sx250z

[Captain Bill]

I had a problem with a sx250Z kicking out at 3500 RPM’s I did the obvious and still had the problem. I took it to a repair shop that had the tools and harness to find the problem. They did and it was a diaphragm in a fuel pump in the low pressure line.
That’s the good part the bad is the bill was230 dollars and the boat was down for two weeks.
The old diaphragm had what looked like a hot spot where it is discolored and very brittle.
I can not enclosed a picture untill I find out how, but would ask if any one would know what would cause this.
Where is the best place to get a mity vac 90890-06756
Is fuel pumpdiaphragm cracking some thing that happens a lot.

[boats.net]

The diaphrams in your motor were probably the new clear plastic looking diaphram which Yamaha upgraded to because of the alcohol and ethanol blended fuels. They don't seem to last as long as the older rubber diaphrams. They need to replaced every couple of years as part of your normal maintenance.