Mercruiser Engine cutting off out of nowhere ( great to know stuff)

[@BSwift-o2s]

Thank you very much for this suggestion! My port side cuts off for a second under way, along with the gauges so I will check this and also replacing start/ignition switch (370DA Inboards).

[@brianyechout1058]

I have something similar going on. It only happens when I’m above 3,700rpm, the motor goes off then back on like flicking a light switch. I’ve been going crazy as this thing has run flawlessly for the 10 years I’ve owned it. Thanks for giving me something new to check.

[@Cruisingthesouth]

Man, I just had one of those of something driving me crazy, I had the same exact thing that you are describing, only or high RPM the freaking engine flicking like a light switch on and off and I originally thought was my fuel pump so I went and replaced the fuel pump but guess what the problem did not go away just slightly differed, so guess what? I chased my tail for two weeks looking at things Thinking of internal intrusion or something, I couldn’t really figure out what was going on, turned out that the brand new fuel pump that I bought was already bad, brand new fuel pump defective, after chasing my tail for two weeks I put in a new new fuel pump and the problem simply disappeared. Go figure.

[@jimcatanzaro7808]

Buy the manual book for it u need to get rid of the stator first off and replace the seals for the water pump in the front of the motor

[@gcalda62]

Mine dies after it’s warm, usually on the way out, just stops. Replaced ignition coil, still happens, only when warm, usually starts right up again, but only runs a few minutes, I’m thinking vapor lock? Online filter and water/fuel filter replaced… still no go, electrical or fuel?? It’s a 4.3 GMC OMC Four winns 1988 with 137 original hours

[@papicarta6387]

Did you ever find out the problem? Mine is now doing the same thing

[@shanetyler9391]

Yeah mine will start and run at low idle when cold. then after running on the water for awhile when put into neutral it will die and not restart.i believe its a IACV idle air control valve.

[@izikrahmon8521]

My Baja 454 is having the exact same issue. Did you ever find out if it was actually the IAC?

[@direstrait5418]

Hi, why do you have a cracked cylinder head? I have same engjnes.

[@Cruisingthesouth]

Hello my friend! What caused my cylinder intrusion was rust from the inside out. The cooling channel that passes by the exhaust port developed a pinhole, because my engines was raw water cooled before, and that won the battle. Now I have it fresh water cooled

[@hakansundberg1954]

I had the same problem but it was wrong with my killer switch

[@Cruisingthesouth]

😮 that can be tricky right! My safety switch is by my transmission so is a little more reliable than thous that hide behind the throttle handle

[@timothyhelf6144]

Had the same problem on 2 boats now, original fuse ir fuse block, very anoying

[@Cruisingthesouth]

I had a feeling that this happens a lot! You right sooo anoying it can be tricky to find the problem. My neighbor would’ve saved a lot of money if he had a 12v tester.. after replacing starter and alternator and battery figured it out that the alternator wire that charges the battery wasn’t connected! 😄

[@timothyhelf6144]

Yup, I bought one when we bought our first boat and made the difference between self sufficient, and paying people.

[@24rp84]

@@Cruisingthesouth hey

[@codyjames8329]

Took it in salt water for the first time- came home and flushed it dies about 10 minutes in. Open the motor compartment and it’s smoking. No clue water was on it