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Old 08 June 2011, 02:53   #1
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Strange engine cutout

Engine (Mariner 50 2-stroke, late 90's) had run normally all day, then died on throttling back and would not start again (spun freely on the starter but would not fire) for about 20 minutes - at which point it suddenly started working again. However there seemed to be nothing coming out of the telltale, so we shut it down fairly quickly. After that, it refused to start again. Throughout, there was no overheat alarm and temperature guage stayed normal.

Got it ashore and in a water vat and it started and ran normally, telltale flowing fine! Any ideas what might have been going on please? Trying to work out the linkage if any between the starting problem, lack of telltale, but absence of any other overheat indication...

Thanks!
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Old 08 June 2011, 03:13   #2
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Engine (Mariner 50 2-stroke, late 90's) had run normally all day, then died on throttling back and would not start again (spun freely on the starter but would not fire) for about 20 minutes - at which point it suddenly started working again. However there seemed to be nothing coming out of the telltale, so we shut it down fairly quickly. After that, it refused to start again. Throughout, there was no overheat alarm and temperature guage stayed normal.

Got it ashore and in a water vat and it started and ran normally, telltale flowing fine! Any ideas what might have been going on please? Trying to work out the linkage if any between the starting problem, lack of telltale, but absence of any other overheat indication...

Thanks!
Blockage in a waterway? Buzzer not working? DOes it beep when you turn the key on?
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Old 08 June 2011, 05:47   #3
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Intermittent stuff like that I'd be going through the entire electrical loom (remotes box included) checking for loose connectors.

My old Yam refused to stop not long after I bought it - the bullet connector for the deadman had shaken loose -after me succesfully testing it in the marina before I left!
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Old 08 June 2011, 10:46   #4
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I'd suspect something along the killswitch as well. Maybe as simple as a partially inserted kill cord?

I'd guess the lack of telltale was a red herring; check it out more thoroughly once you get the motor firing again.


Luck;

jky
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Old 08 June 2011, 18:26   #5
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Thanks - but no, the buzzer works, as does the temperature gauge and neither raised any alarm - while if the killcord isn't in it won't turn on the starter (which it did). So the mystery deepens - I guess as you say it may be a case of having to check through the whole wiring....
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Old 08 June 2011, 19:00   #6
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Thanks - but no, the buzzer works, as does the temperature gauge and neither raised any alarm - while if the killcord isn't in it won't turn on the starter (which it did). So the mystery deepens - I guess as you say it may be a case of having to check through the whole wiring....
Are you sure? Most kill cords simply dissable the spark plugs not the start circuit. (Start in gear protection on the otherhand will give you nothing). My mind would also be on the faults being unrelated.
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Old 09 June 2011, 02:50   #7
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Sorry, of course you're right, scratch that about the kill cord and the starter, I was typing too late at night and talking bollox!

The pattern of refusing to start for some period (like 20-30 minutes) and then firing up had me wondering about some sort of ignition cutout circuit linked to any problems with the cooling, but AFAIK there's no such circuit, just the alarm and temperature gauge, yes?
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Old 09 June 2011, 04:12   #8
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Mariner 50hp

Check the HT leads to the spark plugs, and of course the spark plugs themselves including the gap. Is there any carbon build up or are the plugs fouled?

If you're satisfied it's not an electric issue, broken or loose wires, then it could be fuel related. It could even be as simple as the fuel tank wasn't vented - happed to me and had me stumped for 5 minutes. Then of course there's the fuel pump, could be a damaged diaphragm, etc.
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Old 09 June 2011, 11:04   #9
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your problem sounds electrical, check the spark plugs are they all the same colour are there any sparkly (very small) bits on the spark plug/s if so p/h seized? check for a nice blue coloured spark with a spark checker,spark is orange clean and check all electrical connections including the earths, no spark on any plugs, if it is the square type cdms they need to be checked by a dealer as he has the test harness and specs in the service manual, i have checked cdms without the harness and its a pain in the butt, has it got a black stator if so do a stator elcectrical voltage test,
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