going to try 4 blades to give improved control but I am dropping a half pitch to try to compensate for the drag and/or get the revs up a little.

I also ran the same boat with Yamaha 90hp two stroke and tried both a 17Ē and a 19Ē K series ally prop. Ran great with both but cavitated a bit more on the 19Ē but then it did have a much better top speed.

The above are quite different scenarios so do check out that prop calculator see what itís saying.
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Old 12 September 2023, 23:58   #5
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Country: Australia
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On a zodiac 470 with a 2014 merc we are using a 12 x 14 vengeance prop which sits in the higher max rpm range with one small person but still achieves 29kts with 5 adults and and spearfishing gear. I believe top speed is around 35kt. I do have a smaller boat with a new Yam F115 which is fun!!!!!
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