Suzuki PU140 1991 Stalling out?

Suzu140pump

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Dec 26, 2018
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My 1991 Suzuki PU140 (DT140 with a jet pump vs a propeller) will plane out at 4600 rpm and run fine at that speed. However, when I increase throttle to 5100 rpm the motor starts stalling out and changes from 4600 to 5100 to 4600 to 5100. When I decrease throttle back to 4600 rpm the motor runs fine on plane.
Background: The motor has acted this way since I changed fuel tanks. The current tank is a plastic 12 gallon Spectra. I have checked all hose clamps along the fuel line and all are tight. Any suggestions as to why this 1991 Suzuki PU140 is acting up would be appreciated.
 

saltchuckmatt

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Jul 19, 2019
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My 1991 Suzuki PU140 (DT140 with a jet pump vs a propeller) will plane out at 4600 rpm and run fine at that speed. However, when I increase throttle to 5100 rpm the motor starts stalling out and changes from 4600 to 5100 to 4600 to 5100. When I decrease throttle back to 4600 rpm the motor runs fine on plane.
Background: The motor has acted this way since I changed fuel tanks. The current tank is a plastic 12 gallon Spectra. I have checked all hose clamps along the fuel line and all are tight. Any suggestions as to why this 1991 Suzuki PU140 is acting up would be appreciated.
Possibly the fuel line diameter?
Would seem to be starving for fuel.
 

Suzu140pump

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Dec 26, 2018
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I agree with the starving for fuel, but the fuel line, engine connection and line to the fuel pump are all stock. The problem started with the fuel tank change. Unfortunately, the plastic, 12 gallon, portable tank has to be of specific dimensions to fit in the Sea Ark compartment. There may be an issue with the fuel tank's anti-siphon valve design. So, I think I need to run the motor using another portable fuel tank to eliminate any tank issues. Thanks for your response!
 

99yam40

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Sep 7, 2008
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might try putting a clear line on the output of the fuel pump just to see if air bubbles are showing up in the fuel stream indicating sucking air into the system.
also monitor fuel pressure out of the pump to see if it drops

some shops should have a system to measure the fuel flow to see if it meets what is needed for the motor
 

Suzu140pump

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Dec 26, 2018
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Thank you. I will try the clear line suggestion. If nothing develops, I will move on to the fuel flow.
 

Suzu140pump

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Dec 26, 2018
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I looked at the line between the fuel pump and carborators as it disappears behind the oil tank. That would be a major under taking at this point. So I will find a smaller portable fuel tank and see if it runs the same. Thank you for your suggestion.
 

Suzu140pump

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Dec 26, 2018
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Took the boat out with fuel line stuck in a 5 gallon gas can with 4 gallons of gas. I secured the line so that it didn't move around in the gas can. Unforyunately, there was no change in motor performance, so I have eminated the fuel tank as the problem.
 

Ironhorse2022

Seaman Apprentice
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Oct 14, 2022
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47
Probably a reach but I’ve heard of old rubber fuel lines getting soft and collapsing under high fuel demand. Perhaps after warming up the engine, connect a new section of fuel line (without bulb) and run it into your fuel tank and see what happens. I think you’ve already ruled out a gas cap venting problem (partially blocked). Also, I wonder if perhaps your fuel pump is struggling to deliver max flow ? I realize none of these correlate to switching your tank out Which may just be a coincidence. Good luck.
 

Suzu140pump

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Thank you for your time and suggestion!! The fuel line between the tank and motor is brand new.
It was suggested "off line" to slightly adjust the air/fuel screw on each of the 4 carbs (that I call 4 gas guzzlers). The manual says to adjust those screws 1.125 to 1.625 turns. So, should the wind in Burbank, WA ever die down we will try this. Thanks again.
 

saltchuckmatt

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Jul 19, 2019
Messages
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Thank you for your time and suggestion!! The fuel line between the tank and motor is brand new.
It was suggested "off line" to slightly adjust the air/fuel screw on each of the 4 carbs (that I call 4 gas guzzlers). The manual says to adjust those screws 1.125 to 1.625 turns. So, should the wind in Burbank, WA ever die down we will try this. Thanks again.
Shouldn't change your WOT just ideling circuits. Fuel lines under the cowl is a good suggestion.
 
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