1972 Mercury 402 not getting fuel into carburetor

[RandyJ]

Hoping I'm just overlooking something simple and stupid. Fuel is getting into bowl but none in carb. When I spray starting fluid into carb it starts right up. This old motor was running as good as new. I let it set on my pontoon out in the lake for a couple of months and when I tried to start it would not run. I pulled it out of the water and found lots of water in the gas. After cleaning the whole fuel system it ran ok on trailer. When I put it in the water it would not start. Again I found more water in the tank. Now, i pulled it out again and cleaned the carburetor and whole fuel system as I've done many times before. It simply is not sucking fuel into the carburetor from the bowl. Any suggestions as to why?

 

[wolfee]

I have a similar problem. My 25hp Merc will not start (pull start) no matter how many times I pull. One shot of starter fluid (yes I know it's not good to use) and it starts in one pull. I took it to the lake yesterday and same deal, once it started it ran and idled over 3 hours perfectly. Once it's off, won't start w/o starter fluid. I actually did the SeaFoam carb/engine cleaner treatment and I thought it fixed the problem but sure enough, won't start w/o starter fluid. The only thing I can think is that it's either the float or the needle, but they're both pretty much new and I set the float according to the merc manual. Not sure what to do at this point.

 

[RandyJ]

I have a similar problem. My 25hp Merc will not start (pull start) no matter how many times I pull. One shot of starter fluid (yes I know it's not good to use) and it starts in one pull. I took it to the lake yesterday and same deal, once it started it ran and idled over 3 hours perfectly. Once it's off, won't start w/o starter fluid. I actually did the SeaFoam carb/engine cleaner treatment and I thought it fixed the problem but sure enough, won't start w/o starter fluid. The only thing I can think is that it's either the float or the needle, but they're both pretty much new and I set the float according to the merc manual. Not sure what to do at this point.

I have a good idea what my problem could be. I posted the question to see if anybody else has the same idea or can offer a way to confirm the problem. The fuel system on these old outboards depends on vacuum to pull the fuel into the crankcase through the carburetor. First thing to check is the base gasket of the carburetor and any other possible area where vacuum could leak. The only other things I can think of other than worn rings is leaking reed valves or crankshaft seals. I'm looking for an easy/reliable way to diagnose which it may be. I've known of cases where the crankcase had a leak where the halves meet. All the fuel pump does is deliver fuel to the bowl of the carburetor. The vacuum pressure is what brings it into the engine. When you squeeze the primer bulb you are just imitating the function of the fuel pump which operates off the pulsing change of pressure/vacuum in the crankcase.... on lawnmowers and many other motors this air pressure is conducted via a "pulse line" or tube.

 

[RandyJ]

Hope Chinewalker will read my OP and give me some tips.... I've been reading his posts for at least 17 years....

 

[Chinewalker]

You've pulled the carb off to clean it? All jets are clean? Fuel tank has been pumped dry and fresh fuel mix added? Is the choke operating properly? Closing fully?

 

[RandyJ]

You've pulled the carb off to clean it? All jets are clean? Fuel tank has been pumped dry and fresh fuel mix added? Is the choke operating properly? Closing fully?

Yep. Everything seems to be working like it should. Gas pumps into bowl on the WMK carburetor but none is being sucked into the carb. Base gasket is good. I shot carb cleaner through all the holes and cleaned all the jets. The weird thing is that when I pulled it off the nozzle had backed out and was in the bottom but it had been running pretty good before I moored it. It cranks right up with a shot of ether but will not stay running. Got to be a major vacuum leak somewhere.

 

[cutty83]

Hi did you ever find out what the problem was? im having the same problem with same symptoms. lemme know

 

[RandyJ]

Sorry for not following up on this post. I finally gave up on that motor. However, I did buy a cranshaft seal to see if that would fix the problem. My guess is that being 46 years old the rubber in the seals could be cracked and not holding vacuum or pressure to move the fuel into the engine.