Unburned fuel and alarm

kbgolf1

I have unburned fuel coming out of my port side engine.  Engine starts and will run for about 10 mins (give or take).  I have a loss of power (at 3800 RPM's I usually hit about 20 knots and I am only hitting 16 knots now).  Mechanic has been here a couple of times and replaced the spark plugs, distributor cap and rotor.  Anybody have this issue in the past?  Could it be cam/crank shaft position censors and/or a timing issue?

LaRea

What year and model?  

JoeStang

Is the engine getting up to temp? Mine did something similar and the thermostat was stuck open (small pebbles in the spring) and it was running way rich because it was staying too cold and running open loop.

kbgolf1

2003 Fiesta Vee 342

kbgolf1

Temp is normal and running about the same on both engines.

kbgolf1

Engines are Mercruiser 350 5.7L

JoeStang

What temp are they getting up to and is it an analog or digital reading?

JoeStang

Also search cool fuel issues

Wildboating

KBGOLF1,  What did the mechanic say about the alarm?  Did he scan the motor?