Last night to go shoot some fish and at around 3800-3900rpms the motor was sparking out of the side around the oil cooler. It only did it under a load not in neutral. what could this be

Sounds like a skinned spark plug wire to me. Check the rubber bushing that the wire goes through to shield it from the plastic front cowling . Sometimes they slip out and skin the wire

Yep, plug wire arching on the metal shroud around the head.

common problem..

get new wires and wrap the shit out of them with electrical tape or slip some poly flow over them

Did you ever adjust your valves? I'm wondering if this is the cause of your pop you previoulsy posted and vibrations. If it misfired and then not getting a fluid current to spark that cylinder...

I never adjusted them yet

With a spark plug missing by grounding out, it coulda missed a few revolutions, the unburnt fuel got into the exhaust & backfired.

I'd check the spark plug wires and boot for any signs of chaffing. However with all the rain we have been having lately I have heard this complaint alot, and could also be a probelm with the coil (when it gets wet). Briggs changed their coils about a year ago to a fully sealed one which doesnt seem to have as many problems when they get wet.

check your connection.. could be loose like everyone is say'n. happen to me!