1970's chrylser - 70 hp high speed miss

[jeep8589]

I have a 70hp 1970's model chrysler outboard and it seems to starve for fuel at wide open throttle. When you first open it up it runs fine, and after 10 seconds begins to miss. You can actually see the fuel start to run out in the sight glass on the fuel pump. I have rebuilt the fuel pump and there is new fuel lines running from the tank. Back the throttle off just a touch it it quits missing. I have johnson quick disconnects on the fuel tanks and have the breather open. The fuel line from the tank is 5/16". Suggestions on the reason for the fuel starvation. Are my fuel lines adequate size or do the need a different disconnect to provide more fuel. The vacuum lines are also new to the fuel pump.

 

[eurolarva]

Re: 1970's chrylser - 70 hp high speed miss

Was this a pre existing condition before you replaced the fuel lines and the fuel pump? Try seeing if it improves by unscrewing the gas can cover. Another post here today mentioned he had a defective oring on his quick disconnect which created air being sucked into the gas giving him problems at wot. The float on one of your carbs may not be set correctly, one of the fuel valves in your fuel pump could be bad or you could have an air leak. Poor compression could also be the problem. Also the screen in your gas can could be partially plugged reducing the amount of gas that can flow.<br /><br />I would pursue the air leak first then look at the carb. If your fuel valves are bad you should order them and gaskets in advance. Two are press fit and a bear to get out without breaking. If you decide to order them I can provide mercury part numbers for these parts along with the correct gaskets.<br /><br />Also can you pump the bulb so it gets real firm without leaking gas on your carbs? What do your plug contacts look like?