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Old 10 July 2006, 08:41   #1
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New RIB - advice please!

Hi,

I have just bought my first RIB - a Humber Destoyer 5.0m with a Suzuki 50 hp 4 stroke. She has a twin jockey and a tow / waterski post just behind the jockey seat. It doesn't have any instrumentation bar a Rev counter and a twin gauge.

I would like to fit a log and depth gauge and understand there are some instruments which have the transducers mounted on the stern - can anyone point me in the right direction?

The boat gets up on the plane veryu quickly with 2 people on board - and tops out at about 30 kts - is this to be expected or do I need to think about a prop change to get any faster top speed?

Grateful for any help.

Black
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Old 10 July 2006, 09:40   #2
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30 Knots sounds good to me for a 5m with 2 people with a 50hp 4/, how do you know you are doing 30knots without any instruments? What are you reving to flat out and correctly trimmed? That will tell you wether you need to change prop or not.

You can get many products that are Fish finders, and GPS Chart plotters all in one unit.
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Old 10 July 2006, 10:00   #3
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Quote:
Originally Posted by bluestreak
You can get many products that are Fish finders, and GPS Chart plotters all in one unit.
yep...how much you want to spend is pretty much the limit on that one. I find that my 240x160 screen on my GPS/fishfinder is about the smallest practical for use while moving though. At full throttle I can't read it at all as my eyeballs are shaking too much
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Old 10 July 2006, 10:58   #4
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Advice needed

Thanks for the tips guys - is there a particular brand which has the transom hanging transducer?

I managed to get the following readings from a friends handheld GPS doing two runs to get an average:

3000 revs - 6 kts
4000 revs - 18kts
5000 revs - 21 kts
6000 revs - 24/25 kts
7000 revs - 28 kts (max revs and flat out!)

I am guessing that I don't want to be having it at full revs much? Please let me know on this one.
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Old 10 July 2006, 11:09   #5
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Originally Posted by Black
Thanks for the tips guys - is there a particular brand which has the transom hanging transducer?

I managed to get the following readings from a friends handheld GPS doing two runs to get an average:

3000 revs - 6 kts
4000 revs - 18kts
5000 revs - 21 kts
6000 revs - 24/25 kts
7000 revs - 28 kts (max revs and flat out!)

I am guessing that I don't want to be having it at full revs much? Please let me know on this one.
Its over revving according to the Suzuki Website your max operating rpm is 5900-6500 rpm, http://www.suzuki-marine.co.uk/motors/specs.php which is quite high for an outboard, so if you run it at 7000rpm you will be heading for meltdown!
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Old 10 July 2006, 11:14   #6
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That is FAR too much, i have the same engine and its rev limiter should kick in before it gets that high. The proper range at full throttle is 5900-6500 idealy max of 6400.
What pitch prop are you running?

Any unit that has depth sound/fishfinder etc will have to have a transducer.
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Old 11 July 2006, 03:25   #7
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Hi Bluestreak,

I thought it was a little overkill going that high on a four stroke. Not sure about the prop being new to RIBS and outboards. Will it be written on the prop or is a case of measurement?
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Old 11 July 2006, 06:58   #8
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Quote:
Originally Posted by Bluestreak
That is FAR too much, i have the same engine and its rev limiter should kick in before it gets that high. The proper range at full throttle is 5900-6500 idealy max of 6400.
What pitch prop are you running?

Any unit that has depth sound/fishfinder etc will have to have a transducer.
Makes me wonder if the rev counter is accurate - as you say the limiter should kick in before that.
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Old 11 July 2006, 07:54   #9
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wow that is allot of revs!!!

on the fishfinder, gps hunt, i would recommend a lowrance, its what we use, and I didnt find their options too bad on price, with colour gps's at around maybe 350, although as has been said you can spent however much you like above that amount! fishfinder wise, if its the basics that you want pretty much any will do, and hull mounted transducer is standard, i have a hummingbird, which does the job, no miracles though, garmin do some cheap and cheerful models that work well, approx 80. we use a cobra fixed and a handhelp vhf, both function well, and are well priced, handhelp at 50 and fixed at 115 plus 30 for aerial. these are approx prices though, some may be above or below. have you thought about other equipment? such as flares? spare ropes? emergency anchor? lifejackets of course, what clothing you plan on wearing, as everyday clothes are not suited to boating, especially if you end up in the drink or get wet! also think seriously at taking your level 2 powerboating and vhf courses! as i think although the revs you mention sound very very high, i think speed wise you are about the right area. we once had 2 years ago, a zodiac pro 9 man (4.7m) rib with a 50hp suz 4str, probably slightly shallower 'v' than yours, and we achieved a smidge under 35 knots at max revs, so maybe adjusting the trim will give you different results, obviously weather permitting, and maybe trimmed out a bit on a calm day you will see your top speed. all the best! jonathan
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Old 11 July 2006, 10:32   #10
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sounds under proped, needs more pich,on the front of the prop hub( you got to take it off) or maybe on the back of the hub it should be stamped what size it is.
is this a new set up, or did you get it used?

at 7000rpm you are way outside the limits of the cam shaft, makes less power
at 7 than at 61-6400
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