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Old 02-24-2013, 09:38 PM   #1
Sam
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Need help with Gen troublshooting

So, I am helping a friend on his Sea Ray. His Generator is a Mercury 4 cylinder. It it has a Carburetor and the motor is constantly flooding. Here are some known facts:

1. New carb.
2. Raw gasoline gurgling and pooling outside of #4 EXHAUST manifold
3. Good spark on all cylinders
4. 180 PSI on ALL cylinders
5. Larger after market fuel pump, but adjusted to 1lb psi of fuel pressure via
a regulator. Still same problem.
6. Needle and seat seem to be fine (new carb) and floats are parallel to carb
body.

The most significant question is this. Why would raw fuel accumulate and pool out of the exhaust manifold????? With 180PSI indicated, could the exhaust valve still be stuck? Why is it being pumped out at the exhaust manifold gasket and not out into the river? Back pressure?

Sure, the exhaust manifold gasket is shot, but why the raw fuel on #4?

Any help or previous experience would be appreciated.

Thanks,

sam nigro
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Old 02-24-2013, 09:54 PM   #2
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Sounds like the float, needle, seat to me.
There would be a riser in the exhaust system so liquid in the manifold would stay there (or leak out a bad gasket.
Try this, install a shut-off in the gas line. Fill the bowl. Shut the valve. Run the engine. Does it run fine until the bowl is empty? If it does, you had a float problem.
Don't blow up the boat.
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Old 02-24-2013, 09:58 PM   #3
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OK, what is a riser?
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Old 02-25-2013, 07:41 AM   #4
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Are you sure he doesn't have a leak on the intake gasket? Maybe the gas is never reaching the cylinder.
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Old 02-25-2013, 08:08 AM   #5
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Quote:
Originally Posted by Brooksie View Post
Try this, install a shut-off in the gas line. Fill the bowl. Shut the valve. Run the engine. Does it run fine until the bowl is empty? If it does, you had a float problem.

Don't blow up the boat.
Two really good pieces of advice here.
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Old 02-25-2013, 09:43 AM   #6
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OK, what is a riser?
Riser= A place, downstream of the manifold, where the pipe rises then falls to keep cooling water injected in the exhaust from coming back in the manifold.
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Old 02-25-2013, 01:34 PM   #7
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Thanks for the confirmation as to the definition of riser.

Also, yes the gasoline pooling IS on the exhaust side and IS leaking out from between exhaust manifold and the head. So very bizarre to me.
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Old 02-25-2013, 04:53 PM   #8
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Also, yes the gasoline pooling IS on the exhaust side and IS leaking out from between exhaust manifold and the head. So very bizarre to me.
Yes, it is pretty bizarre. Perhaps it's just the combination of a bad manifold gasket and unburned fuel from the flooding.

But at the risk of stating the obvious, you need to nail down the source of the over-fueling first, and something not right in the float mechanism still seems the most probable cause. I like the idea of cutting of the fuel entering the float to see if it runs OK until the float empties. That would isolate the problem to the carb/float.

Have you had the carb apart and tested the float valve to confirm it's sealing off completely? Gently blowing on the fuel inlet while manipulating the float will confirm. It should seal off completely.

Is the genset installed level in the boat? If it's off level, the float might need adjustment to compensate. Just a thought.

What's the level of the fuel in the tank relative to the float? Even though you have the pump dialed down, head in the fuel supply will add about 1/2 PSI per foot (actually a little less, but that's close enough). If you can put a gauge on the fuel line at the carb you could confirm that part is doing what you expect.
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Old 02-25-2013, 07:42 PM   #9
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Yes, I aggree with the float needle valve/seat accessment. The float will have a measurement spec as to what is correct as to level. Adjustments are made by gently bending the float where it contacts the needle. But that being said, it all is based on the float 'floating' at the correct height. Long ago in my hazy early years floats were made of plastic, and some of those plastics didn't do well in ethanol laced gas. They would absorb gas/alcohol and float low flooding the engine. By now the evil effects of ethanol have been nearly or completely mitigated, but there should be a spec for the float weight. Even brass can leak.
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Old 02-25-2013, 08:06 PM   #10
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Originally Posted by Sam View Post
So, I am helping a friend on his Sea Ray. His Generator is a Mercury 4 cylinder. It it has a Carburetor and the motor is constantly flooding. Here are some known facts:

1. New carb.
2. Raw gasoline gurgling and pooling outside of #4 EXHAUST manifold
3. Good spark on all cylinders
4. 180 PSI on ALL cylinders
5. Larger after market fuel pump, but adjusted to 1lb psi of fuel pressure via
a regulator. Still same problem.
6. Needle and seat seem to be fine (new carb) and floats are parallel to carb
body.

The most significant question is this. Why would raw fuel accumulate and pool out of the exhaust manifold????? With 180PSI indicated, could the exhaust valve still be stuck? Why is it being pumped out at the exhaust manifold gasket and not out into the river? Back pressure?

Sure, the exhaust manifold gasket is shot, but why the raw fuel on #4?

Any help or previous experience would be appreciated.

Thanks,

sam nigro
doesn't make sense. First guess is the float level is wrong and this can take out the engine f run that way. No way can gas be leaking out of the exhaust manifold unless tons of gas is flooding the engine and its being pumped there by the piston. If that's the case the engine cylinders will be scored from the gas washing off the oil. That has happened to me in the past. I fixed the problem with a beer carton by making a gasket which i put under the needle valve in the carburetor so it would be higher cutting off fuel earlier and that repaired the problem. I then had to tear down the engine and put new rings in and hone the cylinders
I'll bet there is gas in your oil as well?
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Old 02-25-2013, 08:54 PM   #11
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Brit, I think your close to hitting the nail on the head. In looking at a manual that I found, the writer was adamant "do not use increased fuel pressure from pump" I believe that many things are at play here including hydaulic action acting on the fuel in in the #4 cylinder. We ordered new gaskets and checking on the fuel pressure issue as well as the float/needle and seat adjustments. I want to thank all of you for your kind advice.

sam nigro
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Old 02-25-2013, 11:08 PM   #12
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Brit, I think your close to hitting the nail on the head. In looking at a manual that I found, the writer was adamant "do not use increased fuel pressure from pump" I believe that many things are at play here including hydaulic action acting on the fuel in in the #4 cylinder. We ordered new gaskets and checking on the fuel pressure issue as well as the float/needle and seat adjustments. I want to thank all of you for your kind advice.

sam nigro
Restitution
Your welcome Sam. I just hope you havent damaged your engine
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Old 02-26-2013, 06:43 AM   #13
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My guess would be heat.

A needle and seat can only hold 5-7 psi .

On shut down I guess the fuel in the feed line gets warm from the engine , expands (perhaps vaporizes) and creates pressure the carb isnt built to handle.

Many noisemaker builders install an electric solenoid valve that keeps the carb isolated from the fuel supply line on shutdown.
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Old 02-26-2013, 07:14 PM   #14
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My guess would be heat.

A needle and seat can only hold 5-7 psi .

On shut down I guess the fuel in the feed line gets warm from the engine , expands (perhaps vaporizes) and creates pressure the carb isnt built to handle.

Many noisemaker builders install an electric solenoid valve that keeps the carb isolated from the fuel supply line on shutdown.
Hasnt this boat operated for years with the generator without problems? If so its not likely what you envision unles modifications were made that deviated from the manufacturers original layout
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Old 03-03-2013, 04:48 PM   #15
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Or something has recently quite working properly. Maybe there is a shutdown solenoid/device such as FF suggested but it has quit working.
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Old 03-05-2013, 07:34 PM   #16
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Or something has recently quite working properly. Maybe there is a shutdown solenoid/device such as FF suggested but it has quit working.
i got a cat like that
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