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Thread: Confused Engine Probs

  1. #1

    Confused Engine Probs

    99 Tige 21V Merc 350 Serial L305997

    Had a strange feeling power was progressively getting worse. Boat fell on its face while pulling a tube out of the water (after being in the river 6 hrs). Didnt die but had no power, rolled up the tube and headed for the dock. I was able to get up on plane and cruise 35mph back to the dock - its didnt get their fast but did get there. Loading on the trailer - had no power to push itself up there...had to winch.

    Came home and changed rotor, plugs, wires, tested coil, changed sensor under rotor, checked fuel pressure. I have a spark to every plug - said my firing indicator pen. oh also - I checked to see if any codes were in the ECM...nada 12 -12- 12- 12...

    Today, went and tested my work - seemed to be running good but didn't feel quite right- it wasn't purring. Fuel pressure gauge still on and holding a solid 42ish during testing. It never fell on its face but would not go over about 4000 rpms. I have an ACME 911 prop so thats not holding me back.

    I have another new coil so I was thinking about trying it. I guess I should do a compression test tomorrow to rule that out. Anything I'm missing? Can the injectors go bad (i know they can, is it common)? I am defeated today as I had two flat tires on my way back from the test.

    I'm not going to worry about it today; I have a date with vodka.

    Thoughts?
    Last edited by rski1; 08-09-2019 at 10:30 PM.

  2. #2
    Join Date
    Aug 2010
    Location
    Long Beach, CA
    Age
    44
    Posts
    1,108
    Boat
    2015 Z3, 1999 2100i
    Fuel pressure is way too high, should be 32 psi +-2. If the 42psi you posted was not a misprint, read on about fuel pressure, then the next section deals with non firing injectors. Most likely a clogged regulator which is mounted on the fuel pump cooler tube and has a brass fitting and washer assembly. REPLACE THEM ALL when you take off the regulator, 99% of the brass fittings break off into the regulator when you try to remove them and its not worth the hassle. $35 IIRC for the part. go to perfprotech.com and look up your serial to get the diagram and order parts from that. Fuel pump is located on the engine port motor mount which would be boat starboard. Very stupid design. You'll have to remove the water hoses and fuel line from the fuel filter and the high pressure line going to the fuel rail before you attempt to remove the unit.

    Injectors are also a likely cause of your condition and can easily be tested by running the engine and disconnecting each individual injector harness and reconnecting. Note a dip or rise in RPM when you do. Do not replace just that injector, replace them all. If 1 failed why? Oh yeah, ethanol. Means the rest are shortly behind and the new injectors are ethanol compatible.

    To remove the injector harness, pinch the two widest parts of the injector harness connection together and the holding clip will release. One side of the harness with have a small stainless retaining wire which wraps on three sides of the harness to injector connection. When you pinch the harness stainless retainer, the retaining clip releases. Wiggle and pull the harness away while pinching.

    Keep us posted.
    Fixing everyone elses boat just so I can use mine...

  3. #3
    Thanks for that, I just did a simple ohm test on the injectors...6 of them at 15.2 ish and 2 of them are at 30 and 35. I think you're right, seems like i have an injector problem. Appreciate the response. I will follow up.

  4. #4
    New problem!! I changed 2 injectors and the boat ran great for a couple hours. Then it just died like it ran out of gas. After testing, I have no fire, and also the ECM is not sending a signal for the injectors to spray. The ECM is not sending any codes - just the 12 to confirm its connected. What could have happened that immediately shut down the ECM from sending fire and injector spray?

  5. #5
    Join Date
    Aug 2010
    Location
    Long Beach, CA
    Age
    44
    Posts
    1,108
    Boat
    2015 Z3, 1999 2100i
    Wow! The ECM receives signal from the distributor ignition module when to fire the injectors. If you have an original ignition module (2 wire unit with no external ground wire) replace the ignition module and all will be fine. Mercruiser PN #87-892150Q02. All you have to do is pull the distributor cap, remove the rotor and then remove the ignition module and replace with the new unit.
    Fixing everyone elses boat just so I can use mine...

  6. #6
    Join Date
    Aug 2015
    Location
    Salt Lake City, Utah
    Posts
    1,593
    Boat
    2017 RZX3, 2013 MB F24, 2000 21V
    It's pretty easy to test the ICM with a meter. Here's the steps:

    https://easyautodiagnostics.com/gm/4...ed-icm-tests-1

    If you replace the ICM be sure to put dielectric grease between the ICM and the mounting base on the distributor. The grease helps pull heat out of the ICM. Its life will be shortened significantly if you don't.

    I have never had good luck with aftermarket coils. If you don't have a GM coil in there, I'd replace it with one.

  7. I actually replaced the ICM (before the problem) and then went back and installed the old one thinking the new one was the problem. Nope, still had the problem. After all of this, I replaced the ignition coil, then it fired right up. I reluctantly replaced the coil because I didn’t think the coil could cause both a no spark and no spray... but sure enough, the coil was the culprit. Thanks for all of the insight. Searching these forums has saved me a bunch of $$$$. Furthermore, it is great that I’ve had all of these problems so I could learn about the engine. Thanks again

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