Starts but won't run 1971 50hp Mercury 500

[Wolfie819]

Compression 125all cylinders great spark seams to be getting fuel.......starts but stalls after 5_10 seconds
I cleaned the carbs they look good the timing seems to be set correctly I tried to run it on an IV bottle direct to carbs no difference before or after fuel pump does this engine require a certain amount of pressure to run or is there something else I should be looking at can anyone help...... Thanks

 

[SparkieBoat]

if you got the proper amount of fuel, compression and a properly timed spark it should go boom. one of these 3 is missing. check your spark on all 4 cylinders. (I think that one is a 4 cylinder, I got a 74 that is just like it probably.

 

[Wolfie819]

The spark is awesome all four cylinders

 

[GA_Boater]

Do a compression test for starters. Worn rings or scored cylinder walls can cause all kinds of funky running problems.

And welcome aboard, Wolfie.

 

[Wolfie819]

Again compression on all 4 cylinders is about 125 that's why I'm asking about fuel pressure everything seams good it tries to run but then it dies as if it is out of fuel yet when I check the plugs they are wet with fuel and oil

 

[GA_Boater]

Missed the compression #s in the 1st post. Do you have an inductive timing light? If you do, put it on one of the plug wires and start it. See if it keeps making spark when it dies.

Where did you set the Idle Adjustment screw?

 

[SparkieBoat]

sounds like you may have a fuel pressure problem try pumping the bulb constantly and see if that keeps it running, if it does this would indicate either a bad fuel pump or a fuel line connection or crack in the fuel line hose sucking air, or possibly a clogged pick up tube or fuel tank vent

 

[Wolfie819]

Can anyone tell me what voltage I should have at the trigger box from the ignition switch

 

[SparkieBoat]

click on the CDI link in my sig below. a free troubleshooting guide. gives you test for your electronics. You will need a DVA adapter. there is a link for that too.

 

[Wolfie819]

Thanks at least I can now test the trigger box however I don't think it is the problem as I have good spark on all plugs even as the engine dies I still think it is a fuel issue even though it should be getting the fuel I don't think it is

 

[SparkieBoat]

well if it is a fuel issue then you either have a bad pump, bad fuel line/connection/clogged pickup tube in tank or carbs that need cleaning adjusting..that should about cover your fuel issues.

 

[Wolfie819]

No Title

Well I've tried everything else so I opened the motor to get to the reeds and this is what I found a couple of the reeds are slightly lifted as you can see in the photo is this enough to shut down the engine???