cobra omc missing when warm. why?

runs fine for half an hour then only on full throttle starts missing as if only firing on four or five cylinders pull back to half power and runs fine.

 

Check out fuel filters and tank breather. We gotta start somwhere and thats where I would go. It sounds like not enough fuel to run the cylinders at that RPM so we got to think why.

 

Thankyou for your response to my problem and in the morning I have a guy coming down to start looking at her so I will ask him to start there.
But why always after half an hour does it happen ? I went out today and it happened again after the same amount of time, if it was fuel would it not be a constant problem at max rpm ?

 

Fuel filters can be partialy restrictive, Fuel tank breathers also therefore the problem may occure after time. A quick way to check the tank breather would be to temporarily remove the filler cap. Do you hear a rush of air into the tank when you do remove the filler cap? Is it fuel injection or carb?

 

There was a similar problem on some GM cars. The tank vent line to the charcoal cannister (emissions) would kink, and as the gas drained out of the tank creating a vacuum, outside pressure would push the bottom of the tank up - lifting the fuel pickup out of the fuel and causing the car to stall with a quarter tank of gas still showing. Quick fix was to open the gas cap and then continue driving.