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Mercruiser 5.7L stalls on acceleration
Confusing problem. Had a coil short while underway and accelerating.
Would not restart. Was towed in. Tested the coil (lifted the negative
wires and showed short on both posts). The coil was the original (17
years old).Replaced the coil with OEM part, spent the rest of the day cruising
with no problems. The next day, the throttle release broke and I took
the remote control apart and replaced the broken plastic part and
reassembled. Took the boat out and upon acceleration (climbing past
3000 rpm's) the engine bogged and shut off but this time, it restarted.
Idled around a bit, reved up again, and at around 3000 rpm's, it shut
down. Restarted and idled back into port. Reving the engine out of
gear does not cause the problem, only under a load. Even though I had the coil problem, since the last thing I was messing
with was the remote control assembly, I highly suspect the something
related (interupter switch on the engine?). I noticed the top cable
was parting at the crimp connection and the cable would pop in and out
of the crimp on movement. Also, the bottom control cable was flopping
on forward/reverse movement of the throttle. Questions: Is it possible that the bad cables are causing the engine to
shut off at 3000 rpm under load only? Could this problem have
originally killed the old coil? Is it possible to but a meter on the
interupter switch and watch for opens when moving the throttle to full? |
bayplyer
Oct 7
2005
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| Thanks Jeff. After scouring the newsgroups, there seems to be numerous
problems that match to the symptoms. Most folks say the majority of
problems are ignition circuit related, unless you suspect this in which
case, the problem is fuel related??? The first three in the list are
ignition related... 1. Arcing in the plugs, secondary wire, or distributor
Inspect/clean replace
2. Coil breaking down
Swap
3. Shift interrupter, cable tension
Disconnect and test underway
4. Fuel accelerator pump/varnished carb
Replace/soak
5. Vacuum in the gas tank, lines
Remove cap to test, clean vents
6. Water, debris, bad gas
Check filters, fuel seperator, clean or drain I've already done 2 and I can probably test 3, 5, and 6 without messing
anything up. After that, I'll probably get some help. |
bayplyer
Oct 8
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| I agree with your suspicion about the shift cable being a possible source of
the trouble. Temporarily disconnecting the interupt switch would be an easy
and positive test to confirm. "JIMinFL" <jiminfl@earthlink.net> wrote in message |
JamesgangNC
Oct 8
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| If you ignore everything in your post but the symptoms, it sounds like a
carburetor problem. I had the same thing. Need to disassemble and soak in
carb cleaner then flush the jets and passages with a can of carb cleaner. "bayplyer" <jeff.brunell@iname.com> wrote in message |
Jeff
Oct 8
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| I'm no mechanic, but it would seem that you'd be pushing much more cable through
the line to reach 3000rpm under load than you would in neutral. Your description
of the cable parting doesn't sound good. --
John H "The trouble with our liberal friends is not that they're ignorant: It's just that they know so much that isn't so." Ronald Reagan |
PocoLoco
Oct 7
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| I always suspect the things that were worked on last. Alphas rely on the
drive's desire to stay in gear to activate the interupt switch. It is the
tension that builds up onthe cable housing that activates the switch. This
makes the behavior different when the engine is not running. Among other
things that's why they are such a pain to adjust. The interupt switch is
only for getting it out of gear so you can disconnect it temporarily for a
test. I would suggest you get to open water, disconnect the interupt
switch, then test your theory. It can be a bear to get away from the ramp
or dock without it. You will need to turn the key off to get it out of gear
so be prepared to do that. "bayplyer" <jeff.brunell@iname.com> wrote in message |
JamesgangNC
Oct 7
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| Sounds like the cable tension is critical and I need to replace them.
Will I run into the cable adjustment brain damage by replacing the two
cables that run from the remote control to the parallelogram? |
bayplyer
Oct 7
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| The service manuals have very specific instructions for how to adjust the
shift cable and the switch after you replace it. A lot of people have
trouble with it though. Imho it's a bit of a rig. I'm surprised they
couldn't figure out something more straight forward. In theory accelerating is not supposed to have any effect, The control
should only be moving the throttle cable once it has shifted into gear. The
throttle cable is completely independent of the shift cable and is easy to
adjust. But since you already had cable trouble I'm still inclined to
suspect it first. "bayplyer" <jeff.brunell@iname.com> wrote in message |
JamesgangNC
Oct 7
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| The cables can be mis adjusted so that there is movement in the shift cable
after the drive is in gear. this will put tension on the interrupter lever
and it could trip the interrupter switch. Often people try to compensate for
worn or damaged linkage and sterndrive parts by misadjusting the cables.
This could lead to more problems. When everything is in good mechanical
condition, the cables are easy to set up. |
JIMinFL
Oct 7
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