2004 Yamaha 60Hp 2-stroke issues

USMC-Mustang

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I have a 2004 Yamaha 60HP 2-stroke on a 16' war eagle. Recently it started idling rough and acting sluggish at low speeds. Once I get past quarter throttle response and performance is fine. It's not very responsive the first quarter throttle and sounds really rough. I run it every weekend and it just started last week. Troubleshooting steps that I've completed thus far:

- I took a fuel sample and there was no water

- I added a water separator.

- I keep Marine Sta-Bil in my tank.

- 2 cycle fluid is being injected.

Any ideas? Many thanks.

Dave
 

robert graham

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Re: 2004 Yamaha 60Hp 2-stroke issues

The fuel pump may have a hole in the diaphragm causing raw fuel to get sucked into that cylinder causing a very rich mixture....check plugs for fuel wetting/fouling. Remove filter with 2 screws while leaving it hooked up, then pump primer bulb and check for fuel coming out of that back side port/hole....pump is about $50 and very easy to replace. If pump is O.K. Then maybe carbs/jets are dirty and need removal/cleaning....good luck!
 

USMC-Mustang

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Re: 2004 Yamaha 60Hp 2-stroke issues

Pulled, cleaned and checked gaps. Ran for a few minutes then pulled them again. A little wet but not bad
Cleaned fuel filter. It was clean.

Not sure what you mean about two screws. One bolt is holding on the fuel filter.

image1408.jpg



Many thanks for responding.
 
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boscoe99

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Re: 2004 Yamaha 60Hp 2-stroke issues

Sounds to me like the idle/low speed fuel circuit may be clogged with some debris.

I think he meant two bolts holding the fuel pump in place.

 
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USMC-Mustang

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Re: 2004 Yamaha 60Hp 2-stroke issues

At idle I pulled the spark plug wires off, one at a time. Cylinders one and two had a noticeable rpm change and when I pulled three nothing happened.

Swapped coil, wire and plug and the issue is still with the third cylinder. Pulled the plug and lest it out with the wire hooked up and it's getting spark.

Where do I check the low speed fuel circuit?
 
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robert graham

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Re: 2004 Yamaha 60Hp 2-stroke issues

Yep, I meant those 2 10mm hex bolts holding on the Pump, not the filter...it's any easy item to check/ replace....
 

USMC-Mustang

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Re: 2004 Yamaha 60Hp 2-stroke issues

The fuel pump may have a hole in the diaphragm causing raw fuel to get sucked into that cylinder causing a very rich mixture....check plugs for fuel wetting/fouling. Remove filter with 2 screws while leaving it hooked up, then pump primer bulb and check for fuel coming out of that back side port/hole....pump is about $50 and very easy to replace. If pump is O.K. Then maybe carbs/jets are dirty and need removal/cleaning....good luck!

Did this with pump. When I pumped the bulb a small stream of fuel comes out of the bottom bolt hole (that holds it on).
 

robert graham

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Re: 2004 Yamaha 60Hp 2-stroke issues

Your pump may be nearly 10 years old(if it's never been changed), so it may be time....
 

USMC-Mustang

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Re: 2004 Yamaha 60Hp 2-stroke issues

Ok. I will find one tomorrow.

Just to clarify, fuel coming out of the back of the pump when priming is a sign of pump failure or does this indicate normal operation?

Would that be what's causing issues with that #3 cylinder?

Many thanks for your time and patience with my questions.

Dave
 
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robert graham

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Re: 2004 Yamaha 60Hp 2-stroke issues

You'll notice that the fuel pump is mounted to the side of the crankcase where a small hole or port uses crank vacuum/pressure to actuate a small Mylar/plastic diaphragm in the pump....they do fail with time....I replaced the fuel pump on my 90HP Yamaha after about 10 years while it was still working...kept the old one for a spare....
 

robert graham

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Re: 2004 Yamaha 60Hp 2-stroke issues

A bad diaphragm will give you a fuel rich/plug fouling condition....may be your problem...
 

99yam40

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Re: 2004 Yamaha 60Hp 2-stroke issues

Ok. I will find one tomorrow.

Just to clarify, fuel coming out of the back of the pump when priming is a sign of pump failure or does this indicate normal operation?

Would that be what's causing issues with that #3 cylinder?

Many thanks for your time and patience with my questions.

Dave

Yes, fuel leaking out of pulse port is a sign of failure.
Not sure if fuel coming out of bolt hole is the same thing though.
You can take pump apart and inspect the diaphragms for holes/tears

Since the #3 crankcase is the one that furnishes the pulses to operate the fuel pump,
that is the cylinder that gets too much fuel when it leaks and will not fire properly.
The leaking fuel can cause the oil to be washed off of the cylinder walls and maybe even the bearings causing failures if run too much like that
 
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USMC-Mustang

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Re: 2004 Yamaha 60Hp 2-stroke issues

Took it to an outboard mech and he disassembled the carbs and thoroughly cleaned them. All three were in rough shape and the port in the small jet on the bottom carb was completely clogged.

Learned a lot as I sat there and watched him work.

Thanks for the responses.
 
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