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Old 04 May 2002, 08:22   #1
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Country: UK - England
Town: Iver, Bucks, UK
Boat name: Prime Rib II
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Donkey Engines

Hi Guys... and Gals,

Since my ribbing experience of the last 6 years has been with a twin engined boat and I am about to buy a single engined beast, I need to become an instant expert on auxiliary engines. Can anyone help?

Theory is telling me that a 10 hp or so would be best, (displacement speeds, Archimedes etc.) but I'm keen to get comments from those who have PRACTICAL experience.

My new boat will be 6.3 Meters weighing about 1 tonne or so. Advice gratefully received from anyone with a similar set-up regarding actual experience of.....

1) What auxiliary and prop size, (pitch) you use

2) What real speed is obtained

3) What real fuel consumption do you get

4) Where do you keep it, (i.e. will it stand up to the riggers of transom mounting or do you store it and lug it?)

5) Why on earth do they call it a donkey?

Ta,

Mike Carson
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Old 04 May 2002, 08:46   #2
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Country: UK - Scotland
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Mike I can't answer your question but if you look at the top of the page you will see a 'search' option. Click onto it and then enter 'auxillary engine' as the search words. You will find quite a few threads that may help you.

Keith (mine is only the size of your auxillary) Hart
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Old 04 May 2002, 10:19   #3
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Thanks Keith,

As you say, lots of info but the only speed reference I can find is Alan Winnet's reference to 4-5 knots with a 5 hp engine. Basically I would like to get a minimum of 6-8, (and in a dream world 10) knots out of it because sods law, if it's going to, the main engine will break down half way to Cherbourg. At 6 knots at least I can get back to some land, somewhere in 5 or 6 hours, (carrying 9 gallons of auxiliary petrol). However, if a 10 hp, or even a 15 is still not going to get me that 6-8, then there's no point in going to the extra weight or expense. Might as well get a 5hp and shout help when the scurvy sets in!
According to EP Barrus, the 34 kilo, 15 hp Mariner should, on paper, push my new rib along at "a good 10 knots". But paper doesn't always tally with reality. If someone has practical experience of that size engine, (8,10 or 15 hp) in a 6-7 meter Rib, that would be wonderful.
Then I have to figure out where to put it, and whether I can lift it!
Maybe I should order the scurvy tablets now!

Mike C

**********

Life is like a box of Leggo,
The last bit's always bloody difficult to fit!
(With apologies to GC)
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Old 04 May 2002, 12:30   #4
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My life is like a box of Leggo - there are never quite enough pieces for what I am trying to build!

Keith Hart
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Old 09 May 2002, 04:56   #5
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Mike C,

I use a Yamaha Malta (3.5 hp) on a heavy 5.3 m Bat (around 1 ton). Measured by my GPS on a FLAT sea it gives me 3.5 knots with 3 persons on board. It is NOT the ideal horse power for my boat but it's all I've got.
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Old 09 May 2002, 05:52   #6
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Here's what the DONKEY who owns 'Quicksilver' uses as auxillary power!

Keith Hart
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Old 09 May 2002, 06:19   #7
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An interesting debate;I had a 10HP on a 27ft. sportscruiser someyears ago which I think weighed approx. 2.5 tons.I had to use it once and it got me in (with the tide) at about 3kts. in a flat calm

I don't use one on my RIB because


they tend not to be used and may suffer as a result

they may affect the trim/ performance of the boat

in any weather offshore your probably better with a sea anchor and get help -the auxilliary is unlikely to get you anywhere

engines are more reliable these days (hopefully)


Overall not an easy call
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Old 11 May 2002, 07:04   #8
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Many thanks for the comments. I will go on musing. I still don't like the idea of being miles from anywhere with absolutely no back-up. I did have one e-mail that said 6 ish knots WAS obtainable with a 10hp in a six meter boat.... but they aint light!

Perhaps I could launch a kite and get that to tow me?

Any more experiences appreciated

Mike C
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Old 11 May 2002, 08:02   #9
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Just look at the SoC updates re auxillary engines! What would they have done without one?

I'm sure there was a thread about which was best, twin engine or single engine. I guess that you have made your mind up for a single engine set up but you're going to miss the peace of mind of having a 'spare' if needed.

Up at my house in Scotland, in the summer there are always boats out in the Moray Firth, so if you need help you can get a tow. However in the winter I'm usualy out on my own so if I had engine problems it's a case of oarpower. I am aware of this and in the winter I stay closer in and only take the boat out in places where there is somewhere to row back in to!

I should imagine that you would not be able to get far with a pair of oars with a boat your size.

Keith (talks a load of rowlocks) Hart
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Old 12 May 2002, 17:19   #10
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Mike,

I am with Phil on this one. This year I have invested in a sea anchor, a marine radio and hydraulic steering and last year I changed from a Mercury 90hp two stroke to a Yamaha F115.

My son insists that we should have an auxiliary, but I think it's hassle and clutter and just pray that he never has the opportunity to say "Told you so !"


All the Best


Whiteshoes

p.s. Please see my posting on Prime Rib on the 5-6m thread
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