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Twin 74 Mercs Low Rpmbs raw fuel at exhaust

A

atx

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"Have a 33' Wellcraft with

"Have a 33' Wellcraft with twin 7.4's, V Drive. All maintenance is up to date. Boat was only getting 3200 rpm's on both engines at full throttle. I changed the spark plugs over the weekend and the rpm's went to 3900 on the port side engine and 4200 on the starboard side. Next I will be changing the sparkplug wires and caps and rotors.

Also having issues with raw fuel coming out of the exhaust. I have a feeling this will be the injectors. Anyone have any ideas of where to start? Thanks ahead of time."
 
"Do the wire, cap and rotor ch

"Do the wire, cap and rotor change and see if that helps. A cylinder(s) that is misfiring can pass unburned fuel, so eliminate lack of ignition as a cause before you look any further."
 
"Your plugs were likely badly

"Your plugs were likely badly fouled due to running rich, for new ones to have made such a difference. Are your flame arrestors clean?

Your injectors may be dirty. EFI boats have a nasty habit of doing this due to long periods of inactivity.

I would try a dosing or two of injector cleaner in your gas, and see if that makes it any better. If not, check your injector rail pressures, and lastly you may need to replace your injectors, or take them to someone who can clean them properly.

If it ran fine previously, there is nothing wrong with your ECM programming, unless you have changed something in your intake or exhaust systems, or your air intakes are restricted.

Rod"
 
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