Mercruiser &.4 on 1997 bayliner 2858 runs good for 15 minutes, then instantly loses RPM and power, Floods, backfires, "misses" (plug wire removal test shows it is sometimes runs on only 5-6 cylinders); press electrical switches like trim tabs and RPM -power changes dramatically. Can also instantly regain power. Often surges. All gauges show normal ranges.
Ran perfect before boat hauled last fall and engine removed and upgraded by mechanic: installed new fuel pump, plug wires, plugs, exhaust manifolds and risers; fuel lines; etc. Mechanic diagnotic computer shows no error codes. We are stumped. Need help. Appreciate suggestions.
2007-08-13 12:34:49 · 7 answers · asked by Anonymous in Cars & Transportation ➔ Boats & Boating
Sounds like a loose wire on your ignition somewhere, possibly a faulty interrupt switch. This switch momentarily kills the ignition when shifting into gear to make shifts smoother. If it is faulty, it could cause the symptoms you describe.
2007-08-13 12:55:39 · answer #1 · answered by Campo 4 · 0⤊ 0⤋
Disconnect the tack wire an try running mercury has an problem with tacks shorting out a Engine runs terrible have replaced 4 so far>Hope this helps???Run a test red wire from the battery to the ignition switch hot lead might be getting low voltage . When they put the wiring together they run everything off the panel an over time adding more stuff it takes power from the eng. These are 2 common items i have found over yrs of trouble shooting ele???
2007-08-13 22:06:52 · answer #2 · answered by 45 auto 7 · 0⤊ 0⤋
I believe the answer regarding loose ground is what you should be looking for. If you have 7.4 engine there is no interrrupt switch on this as you probably have a bravo drive on it.
Go behind the engines bellhousing and you will find it bolted on both sides with a stud .Check all grounds to make sure they are tight using deep 9/16 socket.
Also check the main engine harness connector at engine and make sure you have good connection and clamp is snug. Some people have a habit of overtightening the connectors hose clamp and it distorts the pins where they go into socket and makes poor connections.
Also make sure the battery connections are tight .
Mercury has service bulletin out that states replace wing nuts on batteries with nylock nuts. Hope some of these suggestions help
2007-08-13 20:52:36 · answer #3 · answered by paultech6 4 · 0⤊ 0⤋
Is the alternator putting out good?Sounds like you are losing voltage to critical components when trim is initiated.Make sure your fuel tank is vented and not pulling a vacuum.Try loosening the fuel cap and running.
2007-08-13 19:58:00 · answer #4 · answered by gdwrnch40 6 · 0⤊ 0⤋
check ignition module MSD if its not hooked right it foul ing timing and rpm Gage will freak out . look at the wire in the dispt cap . from rpm gage .and check pick up coil . and voltage regulator in alt ,
2007-08-13 21:24:00 · answer #5 · answered by daniel h 2 · 0⤊ 0⤋
when a qualified mechanic tests all systems to be okay, hopefully more than once, it's the "magic box". the ECM can fool any computer or DDT. i've seen it with all kinds of engines.
2007-08-14 10:58:51 · answer #6 · answered by Anonymous · 0⤊ 0⤋
loose or bad ground, or ground left off by the mechanic.
2007-08-13 20:27:08 · answer #7 · answered by Anonymous · 0⤊ 0⤋