1973 Merc 500 dying

[mbnjagn]

Hello,

I have a freshly rebuilt 1973 Merc 500 that I am having a small issue with. The engine will cold start fine and run all the way up to 5000 rpm with no issues and then idle. The problem comes after running the engine awhile when I slow down to idle and keep idling for a while like picking up a downed skier or tuber then go to slam it down to pull up the skiier it dies out and is very tough to start. When I do get it started I have to do some fast idling then slow down and hit the gas and it works 1/2 of the time. I have noticed that the primer bulb does get a little soft at idle. The fuel pump and carbs have all been rebuilt with the engine. Could there be an air leak in the line close to the fuel pump? There is a splice there with a couple of clamps and I have noticed some fuel/oil residue on the side of the engine block by the pump. If it was the fuel pump does it make sense that it works fine above 1500 rpm?

 

[ricksrster]

Re: 1973 Merc 500 dying

Looks like a fuel leak. you might want to replace the fuel lines.

 

[mbnjagn]

Re: 1973 Merc 500 dying

Thanks for the reply.

Would that explain why it works at the higher RPM's?

 

[pman7]

Re: 1973 Merc 500 dying

Another idea you might want to try is backing out the high speed jet a quarter turn on both carbs. If this doesn't help try another quarter turn.

I have a 71 Merc500 that was owned by a friend of mine about 2 years ago and he was having a similar problem as you described. I don't think the motor was always dying but either dying or fallin on it's face so to speak. Someone on this board recommended backing out the high speed jets and the first quarter turn corrected the problem.

 

[mbnjagn]

Re: 1973 Merc 500 dying

Thanks.

I had already done this. It would seem to help for a while but then when you test the engine it would act up again.