CONTINUOUSWAVE

I recently purchased a 315 Conquest with [twin production-year 2012 Mercury VERADO FOURSTROKE 250-HP engines] on March 29, 2018. The engines had just had their 200-hour service by Marine Max in Naples, Florida. I used the boat down there [two times] and up north in Boston [five times for] maybe eight hours.

Last trip out the port engine quit. It didn't just stop but slowly throttled down and the stopped. I could restart it, but it would continue to do the same thing.

In a few cases it would idle for a little bit ,but; then just stop. I am still waiting to get it in the shop. Don't want to wait.

I am looking for suggestions on [how to diagnose and repair the problem described above by myself].

Check the fuel floats in both engines. There was/is a Mercury Marine recall for the float replacement. I suggest a Google and/or U Tube search for "Verado Fuel Float Replacement". That may help you to decide if that is your problem.

Buy the Mercury shop manual,

Buy the Mercury digital test system.