78-115 shuts off at WOT

[laserfish]

Starts and idles better than any engine I have had. Idled out of the marina and gave it the gas. Ran up to 44 mph and sounded great. After about 15 seconds it was as if I turned off the key. Started right back up but as soon as I gave it throttle it died again (multiple times). Idled back to marina. Fuel flows freely. New plugs, rectifier, fuel line, fuel pump, carbs CLEAN.
Second time out same thing...15 or so seconds at WOT it shuts off. This time it will not restart. Fortunately have a good trolling motor to get me back. HELP PLEASE. What to check.

 

[racerone]

Step #1 is a spark check.----Does spark jump a gap of 3/8" or better on all leads , yes or no ?

 

[oldboat1]

overheating? Impeller replaced?

 

[laserfish]

New impeller, water pressure 15 psi or more on gauge, check spark tonight.
Keep the ideas coming and thanks.

 

[oldboat1]

What is the operating temp, measured on top of the heads? If you can hold the heel of your hand on top for a few seconds, temp should be OK. An infrared heat gauge would be a good addition to your tool box (160F is overheating).

 

[laserfish]

Boat is a couple of hours away and I am heading out there this weekend. If there is no/weak spark, what to check, and how to check next. Won't start now and I know it has fuel and air. No stores out that way so I want to go prepared. With the water pressure, and new impeller I am confident overheating is not an issue but will check when finally started.
Thanks

 

[laserfish]

Racerone, finally got to look at this and there is zero spark. Where to troubleshoot from here.