I had a similar problem once that turned out to be a collapsing fuel line
when the need for gas was greater. I replaced the fuel line and it was
cured.




"Grant" wrote in message
ups.com...
Hello,

I bought a used Whaler with a 2004 70 HP Yamaha outboard. I used it in
last fall and again this spring on local lakes. It ran fine.

It recently developed a problem which I'll describe. I'm looking for
advice as to where the problem might be.

I took it out yesterday and ran it at around 14K RPM out of the local
harbor. I then accelerated up to around 40K RPM and it did fine. I
slowed back down to around 14K RPM for around 10 minutes and then when
I tried to accelerate the RPMs actually decreased as I tried to give it
more gas to the point where the engine would stall if I gave it too
much. If I backed off the accelerator it would return to around 14K
RPM.

It I shifted into neutral and accelerated I could run it up to 40K RPM
without problem. However, doing the same when in gear would cause the
problem.

I played with it for a while as I slowly motored back to port and
noticed that the RPMs seemed to be increasing. Sure enough, easing the
throttle up it went right up without any stall. I zoomed back to the
harbor and slowed down again as I entered and then as a test tried to
accelerate again and sure enough the problem was back.

So, someone suggested that I check my fuel filter to see if I had water
in it but it doesn't appear that I do. I had the whole fuel line
flushed and the external filter was replaced as part of that fix up
about 3 weeks ago. I had used the boat at high speed 3 or 4 times
since without problems.

Thanks!

Grant Schenck