6hp 4 stroke

[parm]

a bit of advice needed
i have a 2.5m rib + 5hp Mercury 2 stroke outboard (20kg) which is about 12-14 years old with low hours and is an excellent runner. I have the chance of a nearly new 6hp single cylinder 4 stroke (2003 25kg)
with the current setup i can reach 14 -16 knots
Will the upgrade to the 6hp be worthwhile +will i see any change in performance -i was told that the 4 stroke would not give the same acceleration
the cost of the upgrade would be approx £ 200- £250

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[duncan]

performance you should see it happier on the way back from the pub than it was before?/forums/images/icons/smile.gif ie it will do the same but with a little more load.
What you will gain is fuel consumption, starting (although if you have small children the 4 stroke needs a much harder pull than the 2) and ultimately you will have a more valuable rig - you know the value of the existing low hours but no one will pay for that in the future.
If you can stand the extra weight - and surely it's more than 25kg - the Mercury 4hp/4 was about 27kg - then it's a good number.

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[chippie]

It sounds like you are al;ready getting good performance. My concern would be that a single cylinder motor may have more vibration although it will probably run quieter ( if it is water cooled) and have better fuel economy. you will have to manhandle the extra weight every time you use it.
Will they let you try it on your RIB?

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[duncan]

why would it have more vibration than his existing (single cylinder surely) engine?
completely agree about those extra kg - but we don't know if he has the luxury of full davits or otherwise leaves it attached to the rib.

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[jfm]

Parm I have owned both. We have had 3 or 4 of the 4hp and 5hp 2 stroke Mercs (which are the tohatsu motor) and still have a couple. It is excellent compared with other 2 strokes of that size. We also had the 6hp merc 4 stroke till last year. This is quite a bit heavier and you will not notice any significant performance difference, but compared to the 2 stroke it is an incredibly smooth quiet engine. At idle it seems just a faint buzz, and will idel at lower rpm than the 2 stroke without any cough/splutter. Also the cowl on the 4 stroke is quite a bit bigger than on the 2 stroke. They're the only differences really, and if weight is an issue as often it is with these types of tender/boat I would get the 2 stroke

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[chippie]

Sorry about the vibration thing , For some reason I had a mindset about it as I have sometimes used a twin 6Hp. I think JFM has answered the specifics anyway.

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