TOPIC: 89 Mariner Classic "45" in-line 4 Fire.

Was cruising all summer on my daughters' Classic 1970 Harris Flote Bote pontoon powered by a 89 Mariner 45hp.
After doing some high speed running we slowed down to cruising speed. when the motor just stopped. The fuel tank was near emptty. So we assumed it was time to change tanks (6gal). No Go. Hasn't fired up since it quit. No Spark. Any ideas out there?
It was running great since Memorial day.

Switch box was replaced about 8 years ago. But it was only firing on 3 cylinders when that went bad.