May Day help

[Built For Speed]

1987 Mercury Black Max XR2 150 HP (Serial 0A969708)


Engine starts immediately and runs great. I replaced the water pump, fuel filter, primer bulb, and filled it with fresh gas mixed 50:1. After about 10 minutes at high throttle, the engine gradually loses power and dies. If I wait a minute or two, it restarts but will only run at a snail’s pace. At idle and lower speeds it seems fine. Looking for ideas on what to check next.

 

[racerone]

Test run with a portable tank and hose.

 

[Built For Speed]

Test run with a portable tank and hose.

Thank you good idea

 

[Chris1956]

Check spark immediately after it dies.

 

[Built For Speed]

Check spark immediately after it dies.

Will do thank u

 

[Dukedog]

pump tha "bulb" when it starts ta act stupid.. if that works then its bad.. next push tha key "in" (activates tha enrichner circuit) and hold for a few seconds when it acts up.. if that makes tha motor come back ta life ya have a bad fuel pump