JR North wrote:
Your prop hub is slipping. Get the prop rebuilt.
JR
BTDT got the T-shirt, too

Mike Slater wrote:

I was cruising along in my 24ft pontoon boat when I got a real
surprise. Somebody please tell me how and why I could be running wide
open throttle at my normal 5500 rpm and then suddenly the boat took
off like a bat out of hell running at 8000 rpms and 25mph??? I never
touched the throttle. It has never run that fast ever. After about 2
minutes it went back down to 5500 and never did 8000 again. Its a
60hp mercury Bigfoot outboard. It has never done this before and I
don't even know how it could rev that high and go 25mph. Normal is
5500 and 17mph. What happened??

Mike


The boat wouldn't go faster if the prop was spun.

"Mike Slater" wrote in message
news:knfZl.742458$yE1.158636@attbi_s21...
I was cruising along in my 24ft pontoon boat when I got a real surprise.
Somebody please tell me how and why I could be running wide open throttle
at my normal 5500 rpm and then suddenly the boat took off like a bat out of
hell running at 8000 rpms and 25mph??? I never touched the throttle. It
has never run that fast ever. After about 2 minutes it went back down to
5500 and never did 8000 again. Its a 60hp mercury Bigfoot outboard. It
has never done this before and I don't even know how it could rev that high
and go 25mph. Normal is 5500 and 17mph. What happened??

Mike
I wanted to try to close the loop on this issue and I think I can. I think
as someone stated, running "lean" can cause the engine to rev higher. I
looked at my inline fuel filter and the thing was empty when it did it
again. Today I replaced all the fuel lines to make sure no air was getting
in and it has not happened since. I am back to 17mph. BTW, I don't trust
the tach reading of 8,000 that I got because the reading is a little
"unsteady" despite no discernable (by ear) engine rpm changes.

I know that running lean can burn the pistons so whoever mentioned running
out of fuel (lean) as being something to check... THANKS.

Mike