[jeff_erickson]

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.

 

[Brett]

Fuel feed would be my first guess.
Checked your plugs to see if you're running rich?

 

[twitch]

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]

 

[jeff_erickson]

Thanks, I think I will rebuild both pumps to be on the safe side. Cheap fix for a 2005 engine

 

[jeff_erickson]

Do you think ethanol might have caused the trouble?

 

[DuckNut]

Ethanol is not the root of all engine problems. Most likely it is the years of use that simply deteriorated the seals and gaskets.

 

[twitch]

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.

 

[cutrunner]

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)

 

[jeff_erickson]

I replaced both fuel pumps and it runs like new! Thanks

 

[twitch]

Glad ya got it fixed.