Carbs or Compression???

[snowstud98@hotmail.com]

Hey Guys I have a 1975 Merc 50 HP that sat idle for 20 years, I cleaned the carbs,rebuilt the fuel pump and acourse a new water pump..started right up..this is the problem I idles great,but when i put it under load it stalls out.If I floor it I goes about 10MPH hr then bogs down to 5 or so...it does really miss though.. Heres my questions??<br />1. I did a compression test on a warm engine.I cranked the starter for about 2 seconds and all 4 cylinders were in the 90's.. I did it a second time for 4 seconds and it was in the 120's..which one is correct???<br />2. I see a idle adjustment on the carbs but is there a high speed adjustment?? thanks Erik

 

[bootle]

Re: Carbs or Compression???

The compression numbers in your case seems to be fine, look for variances between the cylinders.<br />Recheck the fuel pump diaphrams and check-valves, also make sure that the fuel lines are air tight from the tank all the way to the carbs.<br />Make sure that the fuel tank vent is operating correctly.

 

[timmathis]

Re: Carbs or Compression???

Sounds fuel related. Darth told you right. Check what he said. You have good spark right?

 

[tmcalavy]

Re: Carbs or Compression???

Had the same prob on my old 73 Merc 500 after doing a carb rebuild...geez what a chore, just getting to the carbs. Sounds like your ignition/carb synchronization is off. I paid the Merc guy at our local marina/boat place $50 to do a link & Synch...ran like a champ till I sold the rig about 2 years later. But check what the other posts suggest, you never know.