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mariner 50 hp 1991 fuel mixture screw adjustment

S

swarf

New member
hi, my 2 stroke 50 hp 1991 is using more fuel since someone adjusted the fuel mixture screw for me, I wasn't watching while he did it so don't know where it is to adjust back, it used to do 5mpg but is now doing 3.5mpg with the same top end speed. can someone tell me where it is and how far I should unscrew it from all the way in. thanks.
 
Those idle mixture screws have nothing to do with your on-plane gas mileage. Look for something else, like crud on the hull, bent prop, etc.

Jeff
 
the hull and prop are ok, so what does the fuel mixture screw do? does it only adjust the mixture on tickover, because the economy is worse since he adjusted it.
 
hate to ask such an obvious question, but is the hull clean? Normal marine growth on the bottom, especially towards the end of the season, can create a lot of drag.
 
the hull is clean because the boat is left on a trailer when not in use, is 3.5mpg the normal usage for a 50hp 2 stroke pushing a shetland 535, perhaps I think theres a problem when there isn't one.
 
I'm not an expert but I can tell you from experience that two stroke outboards are NOT known for good gas mileage. I have a 115 HP on a 18 ProCraft and I'll burn 20 gallons or better in an 8 hour day of hard fishing. I've never figured the actual mpg, but I can tell you it's not good. How are you figuring "miles traveled" since boats don't have odometers? Don't take it the wrong way but are you sure you're calculations are correct?
 
I imagine it would be difficult to know that you are boating in the same conditions each time you go out. Current, wind, swell, direction of travel, etc would all impact on fuel economy or lack of it. Could it be that your engine is fine and that other factors are causing the differences? Just food for thought.
 
I have a gps to measure the milage so I know thats right, perhaps I just need to buy a bigger fuel tank then I won't have to keep filling it up so often.
 
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