mercruiser 5.7 350/260hp alpha one outdrive starting issues

[capt.snappy1]

83' mercruiser 350/260hp alpha one outdrive with rochester quadrajet carburetor. replaced mechanical fuel pump.engine started and was run for about 10 minutes. several days later engine would not start so replaced carburetor. boat still failed to start except briefly on starter fluid checked fuel flow up to carburetor and is good.changed fuel filter and checked fuel and seemed
clean and not phase seperated. engine still refuses to start except briefly. ideas? thanks in advance!

 

[alldodge]

Start by verifying spark, use a spark tester to verify length and color

Is the gas old?
Use a gas can and fresh gas and a piece of gas line into the can. Try to get all old gas out of filter and carb. Smell the gas and does it small like gas or something else?

 

[Scott Danforth]

I would stop throwing parts at it and start diagnosing.

most of the time your old carb may only need to be gone thru. the "remanufactured" QuadraJet carbs you buy may actually be worse than your old carb.

Start with verifying spark
measure fuel pump pressure (should be 4-7 psi)
verify engine compression (new motor is 150 psi)

 

[tank1949]

83' mercruiser 350/260hp alpha one outdrive with rochester quadrajet carburetor. replaced mechanical fuel pump.engine started and was run for about 10 minutes. several days later engine would not start so replaced carburetor. boat still failed to start except briefly on starter fluid checked fuel flow up to carburetor and is good.changed fuel filter and checked fuel and seemed
clean and not phase seperated. engine still refuses to start except briefly. ideas? thanks in advance!

May have run out of gas?????? How long has it sat?

 

[capt.snappy1]

Start by verifying spark, use a spark tester to verify length and color

Is the gas old?
Use a gas can and fresh gas and a piece of gas line into the can. Try to get all old gas out of filter and carb. Smell the gas and does it small like gas or something else?

gas is good.no foul smell of phase separation.treated and stabilized from last season. get engine started with difficulty and still seemed starved for fuel above 2000rpm. when finally got above 3000rpm tach went crazy going back and forth? ignition issues? ideas appreciated? thanks!

 

[Scott Danforth]

bad connections and gunk in your carb.

 

[capt.snappy1]

bad connections and gunk in your carb.

newly rebuilt carb.what connections?

 

[alldodge]

gas is good.no foul smell of phase separation.treated and stabilized from last season. get engine started with difficulty and still seemed starved for fuel above 2000rpm. when finally got above 3000rpm tach went crazy going back and forth? ignition issues? ideas appreciated? thanks!

With tach acting up it may be going bad. Disconnect gray wire on negative side of coil which is going to the tach

 

[Scott Danforth]

newly rebuilt carb.what connections?

Grey wire at tach, or grounds at the buss behind the helm