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Mercruiser 50L High RPM Problems

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skiddley

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"Hello, I have a 1988 Mercruis

"Hello, I have a 1988 Mercruiser 5.0 Liter engine. When I disengage the propeller, I can raise the RPM's to 4000+ No Problem. When there is a load on the engine and propeller is engaged I can cruise at 2000 RPM. When I get between 2500 to 4000 RPM, the engine bogs down and sometimes stalls completely. The engine backfires at times also. I changed the fuel filter, plugs, distibutor cap & rotor, ignition sender, adjusted the timing and all of this did not solve the problem. Please Help. Thanks"
 
"HI,i would check fuel pressur

"HI,i would check fuel pressure and flow,for a start.then u could put the timing light back on and run it up and c if the spark advances smoothly and stays in one spot.Does the temperature of the engine alter?"
 
"Thank You for your responses.

"Thank You for your responses. I have rebuilt the carb, the timing is set and advances fine. I had the gas tank empty and out of the boat indoors durring the winter while I remodeled the interior (maybe rust in the tank?)if so how do I clean the gas tank?
I had an issue prior to this incedent where I had gas spill out of the vent hole while filling the tank. I was advised to put a 360 degree loop in the vent for the gas tank so gas would not spill out of it anymore, which I did. Would this be the reason for my problem? Not enough air comming into the tank for the fuel going out?"
 
"hi,i would disconnect the coi

"hi,i would disconnect the coil,put a T in the fuel line between pump and carbie,and check fuel pressure with a gauge,then see how quickly the pressure drops off when cranking stops.if it goes down quickly,rebuild fuel pump.then u can do a flow check.[if uve got an electric fuel pump,all the better].you should get a constant stream of fuel,of at least 15 sec duration.if it dribbles to a stop quickly,take the gas tank cap off and c if that helps. try that. 3.50 pm fri"
 
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