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Old 11 June 2011, 07:53   #1
Country: UK - England
Town: Dorset
Length: 4m +
Join Date: Oct 2003
Posts: 1,410
Ribcraft 4.8/ 60HP Mariner Prop Choice

Afternoon guys, I have recently bought a Ribcraft 4.8 with a 60hp 2 stroke Mariner. The prop is in fairly poor condition and needs to be replaced.
It does however over rev, I can get the rev counter round to 7000 and it sounds like its revving its bollocks off, not idea of speed as its lacking instrumentation but it feels about 30 knots at WOT.
Current Prop is a 14" ally, whats everyone else running I am considering going to a 15".
I want a compromise really of reasonable cruising speed and a decent holeshot, Im not after one or the other just a balance of both.

Any help much appreciated.


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Old 14 June 2011, 11:04   #2
Country: UK - England
Town: bicester
Length: no boat
Engine: outboard only
Join Date: Feb 2009
Posts: 854
Alex if i were you i would phone jason at ribcraft and ask what props were fitted on that combination at the factory when new, you can cause damage by over reving as well as not getting to the factory wide open throttle when running flat out, (note all figers are in gear and on the water NOT reving in nuetral)

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Old 14 June 2011, 13:19   #3
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Country: UK - England
Town: The wilds of Wiltshire
Boat name: WhiteNoise/Dominator
Make: Ballistic 7.8/SR5.4
Length: 7m +
Engine: Opti 225/Yam 85
MMSI: 235090687/235055163
Join Date: Jul 2005
Posts: 12,554
Ads, how bad exactly is the prop that's on there? As in,could it be badly enough damaged to slip to 7k rpm?
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Old 15 June 2011, 14:43   #4
Country: UK - England
Town: Dorset
Length: 4m +
Join Date: Oct 2003
Posts: 1,410
Original prop is fairly shot.

I rang up Ribcraft and they recommended going to a 15. This is a fairly light boat remember, 60HP 2 stroke, single console, on deck tank and no a frame, it is however antifouled.

I bought a brand new 15" prop from the local dealer yesterday and went out, one up with very little fuel and trimmed out it revs to 6000rpm at WOT and a max speed of 33 knots over two runs (GPS).

I also went out 3 up with 30 litres of fuel a wakeboard and loads of other tat,
it maxed out at 28 knots but still pulled 5800RPM.

Cruising at 25 knots was at 5200 rpmish so abit high for my liking still.
Maybe its because I am not used to having a rev counter and ignorance is bliss?
Perhaps it wants a 16"? Peak power on this outboard is between 5 and 6000 depending on where you read.
It didn't exactly feel urgent when 3 up either, kind of like the last 2000rpm were just revs.
After my SR4/ 50HP this boat is abit of a dissappointment, the SR4 you really had to 'drive' and if you got it wrong it would try and kill you, I reckon you could make a cheese sandwich while reading the newspaper on this one at WOT!
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