Reserve outboard size again

[martin33100]

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

[Hightower]

Originally Posted by martin33100

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

Too small Too small!

I tried a 2.5hp on the back of a 5.4m RIB in the sheltered waters of Portsmouth Harbour. Wind speed was about 15 knotts and just had no steerage what so ever.

Go for a 5 or 6.

[willk]

Your title-line suggests that you know that this is a recurring thread. Which is why you had planned on a 5hp. Which is why you know the "Local guy" is a lying no-good cnut. But you'd like us to confirm it anyway

Fair 'nuff. He's a fcukin' lyin' cnut.

[martin33100]

Originally Posted by Hightower

Too small Too small!

I tried a 2.5hp on the back of a 5.4m RIB in the sheltered waters of Portsmouth Harbour. Wind speed was about 15 knotts and just had no steerage what so ever.

Go for a 5 or 6.

Ok 5hp it is then, would you go for a nice used 5hp 2stroke with a built in tank? or get a later 5hp 4 stroke and run it from the inbuilt Rib tank?, I was thinking 2 stroke though for the weight

[Hightower]

For that size RIB, keeping things as light as possible is pretty important and a 2 stroke fits the bill. However I like convenience and would like the option to run off the main tank. I would see if you can get a 4 stroke with an internal tank, but plugging it into the main tank has advantages.

[martin33100]

Originally Posted by Hightower

For that size RIB, keeping things as light as possible is pretty important and a 2 stroke fits the bill. However I like convenience and would like the option to run off the main tank. I would see if you can get a 4 stroke with an internal tank, but plugging it into the main tank has advantages.

I think a Merc 5hp 2 stroke was just under 20kg, I think the Merc 5hp 4 stroke is around 27kg

[Cypman]

Aim for a minimum of 1HP for each metre of boat length and then find the lightest O/B you can.
Tohatsu 2 strokes are reliable and light

[Limey Linda]

Originally Posted by willk

Your title-line suggests that you know that this is a recurring thread. Which is why you had planned on a 5hp. Which is why you know the "Local guy" is a lying no-good cnut. But you'd like us to confirm it anyway

Fair 'nuff. He's a fcukin' lyin' cnut.

really "nice" post from the irish guy.

[willk]

Originally Posted by Limey Linda

really "nice" post from the irish guy.

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:

Originally Posted by Limey Linda

You must be Irish

I'll take a lesson in manners from you when you have some to spare.

[Downhilldai]

[Mollers]

Originally Posted by Limey Linda

really "nice" post from the irish guy.

Priceless!!!

[Doug Stormforce]

Originally Posted by martin33100

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?

[CJL]

Originally Posted by martin33100

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.

CJL

[BruceB]

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.

[tonymac]

Originally Posted by willk

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!!

[Pete7]

Originally Posted by Doug Stormforce

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

[Poly]

Originally Posted by Doug Stormforce

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.