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  1. C

    5.7 Vortec dist, trying to seal the cap/rotor due to constant corrosion. Merc 350 Mag MPI Horizon.

    Oil pan has quite a bit of clearance, and I run the pumps on manual override often. So far the oil pan is rust free.
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    5.7 Vortec dist, trying to seal the cap/rotor due to constant corrosion. Merc 350 Mag MPI Horizon.

    Even if the weather is mild, when we wash down the deck with saltwater it goes in the bilge. In September I went albacore fishing, we caught 400 lbs. of albacore in two days. Lots of deck wash water drained to the bilge, but I run the pumps often to keep the bilge as dry as is possible. If...
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    5.7 Vortec dist, trying to seal the cap/rotor due to constant corrosion. Merc 350 Mag MPI Horizon.

    I recently installed some weatherstrip at the engine cover. This appears to be helping, however there are always a 2-3 gallons of saltwater present in the bilge under the engine. I believe moisture through out the engine compartment seeps in under the cap. Engine uses the "crab cap". A paper...
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    5.7 Vortec dist, trying to seal the cap/rotor due to constant corrosion. Merc 350 Mag MPI Horizon.

    I have an older boat where the deck water drains into the bilge. Due to the high moisture in the engine area, and that it is in saltwater for months at a time, the distributor contacts corrode quickly. My current method to keep the engine running smoothly is to clean the contacts with a soft...
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    350 Mag MPI intermittent rough running.

    I tried swapping an automotive TPS, but the indexing tab was in a slightly different location than in the Merc. TPS. After reinstalling the original TPS, engine ran almost perfect. Chased blue fin tuna for much of Monday, trolled for hours, the engine went back to 600 rpm each time. I suspect...
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    350 Mag MPI intermittent rough running.

    I trolled all day for bluefin tuna, engine ran great at 600 rpm for hours at a time. But after cruising for even a few minutes it would not come down to idle/600 rpm. When it stays at the 800+ rpm, definitely is running rich. Will be replacing the TPS and the ECT temp sensor as soon as I have...
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    350 Mag MPI intermittent rough running.

    What is ECT?
  8. C

    350 Mag MPI intermittent rough running.

    Will work on the computer scanner Saturday. I had the injectors overhauled 600 hours ago, every time I checked the TPS numbers, they have been normal. Vacuum leak, I agree is a possibility. Looked for one before, could not find one. For emissions, does this have much? There is no cat converter.
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    350 Mag MPI intermittent rough running.

    I changed the MAP sensor and the engine runs much better, but the problem was not completely solved. I have never been able to troll between 600 and 1,000 rpm. Now I can run at 700 or 800. During a half hour sea trial the high idle issue did appear once, but it was not as dramatic as before...
  10. C

    350 Mag MPI intermittent rough running.

    Also I noticed that the engine appeared to be running very rich, when the problem occurs. Thinking that a temp sender may be faulty so perhaps I may replace the MAP sensor.
  11. C

    350 Mag MPI intermittent rough running.

    Okay, will check that. Also the fuel pressure reading was 44 psi at all times, so that is good.
  12. C

    350 Mag MPI intermittent rough running.

    So connect the meter to the two center wires on the DLC, and there should be a voltage signal of some sort?
  13. C

    350 Mag MPI intermittent rough running.

    Good progress today. No loose or chafed wires that I could find. However when I compressed one of the IAC hoses, the engine smoothed out and went to idle. I tested the connector and found with key on there was 13 volts to the IAC valve, so possibly a sticking valve. A year or two ago I...
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    350 Mag MPI intermittent rough running.

    350 Mag MPI Horizon, s#OM675521 I checked the fuel pressure a few months ago, was 46 psi or whatever the spec is, can check again. Will test the DLC connector with a meter, good idea, thanks.
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    350 Mag MPI intermittent rough running.

    That is the first thing I did, about a year ago. I also changed the linkage to make sure I was getting full pressure on the throttle body plate. Another clue: Yesterday I partially warmed up the engine, running rough. Then I restarted and the rpms went to the correct 600 and the motor was...
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    350 Mag MPI intermittent rough running.

    This engine is FWC, has 1900 hours, but I have rebuilt the heads and replaced the timing chain set. Recently it will often start out running rough, and the idle will shoot up to 1,300 rpm. If I shut the engine down and re-start, often the engine will run correctly again. However the problem...
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    350 Mag MPI question on 555 relay fuse blowing.

    Thought I would give an update on what caused the problems on my engine. Primarily the newish coil had some sharp edges on the aluminum portion of the bracket. This abraded the wiring harness that was just above it, eventually shorting the wire the was connected to the 20 amp fuse. Second the...
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    Alarm Going Off for Mercruiser 350 Mag MPI

    Impeller could be weak, causing low water pressure. The Merc Guardian system is reducing your RPMs to 2,500. Best to get a code reader.
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    350 Mag MPI question on 555 relay fuse blowing.

    Thanks for the recommendation. I have the old coil, there was nothing wrong with it. This weekend I will do some testing with my ammeter, and swap some parts. Will try to determine what is causing the circuit overload.
  20. C

    350 Mag MPI question on 555 relay fuse blowing.

    A year ago I pulled the IAC cable off while the engine was idling. An hour later a 20 amp fuse blew. This fuse powers the fuel injectors and coil. Twice since then the same fuse blew, and today it blew twice more while out in the ocean. It tends to blow just after increasing RPMs to cruise...
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