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Old 12 September 2014, 16:01   #1
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Ideal engine size for my 5.8

After my 135 v6 let go on my boat I'm looking for a replacement engine.

My current search is centred between 90 - 115 as the 135 was way too much for my boat and also for what I wanted.

So I'm after a more frugal engine that I can use for normal cruising/travelling that does not rape me on fuel costs.

I would obviously be more than happy with a 90hp but would I be shooting my self in the foot with this size engine with it possibly being too small to shift my boat which is a 5.8m northcraft without screaming it tits off all the time.

Or should I look for something around the 115 mark and hope for a larger engine that won't have to work so hard thus being hopefully better on fuel.

Any opinions or help would be appreciated thanks Ross....
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Old 12 September 2014, 16:54   #2
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Would it take a DF140? They don't use anywhere near as much fuel as your old carbed monster.
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Old 12 September 2014, 17:09   #3
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Originally Posted by Nos4r2 View Post
Would it take a DF140? They don't use anywhere near as much fuel as your old carbed monster.
Just don't want a engine that's big like a 140 and not be used so I'm carting around extra weight.
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Old 15 September 2014, 08:17   #4
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Re. the weight thing you need to check multiple manufacturers - a given horsepower of engine will share the main lumps of hardware with one or two other HP variants.(probably more at the 3 figure HP end of the range).

Net result is you could have ,say an incredibly heavy 70Hp from Manufacturer A, whereas the 70 form Manufactureer B makes revery other 70 look lardy.
A's engine is a de-tuned 90/ 100 lump, wheras B's is de- tuned to be the 60 & the 50.


So as you are looking in the 90-135 range you may find someone's 130 is not a lot heavier than someone else's 90.....


As for fuel consumption have a search on here - the general average regardless of engine size or strokes appears to be about 1 L/mile. Yes if you do a lot of low speed / idle work (e.g fishing) then go fuel injected 4- stroke. If you blat along at WOT all day at WOT then it's a case of if you need the gee gees you need to burn the fuel!
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Old 15 September 2014, 08:40   #5
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You wont go far wrong with an Optimax.

My 150 is very frugal -Cruise at 35Kts and 3700 rpm gives around 1.2Nm/l ticking over at 6 kts it does around 8Nm/l - these are the figures from a few weeks ago when we had at least 200Kg of chain and anchors in the boat mark laying at Dartmouth.

But if you're looking for something smaller, the 115Hp Optimax might do, it its pretty light at 160Kg.
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