Hi everyone,
With the wealth of knowledge and experience here, I have a problem that
needs your insight.

My (new to me) Yamaha 9.9 HP outboard (built year 2000) usually runs
fine at lower RPM, but when I ramp up over 35% of max speed the engine
will invariably run fine for 20-40 seconds and then cough, sputter, slow
for a few seconds and then speed back up. The faster the RPM, the more
frequent the problem.

Sometimes pumping the sqeeze bulb on the fuel line will solve the
problem for a short while, but not always.

I immediately suspected a fuel line problem, but the filters are all
clean (in engine and in gas tank), the hose seems to be clear, and just
to make sure I also changed the spark plugs and oil.

The only think I can think of is that it could be sucking air somehow.

Any suggestions would be extremely welcome!

Thanks, and fair winds,
Mike

On Tuesday 20 July 2004 8:19 pm in rec.boats.cruising
wrote:

My (new to me) Yamaha 9.9 HP outboard (built year 2000) usually runs
fine at lower RPM, but when I ramp up over 35% of max speed the engine
will invariably run fine for 20-40 seconds and then cough, sputter, slow
for a few seconds and then speed back up. The faster the RPM, the more
frequent the problem.

Sometimes pumping the sqeeze bulb on the fuel line will solve the
problem for a short while, but not always.

Sounds like a blocked tank breather to me.
On small outboards the breather is often a small hole in the fuel filler
cap. If this is blocked or if you have the wrong fuel cap there will be
a vacuum in the tank as fuel is pumped out into the engine.
The simple test for this is to loosen the filler cap.
Some tanks have a finger screw on the cap which you need to open when
running the engine.


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Sounds like a weak fuel pump or a sticking needle and seat in the carb.

Dennis

Hi everyone,
With the wealth of knowledge and experience here, I have a problem that
needs your insight.

My (new to me) Yamaha 9.9 HP outboard (built year 2000) usually runs
fine at lower RPM, but when I ramp up over 35% of max speed the engine
will invariably run fine for 20-40 seconds and then cough, sputter, slow
for a few seconds and then speed back up. The faster the RPM, the more
frequent the problem.

Sometimes pumping the sqeeze bulb on the fuel line will solve the
problem for a short while, but not always.

I immediately suspected a fuel line problem, but the filters are all
clean (in engine and in gas tank), the hose seems to be clear, and just
to make sure I also changed the spark plugs and oil.

The only think I can think of is that it could be sucking air somehow.

Any suggestions would be extremely welcome!

Thanks, and fair winds,
Mike

Another possibility is bad gas, being either old or contaminated. Try a
fresh tank.

Sherwin Dubren

" wrote:

Hi everyone,
With the wealth of knowledge and experience here, I have a problem that
needs your insight.

My (new to me) Yamaha 9.9 HP outboard (built year 2000) usually runs
fine at lower RPM, but when I ramp up over 35% of max speed the engine
will invariably run fine for 20-40 seconds and then cough, sputter, slow
for a few seconds and then speed back up. The faster the RPM, the more
frequent the problem.

Sometimes pumping the sqeeze bulb on the fuel line will solve the
problem for a short while, but not always.

I immediately suspected a fuel line problem, but the filters are all
clean (in engine and in gas tank), the hose seems to be clear, and just
to make sure I also changed the spark plugs and oil.

The only think I can think of is that it could be sucking air somehow.

Any suggestions would be extremely welcome!

Thanks, and fair winds,
Mike

Thanks everyone! The gas was new last weekend, so I don't think that's
the problem. I'll check the other things when I get back into town
tomorrow.
Thanks again,
Mike

wrote:

Hi everyone,
With the wealth of knowledge and experience here, I have a problem that
needs your insight.

My (new to me) Yamaha 9.9 HP outboard (built year 2000) usually runs
fine at lower RPM, but when I ramp up over 35% of max speed the engine
will invariably run fine for 20-40 seconds and then cough, sputter, slow
for a few seconds and then speed back up. The faster the RPM, the more
frequent the problem.

Sometimes pumping the sqeeze bulb on the fuel line will solve the
problem for a short while, but not always.

I immediately suspected a fuel line problem, but the filters are all
clean (in engine and in gas tank), the hose seems to be clear, and just
to make sure I also changed the spark plugs and oil.

The only think I can think of is that it could be sucking air somehow.

Any suggestions would be extremely welcome!

Thanks, and fair winds,
Mike

I had a similar problem on a different engine the weekend before last. I had
to keep pumping the bulb to limp back to port. The problem was the fuel
pump. An $11 rebuilt kit fixed the problem.

Tom

wrote in message
. ..
Hi everyone,
With the wealth of knowledge and experience here, I have a problem that
needs your insight.

My (new to me) Yamaha 9.9 HP outboard (built year 2000) usually runs
fine at lower RPM, but when I ramp up over 35% of max speed the engine
will invariably run fine for 20-40 seconds and then cough, sputter, slow
for a few seconds and then speed back up. The faster the RPM, the more
frequent the problem.

Sometimes pumping the sqeeze bulb on the fuel line will solve the
problem for a short while, but not always.

I immediately suspected a fuel line problem, but the filters are all
clean (in engine and in gas tank), the hose seems to be clear, and just
to make sure I also changed the spark plugs and oil.

The only think I can think of is that it could be sucking air somehow.

Any suggestions would be extremely welcome!

Thanks, and fair winds,
Mike

Thanks everyone! The gas was new last weekend, so I don't think that's
the problem. I'll check the other things when I get back into town
tomorrow.
Thanks again,


Mike,
When you speed up the motor, does applying a little choke let it go to
higher RPM's? I had this problem a couple times as the motor sits on the
pushpit most of the time and what is left in the carburator gums it up. I
always turn the gas off and run it till it quits, but after a few months the
problem is back again.

Leanne

Leanna,
I thought of using the choke too, and tried it last night. It didn't do
any good. But it could be that the carb is gummed up. I'll add that to
my list of things to check.
Thanks!

Leanne wrote:

Thanks everyone! The gas was new last weekend, so I don't think that's
the problem. I'll check the other things when I get back into town
tomorrow.
Thanks again,



Mike,
When you speed up the motor, does applying a little choke let it go to
higher RPM's? I had this problem a couple times as the motor sits on the
pushpit most of the time and what is left in the carburator gums it up. I
always turn the gas off and run it till it quits, but after a few months the
problem is back again.

Leanne

On Wed, 21 Jul 2004 12:06:32 GMT, "
wrote:

Thanks everyone! The gas was new last weekend, so I don't think that's
the problem. I'll check the other things when I get back into town
tomorrow.
Thanks again,
Mike

Another possibility which happened to my four-stroke Honda 9.9 is a
stuck carb float, which make for harder starts, limited acceleration
and the occasional stall. It needed a good clean due to crap in the
gas.

Filtering the gas/cleaning the tank is always a good idea.

R.

Thank you, everyone! The problem was a plugged vent- I got it cleared
last night and ran it smoothly for 15 minutes.
Mike

wrote:

Hi everyone,
With the wealth of knowledge and experience here, I have a problem that
needs your insight.

My (new to me) Yamaha 9.9 HP outboard (built year 2000) usually runs
fine at lower RPM, but when I ramp up over 35% of max speed the engine
will invariably run fine for 20-40 seconds and then cough, sputter, slow
for a few seconds and then speed back up. The faster the RPM, the more
frequent the problem.

Sometimes pumping the sqeeze bulb on the fuel line will solve the
problem for a short while, but not always.

I immediately suspected a fuel line problem, but the filters are all
clean (in engine and in gas tank), the hose seems to be clear, and just
to make sure I also changed the spark plugs and oil.

The only think I can think of is that it could be sucking air somehow.

Any suggestions would be extremely welcome!

Thanks, and fair winds,
Mike