Mercruiser 350 MAG dies after long idle

[haniamr]

New to inboard engines so apologies for my lack of knowledge in advance. Here is my boat info:
- 2005 Amberjack 290 with twin v-drive Mercruiser 350 Mag horizon engines
- ~250 hours on each

Issue started after a 15-20 mins idle, my port engine turned off and wouldn’t start back. After moving throttle back and force to wot it sputters then starts after 10-15 mins, then runs fine and gets to cruising rpms easily.

Things i’ve checked/replaced so far:
- Spark plugs
- Distributor cap and rotor
- Fuel filter (just the cartridge not the round mesh disc on the bottom)
- Cleaned flame arrestors
- Reproduced the issue while docked at the marina and let it idle for ~30 mins, attached a fuel pressure tester and it reads 0 psi
- Opened the fuel filter housing and it’s empty
- Pressure tested the stbd engine (running fine) and it reads around 20-25 psi, and port reads around 15 psi when it runs fine

From reading it seems those pressure numbers are super low to what it should be (43), maybe the tester is broken or i did something wrong? Not sure but I just screwed it to the schrader valve so can’t see what I might have done wrong.

I’ve read a ton on the cool fuel module and the paint flaking problems, but I don’t think this is my problem since I’m getting no fuel at all. What should I look at next?

I read that the cf module might get hot with low water pressure (also if the passages are blocked) so it causes a vapor lock/pumping issue? I thought I’d pull it off and clean the passages but heard I might end up breaking the water hose connections so have to be prepared to replace those. Is that the right direction to pursue?

Thanks!

 

[Steve618]

Check the idle control valve, sounds like the same problem I had, replaced both of them on mine. Buy quicksilver/ mercury parts, don’t go cheap

 

[haniamr]

Thanks it turned out that the raw water passage in the cool fuel module was completely blocked with salt, so I cleaned it and it ran fine since then.