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1978 70 hp Evinrude Starts but won't stay running

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duckhunterguy69

New member
I just got a tri-hull with the 70 horse on it. It starts pretty easy but won't stay running. It will only start at high throttle and I can keep it running by working choke back and forth. I tried running some sea foam through it but without it running it can't do much. I believe this is a fuel issue but don't know if it's fuel pump or carb or hoses or bulb? Pumping the bulb while running doesn't make a difference. Any help would be awesome, the fish are calling my name, thank you.
 
You've described a engine with fouled clogged, gummed carburetors.... clean and rebuild them. Make sure to manually clean the brass fixed high speed jets, located in the center bottom portion of the float chambers.
 
It looks like a vacuum line at the bottom of the stack of carbs. Is there some sort of air filter that should be on it with a spot to attach this vacuum line? Also, do I need to take the three carbs apart nd rebuild them or can I run sea foam through it to do the same thing. If I can start it for little bits at a time how long will the sea foam take to work? I really appreciate the info.
 
There should be a carburetor face plate assembly of which that rubber hose would attach between the bottom main bearing area and the bottom fitting of the face plate.

There is no short cuts in cleaning the carburetors. They must be removed, dismantled, cleaned, and rebuilt. Sea Foam is to get rid of carbon build up... it is not a carburetor cleaner.
 
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