1969 4 HP Merc choke

[FlyGuy]

OK--I have a 1969 4 HP Merc. Also, I am not the most mechanically inclined but I am learning. This spring she would not start--I must have failed to run her out or something. Since then I have rebuilt the fuel pump, float assembly and the carb. <br /><br />Now, the things runs great WHEN IT IS CHOKED! (by that I mean the choke plate is in the "up" position--the vented part is in front of the carb not the solid part). Otherwise it dies out. What is wrong? I assume it is a simple idle screw adjustment or something....But I have tried it al the way in to all the way out and she'll ony start and run with the choke "up" or "on".<br /><br />BTW--what does the choke do?

 

[JB]

Re: 1969 4 HP Merc choke

Howdy, Flyguy. The choke restricts air intake to make the fuel/air mixture richer. It is usually needed to get the engine started and sometimes partial choke is used to keep it running while warming up. It should not be required to keep the engine running after it is warm.<br /><br />Your engine is behaving as though it is not getting enough fuel from the usual sources: the low- and high speed jets in the carb. In some carbs there is also an intermediate speed jet. They are probably gummed up and require cleaning. Get every tiny passage clean. Use small wire and air pressure if required.<br /><br />When you reassemble the carb, screw the adjustable jet needles in to the seat, then out 1 to 1.5 turns.<br /><br />Good luck and let us know what happens.<br /><br />Red sky at night. . .<br />JB

 

[FlyGuy]

Re: 1969 4 HP Merc choke

When this all started I suspected a fuel supply problem so that is why I reebuilt the pump and float assembly (after checking lines,tank, bulb...). I just got done cleaning and rebuildng the carb..had the jets out and they are clean. I cleaned the carb body as well as the new needle valve for the float (the float is new too). Should I re-do it all? Could I have a bad gasket someplace? The only adjustment is on the idle screw--the jets are screwed in and then hidden behind screw plugs.<br /><br />The other BI*** about this motor is that the starter cord is mounted to the engine cover--I cannot start the motor w/o the cover on and I cannot get the cover off once its started--anyone have the trick for that?<br /><br />Back the choke (since it ran so nice that way)--if it restricts airflow then why does the vented portion of the plate get put in front of the carb when the choke is "on"? Seems to me it gets more air that way?<br /><br />Sorry guys...I'm learning thus all the pesky questions. It's to the point now that I HAVE to fix it myself--its become a mission! Please help! The manuals do nothing for troubleshooting this problem.

 

[JB]

Re: 1969 4 HP Merc choke

Hi, Flyguy. Hmmm. For whatever reason, your engine isn't getting enough fuel when not choked. Because I haven't had a Merc 4 carb apart in about 20 years and don't have Merc manuals I am not able to get you any deeper into why.<br /><br />Try pumping your primer bulb and see if that relieves the problem. I might be that the carb isn't getting enough fuel from the tank.<br /><br />BTW, is that '69 a single or twin cyl.? If it is a single, pop the carb off and inspect your reed valves.<br /><br />Standing by.<br />JB

 

[FlyGuy]

Re: 1969 4 HP Merc choke

OK--I'll look at the reed valves (its a single cyl.)--what am I looking for? What do I do if I find what I'm supposed to look for?<br /><br />BTW--way back when I first had problems I could keep her running by keeping pressure in the primer bulb--bbut the thrittle adjustment was useless. That is why I first figured the pump was shot.<br /><br />At present the throttle works fine and so does the pump--I dunno but I know I'm mad.

 

[Rex]

Re: 1969 4 HP Merc choke

TRY ANOTHER FUEL HOSE. THE O-RING IN THE ENDS<br />GET HARD AND LET IT GET AIR.<br />SOMEBOBY WELL LET YOU TRY THIERS AT NO COST.