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I Love microskiff.com!
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Discussion Starter · #1 ·
I have a 150 hp yamaha v max carbed and it surges @ high speed bad, it also now starts like a efi with no choking necessary. I see alot of gas film on the water. I did a compression test with 110 across the board. A a fuel pump pressure of 4.5 lbs on both.
 

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90 Posts
I'd check the fuel pumps again. Unbolt them from the block and pump the primer, if any fuel comes out of the engine side of the pump the diaphragms are shot. A bad FP diaphragm can make you run rich at idle and lean on the top end, just as you described. [smiley=2cents.gif]
 

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Brandon, FL
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11,119 Posts
Ethanol is not the root of all engine problems. Most likely it is the years of use that simply deteriorated the seals and gaskets.
 

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If you are running ethanol I'm sure it contributed, if in fact your fuel pumps were the source of your problems. ETOH is hard on rubber parts.
 

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Cert. Yamaha technician
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4,330 Posts
Ok. If your fuel pump diaphrams are white, they are mylar and most likely your problem, the updated ones are black and made of neoprene. Or.. Another syptom of your problems is a stuck float or a "sink" (a float with a hole in it that doesnt, well float lol)
 
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