engine cutout

[sundancer]

hi all.
my mercruiser 4.3 has a intermittant, and frightening, way off stalling/all most cuts out then runs badly/ lumpy.
my good lady noticed that it usually seems to happen in choppy/rough waters but elsewhere runs really well.
after previous horror story ie called RNLI out who escorted us back into nearest marina, i changed plugs, coil (leaking), rotor arm, dis cap and fuel filter.
I APPRECIATE THE PROBS OF INTERMITTANT FAULTS (hard to locate etc)
could it be anything to do with trim and water coming in. only other suggestion is that occasionly the bilge pump alarm comes on for a few seconds but no signs of large amounts of water in engine compartment.
ps.boat is 22ft searay

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[chippie]

The fact that it happens in choppy conditions points to the possibility of crud being picked up in the fuel feed or the feed sucking air. Did the fuel filters have much crud in them when you changed them?
Does any water get onto the motor or wiring? Check all electrical connections for tightness.
As you realise, its about eliminating possibilities.

Good Luck

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[sundancer]

thanks chippie.
no to my suprise the filters were very clean and i have checked for lose wiring.
i wondered if possibly somehow it was a "following sea" that might cause it the only common feature here is it happens when it gets a bit choppy.
thanks again


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[Heckler]

once had a tvo/petrol tractor for launching boat, when it got quite deep the tip of the fan blade touched the water and sent a fine mist over the distributor, the dizzy cap then arced and it misfired,
question are you getting any water near the coil or distributor from the following seas, the prob is not fuel related, cause in a petrol engine if you get water in the fuel it inevitably ends up in the carb and the prob doesnt go away
stu

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[ccscott49]

Dont those engines have a switch on the throttle, which shuts the ignition down, mometarily when you change from frd to astern? Could that be a problem? I'm not sure, but something in the old grey matter is stirring about this. But it does sound like some damp/spray is getting at your electrics, on the high tension side I would think.

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[ballena]

We had a Searay 200 with 5.0 V8, it used to cut out in rough water as we got further down tha tank, even in calm seas it would begin to cut at lower and lower revs, we sold the boat so never got to the problem.

Did all the same things that you have done with no difference, the only thing that I did notice was that after disconnecting the fuel feed to the pump and blowing back into the tank, the problem went away for a while,might have been crud in the tank blocking the filter.

Have you replaced the anti-syphon valve in the tank line?

Let us know how you get on

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[sundancer]

ta for your reply.
we struggled back into calmer waters on low revs and eventually back to our berth
but whenever i tried to increase revs the engine tried to stall thern would increase and back again.
while moored i could rev the engine as far as i liked 5000 + but when in drive
problem would return.

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[chippie]

One other thought :-does the fuel tank breather some how get blocked?

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[sundancer]

thanks for your advice.
i had a interesting chat with the marina owner who sold me the boat last month.
he will repair any faults but as he rekons the boat was sold as brokerage he considers himself free from any obligation.
ummm. nice chap when selling to me. now that he has my money !!!!!!

anyway, got a boat mec who says almost def dirty fuel.

ta again


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[yoda]

You could be suffering from water in the fuel. If the fuel take off isn't right at the bottom of the tank it is possible for water to build up (from condensation ) and in lumpy conditions be sucked into the fuel line. A quick dose of water dispersant sold at good chandlers will get rid of the water. Spent years trying to sort out a similar problem for it to be solved by my mum reading a few bottle lables in the chandler! If it isn't water then a dose of the stuff won't do any harm anyway so nothing to lose.

Yoda

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[Heckler]

the prob is happening when you load the engine and that is indicative of an ign problem. when you load the engine the ignition system has to "work harder" and one of the hi tension components is breaking down under load.
it is a bit like the tractor prob or an even better example was the mini in driving rain, the water would get on the distributor and cause it to start arcing, if you put your foot down and loaded the engine it would start to cut out but if you feathered the throttle it would keep running.
check out the distributer cap, coil top and hi tension leads, see if you can see any sign of arcing, dont forget that if you have had salt water on any of them that the salt will still be in the nooks and crannys and that it is hydroscopic and sucks in moisture from the atmosphere and will replicate the problem again and again
stu

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[sundancer]

ta yoda
i will try that
good luck too you


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[sundancer]

ta for that.
food for thought
got a kind man looking at poss fuel probs, ie dirt but it is interesting what you say
and you have now given me a restless night.
bon voyage
james


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[ArthurWood]

Sonsy - But why does it only happen in bumpy conditions? Still sounds to me like water/crud in fuel.

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[Heckler]

dunno but i stand by what i say about crud in petrol, if it gets in it doesnt go away once in the carb,
stu

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