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502 mag mpi spontaneous stalling at extended idle times

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502 mag mpi spontaneous stalling at extended idle times

Old 08-29-2013, 02:33 PM
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I think the ICM is around $80 if I remember correctly. There are two, of coarse you need the MORE expensive one. I don't recall changing the coil. You'll have to pull the plug on the sea/fuel pump res. I bet it's full of gas, it should have 4-6 oz of gear lube.

I've run my '97 502 with the VST for 13 seasons in Texas. Well over 100* many many many times, she's never vapor locked once. Good Luck.
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Old 08-30-2013, 07:22 PM
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Well after removing the mechanical pump I found the housing it was in was full of gas. Hopefully that means it is bad and replacing it will fix my issue. The only bad thing is I can't have a new one til Tuesday after Labor Day, bummer. Thanks for all the advice will update the situation after I install the new parts and get to try it out. Keep up the great help all!!!
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Old 08-31-2013, 10:47 AM
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Here's a pic of the wear on my pump's foot.

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Old 10-06-2013, 01:46 PM
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Well it's been a while, but cap, rotor, fuel filter, and new mechanical pump, my boat is fixed. Thanks a bunch every one for taking time to help fellow boaters.
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Old 10-08-2013, 10:19 PM
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I just bought the same boat last year and dropped in my 502's same problem, also I noticed the coolant temps crept high when I was running it above 40 MPH, for grinns I dropped in a a pair of 143* thermostats and the problem mostly went away (it happened once since, on one engine). Had the problem stayed I was planning on returning the bypass fuel to the tank or installing remote fuel pumps returning the bypass to the tank. Tons of post on the issue, theirs no question it's Vapor Lock.
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Old 10-09-2013, 08:18 AM
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if the 502 is an mpi the 143 thermostat will keep the engine to cool and it will stay in cold start rich mode,needs the 160 for correct enrichment
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Old 01-30-2014, 12:23 AM
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Never had a problem with temps but last time for the season that I had the boat out after the fuel fix, one time a warning horn went off have no idea what it was. It came on as soon as I was getting on plane, I immediately went to idle raised engine hatch and visually looked things over and saw nothing wrong. Continued down lake at speed and never had any problems but didn't have to go to far( 6 miles at most) . Took it to get winterized and they had to replace sea pump, and showed me the old one there was nothing left other than a rubber hub and bushing. Is there a water pressure warning horn even though I don't have a water pressure gauge? I'm used to running older bass boats (2 strokes) where there is only a oil warning horn. My owners manual doesn't have any explanation of warning horns for my boat. 1997 271 formula fastec 502 mpi
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