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Old 27 February 2009, 18:21   #1
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90hp carbed and optimax weight difference

I've been looking at 90hp carb 2-stroke mecury and 90hp optimax engines and the weights are 300 and 370lb respectively! Thats a hefty difference for the optimax but not entirely sure why? Surely this weight difference is going to have a fairly significant negative effect on the extra fuel efficiencey gained from having an optimax over a carb engine? I've read the optis have a 1.5litre block, does the carb model have a 1.3 litre block?

Is an optimax worth it over an equivalent carb model considering the extra cost, weight and complexity?
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Old 27 February 2009, 18:41   #2
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given up on the twatsoo already???
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Old 27 February 2009, 18:54   #3
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na not quite yet (going to tackle the bolts next week) but I am possibly considering upgrading anyway...
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Old 01 March 2009, 03:51   #4
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Think you will find about 1/3rd fuel saving regardless of the extra weight. Carb weights 139kg Opti is 163kg. So its the same as putting a 25 ltr fuel can at the back of the boat.

The Carb is a 1.3ltr but the older "clam shell" models were 1.1ltr blocks.
The weight probably comes from the bigger block, alternator, comprssor, etc etc. Its worth it for the fuel saving, but you will probably find you might loose some grunt as Carb engines are usually rated at above there hp rating Merc 90's usually run at about 94hp, were as the Opti will be bang on 90hp.
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Old 01 March 2009, 13:41   #5
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Thanks, thats interesting, especially about the slight difference in power.
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Old 01 March 2009, 14:31   #6
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Of course the newer injected 90HP Tohatsu is a great engine, and might require less work to fit on your boat thats set up for the older Tohatsu.

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Old 01 March 2009, 15:18   #7
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yeah that is a perfect choice of engine for me but they rarely come up second hand, if at all and I can't afford a new one (although they are a really good price new, about 4700!)
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