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74L Mercruiser intermittently kills

S

scottpru

New member
"1996 Sea Ray Sundancer 290DA

"1996 Sea Ray Sundancer 290DA - 7.4LX Bravo MP 300HP. This has been happening for a few months now. Engine starts and runs fine, normal power and RPM's then it will just die... it starts up again no problem. It does it at high RPM's and low... it sometimes has a little fit and will die and start as many as 30 times in 10 minutes or so. It always starts right back up though. At some point it will just get over it's little fit and run fine for the next day or days, then unexpectedly it will act up again. I have run plenty of gas through it (400 gallons since it started acting up), changed fuel water separator filter, put additives in the gas in case of water contamination or something.

Anyone experience anything like this?"
 
"Ayuh,....

Sounds like the

"Ayuh,....

Sounds like the old Wiring Gremlin,.....

I'd try the equally old,+ somewhat reliable Shake, Pull,+ Wiggle Test......

You might get Lucky,.......And Don't forget the Grounds(-)........"
 
When it dies do the gauges als

When it dies do the gauges also go dead? Could be the key switch or wiring to it. The fact that it always starts back up sounds suspiciously like key switch related.

Rod
 
actually... i just can't r

actually... i just can't recall. but that is an excellent point and i will pay attention to the gauges next time. or maybe just replace the ignition switch that would be cheap and easy.
 
"You could gamble on the switc

"You could gamble on the switch, but here is the thing:
If the gauges are also dead, you know it's either the ign switch or something before it in the circuit. The switch is the likely problem.

If the gauges remain alive when it dies, then its not the ign switch, but something further along, likely in the engine wiring harness, or the 10 pin barrel plug where the boat wiring connects to the engine harness. These plugs can corrode and result in poor contact. The only thing is, when they go bad they usually stay bad.

Rod"
 
"ok... i paid close attention

"ok... i paid close attention to the gauges this weekend and they all stay powered on. the engine did it's thing again for about 40 minutes straight then worked fine for the next hour of running. it's not the ignition, and now it seems to start harder and when restarting it will sometimes backfires through the carb and smells like raw gas.

any other suggestions? anyone..."
 
"Just sharing a dilemma I had

"Just sharing a dilemma I had with a 5.0 Liter Merc I/O was about the same symptoms except sometimes I would have to let it sit for 10-15 min before it would start. I realized it happened when I washed down the deck. It ended up being water was dripping onto the top of the coil causing it to short (combination of a bad coil to distributor wire). Not saying this is your problem, just some food for thought."
 
"scott;
Since the gauges stay

"scott;
Since the gauges stay hot the next prime suspect is the 10 pin barrel plug.
I would disconnect the battery, then take the plug apart, and thoroughly clean all pins and receptacles til they are shiny.

One thing that works well to clean the receptacles is a small brass gun cleaning brush, the size used for a 22 caliber or a pellet gun seems to work well.
Then reassemble and clamp. You can use a light coating of grease to keep he corrosion at bay.

Rod"
 
the motor was tuned up this sp

the motor was tuned up this spring prior to launch. i told the marina about the problem and they said it didn't display any problems for them. i have checked for water around the ignition coil and other areas but all is very dry. i have had the 10 pin barrel plug opened and i spread the male pins for a better connection but did not attempt to clean the pins or the female plug side. i think i'll go back and do the cleaning of both.

thanks again for all of your feedback!
 
"The marina likely ran it for

"The marina likely ran it for about 3 minutes and so it did not have time to misbehave for them. This is not to detract from dealers BTW; it's just that they are usually very busy and don't have the time to spend on every single boat issue.

You have an intermittent electrical issue, and the barrel plug is certainly the next logical suspect along the line. Just my opinion.

Rod"
 
i agree... i didn't expect

i agree... i didn't expect them to find it unless it was in the tune up. but since it is so intermittent it has been a problem... especially when it happens when i'm docking. barrel connector is next on my list.
 
I'm having the same proble

I'm having the same problem. Were you able to resolve this? I was about to try swapping out the ignition module.


1996 Thunderbird Falcon/7.4 BIII.

Bob
 
"no we're still looking. i

"no we're still looking. i have ruled out loose wires since everything has been pulled tugged cleaned and checked. i've had a mechanic looking at it and it will sit and run for minutes in the slip then just stop running, start quickly then again stops... no sputtering no missing just stops. he's coming back with all the electronic hookups so hope to know next time. i'll keep you posted of course."
 
"Had similar problem on a VW s

"Had similar problem on a VW some time back. It may not even begin to relate to your problem, but my problem was eventually traced to a failing alternator. It took about a month to find solution."
 
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