1978 mercury 140hp cranks but doesn't start

[sundayboater]

I have a 1978 Mercury 140 hp 3.0 liter inboard/outboard engine. I didn't run the boat at all last year. I did put stabil in and fogged the carb when I stored it for the winter though. I had the carb rebuilt this year. When I installed it, I also installed an inline gas/water filter seperator, and I removed all the old gas and put in fresh gas. When I tried to start it, it wasn't getting any gas, seems the fuel pump gave out. Replaced the fuel pump and she started right up, run nicely, had to set the idle, and she was doing well. Now a couple days later, I started it up, in ran rough for a minute, and shut down. I tried to restart it and can not. It cranks, gets gas, has spark, but does not start. There is no kill switch connected. When it cranks, it doesn't seem to crank extremely fast, just medium, so I tried with my jumper cables, connecting from the car to help boost it. It does somewhat, but doesn't start. All these steps have been done in the driveway with water connected. Also, when you move the throttle, it receives gas into the carb. I took off a spark plug wire, connected another plug and held it to the engine, cranked it, and there is spark (running the blower). If there is spark, is there a higher degree that there has to be, or if you have spark, then it's good? What should be the next step? New plugs? New battery? Why did it run nicely and now doesn't start? I think I've done some good steps, but am now stuck. Any ideas would be greatly appreciated.
Tom

 

[Chris1956]

Re: 1978 mercury 140hp cranks but doesn't start

Tom, You might repost this in the I/O section. Those guys are experts.... Did you clean and gap the points? Maybe the condernser is bad? Is the timing correct? Sometimes the mechanical advance in the distributor can rust and not move properly.

 

[sundayboater]

Re: 1978 mercury 140hp cranks but doesn't start

Tom, You might repost this in the I/O section. Those guys are experts.... Did you clean and gap the points? Maybe the condernser is bad? Is the timing correct? Sometimes the mechanical advance in the distributor can rust and not move properly.

Chris,
I cleaned the points, did not gap, i cleaned the contact pointson the cap of the distributer, i cleaned the spark plugs, and put in a new battery. Still cranks and doesn't start.
Tom

 

[Chris1956]

Re: 1978 mercury 140hp cranks but doesn't start

Well, point gap does affect timing. Incorrect point gap incorrect timing. Mechanical advance in distributor is working. A guess is that it stuck in the advance position. But it is just a guess. Dump some fuel into carb and see if she will fire.