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Mag 350 MPI Running Rough, No Power

D

DonNC

New member
Hi all. My 2004 Mag 350 MPI Merc is running very rough and I’m looking for any ideas to troubleshoot it. It’s been sitting for about a year and I just took it out for its first run. It’s got new plugs, wires, cap, rotor, oil and filter, water separator. . Before I took it out, I idled the motor in my driveway on muffs and it had good water flow but overheated (not sure of the temp but the alarm came on). I pulled the thermostat, tested it, and it opened at 160. I assumed the overheating was because it wasn’t getting enough flow so I took it out on the water to check that. I was on the water for about 15 minutes and it didn’t come up to normal temp (ran about 130 degrees), had very little power (12 knots at WOT) and I smelled fuel in the exhaust. The fuel is non-ethanol and less than a year old. Anything I can try or do I need to send it to the shop so they can put it on a computer? Thanks for any help!
 
Last time you changed water pump impeller? FW/SW? I assume only OEM parts and NGK plugs. Clean the 20 yr old flame arrestor.
 
I'm assuming Alpha drive?
Verify shift interuptor switch is operating normal or you will be stuck in base timing mode.
 
sab said:
Last time you changed water pump impeller? FW/SW? I assume only OEM parts and NGK plugs. Clean the 20 yr old flame arrestor.
Click to expand...
The impeller was done 3 years ago, with about 30 hours running since then. Both FW and SW, about 50/50. Yes, all OEM parts. I’ll clean the flame arrestor. Thanks.
 
Droid said:
I'm assuming Alpha drive?
Verify shift interuptor switch is operating normal or you will be stuck in base timing mode.
Click to expand...
Just checked and it turns out it’s actually a Bravo 3 drive so there’s no switch. 🤦‍♂️
Is there anything else I can check? I did clean the flame arrestor like sab suggested above but haven’t taken it out on the water yet to test it out. Thanks again.
 
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