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Old 29 November 2009, 05:30   #11
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Originally Posted by Limey Linda View Post
really "nice" post from the irish guy.
Priceless!!!
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Old 29 November 2009, 06:40   #12
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Originally Posted by martin33100 View Post
I think a Merc 5hp 2 stroke was just under 20kg, I think the Merc 5hp 4 stroke is around 27kg

While I agree you should keep engines as light as possible I would say 7kg is pretty negligable on a 5.6m RIB. If you can get what you want (4 stroke running from main tank) then go for it.

As already said 2.5HP is un-likly to be powerful enough anyway.

That said a 5HP 2 stroke will be marginally more powerful than a 4 stroke, the final part of the equation is of course cost- how do they compare?
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Old 29 November 2009, 14:46   #13
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Quote:
Originally Posted by martin33100 View Post
Hi, I am after a reserve to go on the back of my Avon 560 Rib, I was going to get a 4 or 5hp 2 stroke but a local guy has offered me his very nice yam 2.5hp 4 stroke, I think this would be to small but he said he used it without a problem on his 20ft Hunter, any views on this would be great

cheers Martin
Simple rule;

At least 1hp for every metre of boat to give you something reasonable.

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Old 29 November 2009, 15:27   #14
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I think it depends what you are doing and where.
I have a 2.3 Honda mounted on a 5.8m RIB which gives about 4 knots. It is just a "get to shore" motor.
If I was operating where it was critical and was miles from shore I would have twin engines. Generally I am not usually any more than 5 miles from a shore on my own even if I am operatiing in remote areas and tides are seldom more than a knot or so anywhere unless in very restricted waters which means close to shore.
Its all a compromise and space, cost and weight all come into the equation.
I don't feel there is a correct answer, just what is suitable for the circumstances taking into account all the factors which even includes taking into the account the risk of not having one.
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Old 29 November 2009, 16:43   #15
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Oh I was just messin' and I hope martin33100 knows that, Limey Linda. Or would you prefer I just called you the mexican dude, or the english bloke?

I recall your recent post in response to some minor instance of stupidity:

I'll take a lesson in manners from you when you have some to spare.
Well said that man!!!

Missed that little gem of a comment from Limey Linda.

Musta been out in the hot midday Mexican sun!!

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Old 01 December 2009, 03:46   #16
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That said a 5HP 2 stroke will be marginally more powerful than a 4 stroke, the final part of the equation is of course cost- how do they compare?
Thats interesting Doug, can you explain how a 5 hp 2 stroke outboard is more powerful than a 5 hp 4 stroke outboard?

Martin, do make sure you have the right shaft length which will have a bigger affect on performance than the overall hp. So whilst a short shaft is easy to store, if the prop is behind the transom you are not going anywhere fast. If using a long shaft gets the prop down below the transom in clear water it will be much more effective.

By far the best engine for the job of course is one of those these
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Old 01 December 2009, 05:28   #17
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Originally Posted by Doug Stormforce View Post
If you can get what you want (4 stroke running from main tank) then go for it.
Doug - I would suggest that whilst having the option of running your aux from the main tank might be nice it should NOT be its primary fuel source, because fuel related problems (water, contamination, running out etc.) are one of the more common reasons for needing an aux.
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