Re: mid 70 mercury 50 thunderbolt fuel issue
There are several things that can cause the hard starting when the motor is warmed up. The first item is that you will need a manual for the motor if you do not have one already. The do a step by step testing of the motor starting with a compression test, then testing for good spark at the plugs. This will tell if there is trouble with the electrical of the motor when it is warm. after that check all the fuel system and all the hoses on the motor for cracks or where air leakage could happen. The if all is good then go thru the fuel pump and carb to make sure all is good there. It could be that the crankshaft seals or gaskets on the block leak after the motor gets warmed up also. When working on motors that are over 25 years old, time will take its toll even if all the maintance has been done as it should have been. Using a piece of clear hose from the fuel pump to the carb will let you see if there is any air leaks from the furl tank to the carb. Any air bubbles in the hose is a sign of air leak in the fuel system. Always replace the clear hose with gas hose, as the clear hose will not last as such. JMO
Oldman570
