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Mercury 50 hp 2007 4 stroke troubleshoot

F

Figure855

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My engine has 1700 hours. Been a good motor. Right now it hesitating when I throttle up. Ex. 3000 to 4000 rpm's. When it get to the higher rpm, it runs smooth. It has new plugs, fuel filters, fuel pumps check out ok, checked the coils and wires. It just wants to sputter when giving it gas. Any ideas? Thankss
 
Inspect all lines for any signs of wear, esp cracks. Vacuum leaks can inhibit the response time, once a good fuel/air equilibrium is achieved the motor will run fine, but initially it is deprived due to the vacuum imbalance caused by a cracked or poorly connected line.
Mike
 
I'm still fighting this problem. I know it is now a fuel issue. Mechanic has had motor on computer and all checks out. Still want to bog down when giving it gas. Will then run ok at new rpm, but will eventually completely shutdown. Prime bulb and runs again for awhile. I check screens and everything on the tank including new fuel line. Also eliminated the tank and used another. Nothing changed. This problem has to be within the motor. Any ideas. New in motor are plugs, filters, IAC valve and thermostat.
 
Could be the lift pump not getting enough volume to VST. I've heard of aftermarket pumps doing this and is not something that is not immediately apparent, like if you can see the supply reaching the VST, but it's actually less than it should be under vacuum. I know you mentioned everything checks out, but it might be difficult to nail down, more subtle than you realize. Have you ran some injector cleaner through the system yet? Any fuel not completely purged from the system will age over winter and can sometimes have a lasting effect in the injector components.
 
siluetae137 said:
Could be the lift pump not getting enough volume to VST. I've heard of aftermarket pumps doing this and is not something that is not immediately apparent, like if you can see the supply reaching the VST, but it's actually less than it should be under vacuum. I know you mentioned everything checks out, but it might be difficult to nail down, more subtle than you realize. Have you ran some injector cleaner through the system yet? Any fuel not completely purged from the system will age over winter and can sometimes have a lasting effect in the injector components.
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