"Blubbering" 1976 Merc 500 50hp.

[Codeman96]

Ok I hope I can explain this. I have the above mentioned 76 Merc 500 4cyl with a jet pump on it. Back earlier in the year I noticed that at full throttle it would occasionally blubber (don't know a better way to describe it) through the exhaust. It didn't really feel like a miss, just like it was breaking up a little. Well it seems to be getting worse. Its more often and now it has done it enough that I have actually felt some power loss when it does it. I really only seems to do it when the motor is warm. The carbs were rebuilt about this time last year and it has had less than 20 hours on it this summer. Does this sound like it could be carb related? Ignition related? Is it running too hot? That being said it is peeing out of tale tale no problem.

If you guys need anymore info please ask, I'm kind of feeling around in the dark here. I know I am capable of fixing whatever it is, I'm just not sure how to trouble shoot it. I have a factory shop manual for it as well.

 

[Laddies]

Re: "Blubbering" 1976 Merc 500 50hp.

It sounds like a rich condition caused by a leaking inlet or incorrect float level or just plain ethanol poisoning.

 

[Codeman96]

Re: "Blubbering" 1976 Merc 500 50hp.

Well that is where I was headed was a fuel problem. After thinking about it a little more, it only does it when you get into the carbs past half throttle. What should I be looking for as far as the ethanol poisoning?

 

[Laddies]

Re: "Blubbering" 1976 Merc 500 50hp.

Ethanol, causes deterioration in fuel system parts made of neopreme type products. I have seen inlet needle tips swell up and also turn tpo jelly so it can eat your fuel line of fuel pump diaphram. The products being built as replacement parts are suppost to work with E10 but many stations are pumping fuel that is beyond 10% so you can still have problems with them.

 

[sschefer]

Re: "Blubbering" 1976 Merc 500 50hp.

Ahmen Laddies.

 

[Codeman96]

Re: "Blubbering" 1976 Merc 500 50hp.

Thanks Laddies, my carbs are coming apart tonight. I rebuilt them with new kits and fuel lines last fall but I don't remember changing the needles. Hmmmm.

 

[Laddies]

Re: "Blubbering" 1976 Merc 500 50hp.

Be sure to look the floats over and reset the levels

 

[Codeman96]

Re: "Blubbering" 1976 Merc 500 50hp.

Well I have them apart nothing really surprising. I did find a chunk of something in the bottom carb bowl and the needle on the bottom carb have a bit of a ring "worn" in it. I'm thinking new needles all around and clean them up again and set the floats and see what happens. I'm going to drain the tank too and check for water.

 

[Codeman96]

Re: "Blubbering" 1976 Merc 500 50hp.

Well after cleaning the carbs and completely draining the fuel system all seems to be well. I wasn't able to get parts so I juts put it back together. Ran like a champ this evening. Thanks for the help.