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Old 04 September 2007, 13:15   #1
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Country: UK - England
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Ribcraft 4.8, propeller pitch?

Recently changed rib to a Ribcraft 4.8, the prop pitch on it now is a 13p and I get around 36 mph at over 5800+ rpm (over revving I know) with 2 1/2 people on board and about 40 l of fuel.

The engine is a 2 stroke mariner. Just like to know if anyone else with a similar set up can point me to a starting point for a pitch, I would guess around 15-17 but as ordering from the states would like to get an idea before I do.

I require decent cruise speed, not to bothered about hole shot but may take up to 5 people on very rare occasions.
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Old 04 September 2007, 13:56   #2
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Country: UK - England
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have a look at this

http://www.turningpointpropellers.co...propellers.php

there is a prop size calculator

I used it to calculate the size for mine - came out at a slightly higher pitch than I needed -saving me fuel!! - I just picked a similar rib on the selection as they don't have ribcraft but there's a good selection

Also - I ended up buying a hustler prop - seems OK so far

Cheers
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Old 04 September 2007, 15:27   #3
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Whats you engine Max RPM supposed to be?

When you say you are getting 36 knots at 5800 RPM is that Wide open throttle?

Basically you are looking at about a 200RPM drop in Revs with each increase in Pitch so you could find a 15 is fine however if you want to get best crusing performance maybe go with the larger 17" and then keep your current prop for when you have more people on the boat or need better hole shot for waked boarding etc.

The thing is until you put the prop on and try it you won't really know if its right thats the pain of prop testing and its why I have now got through about 5 different props on my boat before I found the right combo and trust me you won't get much for them 2nd hand either.

Chris
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Old 04 September 2007, 15:31   #4
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Country: UK - Wales
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Why are you ordering from the states? I would expect the carriage from US to equal the cost of a decent s/h ally prop in the UK.
There are loads of these props around - buy or borrow one s/hand and give it a try. If it doesn't suit, try something different.
13" pitch seems too fine for the set-up, but 36mph is good for a 60. Are you sure it's a 13" pitch?
If you bought it from Pacer Marine, try asking them if they have a coarser pitch prop for you to try. Good luck.
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Old 05 September 2007, 04:29   #5
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Thanks to all

purdster
What pitch did you use in the end?

Chris
Wish it was 36 knots, would be happy then. Quoted top revs are 5000-5500rpm, the rev guage seems to stop on 5800 though so pretty sure its doing closer to 6000 with this prop, but havent kept it there for any more than a few seconds for fear of a big bang and then loads of tears, mine.

Downhilldai
The part number on the prop finishes with 13p, This stands for a pitch of 13? the 36mph was a gps reading but its more the high revs that concern me.

The importing from the USA is what I have done before, the pitch on that one though was a little coarse, hence the post. The prop I was considering is a SS one and I have seen a 17 pitch SS for $199. The last one I ordered was around 30 postage and 20 import duty so 150 for a SS prop is unbeatable in the UK?

As for pacer I live in Brum and rib in poole/devon so a bit of a journey, next trip is Anglesey, would love the prop for then
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Old 05 September 2007, 09:00   #6
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17 pitch which is a bit over the ideal but seems to have helped the economy - but not the top speed - its lower than having a smaller pitch on there - but I'm using 2/3 the fuel............!!
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Old 05 September 2007, 13:51   #7
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I can see where you're coming from in terms of value, but it won't be much use if you end up with the wrong prop - ask IBWET
As this motor is relatively popular, there are plenty of s/h props around for you to try for size (pitch). When you get it right, consider a SS one then. Personally, I'd stick with ally on a 60hp outboard, as the performance gains of a stainless will be marginal at that hp and there's a risk of damaging small gears in the leg if you happen to hit something with it.
Also be careful comparing props used on different make outboards, as the gear ratio may be different to yours.
Good luck - FWIW I'd try a 15" pitch first.
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Old 06 September 2007, 08:08   #8
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Thanks to all, points taken, think I will go for a second hand alli 15 or 16" inch pitch, just got to find one now. Will post results when I have them.
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