The 1973 Mercruiser 140 engine that was swapped into my boat in fall 2014 runs, but it is difficult to start, after not running for a week.
I was told that the carb was rebuilt when the engine was installed in my boat. I don't know how complete the carb rebuild was, however. For example, I'm not sure if the carb fuel pump (called accelerator pump?) was rebuilt, too.
I can see that new fuel hoses were put on. I believe that the mechanic put in new spark plugs, and would guess a new fuel filter, too.
He reused my nearly-new spark plug wires and updated electronic ignition distributor body and cap.
The mechanic winterized the engine after the swap. The fuel tank was less than 1/4 full and Starbrite Star Tron Enzyme Fuel Treatment was put in the gas. In the spring, I put about 10 gallons of non-ethanol premium gasoline in the tank.
I have been following the recommended cold-start procedure (push in the shift release button, pump throttle lever once to set choke, pump another time to squirt fuel into the carb), and the starter cranks and cranks without firing.
I have found that I must pump the throttle lever 5 to 10 times and have the throttle at about 50% before the engine will fire while the starter cranks. Then it dies as soon as the starter is turned off.
After approximately 5 near-starts from pumping the throttle and cranking for 5-10 seconds, the boat will finally start.
After it finally starts, and still cold, it will only run smoothly at 1000 RPM or more.
At 700 RPM, it barely keeps running.
This weekend, while in the lake, I turned up the idle set screw so the in-gear idle speed is 1000 RPM, to keep it from nearly dying when maneuvering at slow speeds around the dock.
With this higher idle setting, the in-neutral idle speed is about 1200-1300 RPM.
After the engine warms up to 140-150F, and I put it into gear to go out into the lake, I must increase the throttle slowly or the engine dies. So, no fast takeoffs (forward or reverse) are possible.
What are the likely causes of these symptoms?
Poor fuel delivery? (bad carb accelerator pump? weak main fuel pump?)
Wrong carb mixture screw settings?
Eric