2016 Merc 8.2 I/O
Since new in the first few years - power steering seal let go, engine wire harness short, harmonic balancer separated, new starter, always seem to need excessive cranking to start for a modern EFI engine, last week, bad oil leak from the oil pressure sending switch. My new issue since getting the boat back from service is after I ran for a while, I shut down and drifted for a while then started the engine and it just idled down and died. it 2 or 3 more tries before it stayed running. This happened the 2 times I ran for a while and shut down. Engine ran fine after it stayed running. Any idea what this issue could be before it goes back to certified Merc shop again ???
Thank You !!

Maybe fuel vapor lock.

Thanks for the reply.
Never did this stalling/ stalling thing before even in upper 90's temps

The symptoms do sound like a partial vapor lock. Maybe try opening eng hatch next time while drifting and see if that helps. No idea why its starting now. Maybe you ran it harder and let it idle for a shorter time before shutting down? Engine temps at the normal level before shutting down?

Idle air control valve?

Temps are fine, new sea water pump impeller just installed. Boat was driven in no wake zone before shut down for a while. No different than my regular outings...

thanks for the replies

my buddies 502 FI motors would often vapor lock early in the season depending on if he didn’t wait and get a good summmer blend fuel in it. Evidently the marina ran different blends in winter/summer so he was careful to always fill up once summer blend showed. Take it all with a grain of salt but just offering it up….

Agree with group, to verify the issue
Next time it does it find the cap and schrader valve (items 23 and 22). Remove cap and with a rag and small screw driver press in on the schrader valve with rag around valve. You want to see if gas comes out or air and gas. If there is air then it's vapor lock and doing this purge it should fire right up after a couple more prime cycles with key ON/OFF

https://www.mercruiserparts.com/bam/...1945/14733/150

Will hopefully go out on boat tomorrow and try the bleeder and check for air.
thanks for the suggestion

Ended up being idle air control valve.
I will get the boat in am and hopefully it will run well. Thanks again for all the responses.