1979 merc 40 running problem

[u2jeff]

hi guys,rite i have a 1979 merc 40 blueband single carb.i use this engine on a 15ft cjr.the engine out of the water starts and revs up fine,in neutral and in gear.the problem is when its in the water.in low revs it tends 2 die out,loses power,sometimes stalls,starts up imidiately after tho.3/4 and full revs no problem,will run all day.it pumps water fine no probs there.if u squeeze the fuel primer wen it dies it runs ok again 4 awhile.is this a fuel pump problem????or is it the float in the carb.......any ideas will be gratefully received..regards,jeff

 

[Laddies]

Re: 1979 merc 40 running problem

It sounds like you need a fuel pump kit, it's a easy job--Bob

 

[u2jeff]

Re: 1979 merc 40 running problem

thank u.il try that

 

[u2jeff]

Re: 1979 merc 40 running problem

hi,rite took fuel pump apart no problems there,diaprhagm in good order,took carb apart and cleaned and blew thru with airline.also replaced all fuel lines,put bak 2getha..the problem now is that it runs even worse.ive put a piece of clear fuel line on the pump so i can c wots happening,the line stays full of fuel,even wen running.the engine fires up and runs fine 4 about a minute,then it starts 2 die,slowly dropping onto one cylinder then stalling.it fires up first time tho and does the same again.ive got a little fuel dripping from the carb at the bottom now..is the float and needle knackered or is the whole carb.i also have 2 keep adjusting the idle screw,the spark plugs are ngk buhw.r these correct????please help,best regards,jeff

 

[Laddies]

Re: 1979 merc 40 running problem

Jeff it's not the dia. but the ck valves that usally cause problems a idle, but it sound know that you may as well do the carb also it should not be dripping fuel

 

[u2jeff]

Re: 1979 merc 40 running problem

hi,as ive said i put a clear fuel line on the pump 2 carb side,it stays full,even wen its dying.pumping the bulb does nothing wen its running rough.it runs fine 4 a few minutes wen started then starts 2 play up.ive blown down the inlet pipe on the carb and closed the float manually.it blocks off.do u know the float setting??????even wen it starts 2 play up petrol is still leaking from front of carb...is this flooding.

 

[tengals123]

Re: 1979 merc 40 running problem

how well did you clean the carb?? did you buy a rebuild kit?? change seat and float?<br />Originally you said it ran fine out of water, but died when in water?<br />now it runs fine for a few mins then dies? is that right?<br />still sounds to me like its a carb problem. cheers

 

[u2jeff]

Re: 1979 merc 40 running problem

hi,ive took carb off again and totally stripped it down,cleaned it with carb cleaner inside and out,now in soak in petrol bath.the needle seems 2 be sticking up in the seat.so il order a new one..i also took plugs out and they r black.hard dried on carbon.i only cleaned them wen i first used the engine.used 4 two trips.mixture 2 rich i think.checked compression on engine,no probs there.is there anyway i can decoke the internals of engine and not strip it down?????an additive or something maybe,available in britain.regards,jeff

 

[tengals123]

Re: 1979 merc 40 running problem

ok, your on the right track. Replace the ordered parts. Then decarb the engine. In australia i use power tune by quicksilver. People in the U.S us Seafoam. Do a serch here for seafoam and you'll get the idea. It works fairly well.

 

[destol cooper]

Re: 1979 merc 40 running problem

I don't know about decarb the engine, I've seen some bad things happen. Be sure to do just like the can says!<br /> Good luck

 

[u2jeff]

Re: 1979 merc 40 running problem

hi,rite carb is spottlesly clean.its now bak 2getha except top of float bowl.ive noticed the needle sticks 2 the top of the seat.u have to blow down it hard 2 free it.guess thats my problem......fingers crossed

 

[tengals123]

Re: 1979 merc 40 running problem

sounds about right.

 

[u2jeff]

Re: 1979 merc 40 running problem

hi,just like 2 say thank u 2 all those who replied 2 my problem,carb was stripped and cleaned thoroughly,replaced and it runs like a dream.many thanx again.regards jeff