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Old 12-06-2006, 11:41   #16
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It sounds like feed back. I would GUESS it's in the altenator, regulator or the tach itself. A diode as mentioned before.

When you shut down the motor the engine is still spinning, producing power through the altenator. By turning the key back on then off again the power flow has stopped allowing the system to shut down.

? Where is the power source to the tach connected??? It should be the "I" termenal of the ignition switch.
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Old 12-06-2006, 13:52   #17
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On a gasoline engine (since you use the ignition to shut it I'm assuming it's gasoline) the tach lead may go to the ignition coil, OR to a tach terminal "T" on some alternators, and I'm sure to some other creative places. OR to a dedicated sensor adjacent to the flywheel, more likely on a diesel engine.

Of course, if you rip out the tach, the boat will be faster and lighter, better for racing.<G>
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Old 12-06-2006, 22:06   #18
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The engine is a diesel.

I don't believe the problem is the use of wrong terminals on the ignition key. I've had the boat for 6 years and it work ok originally.

Some thing has changed over time and I suspect it is something to do with the diodes, maybe one has blown or is faulty.

Its one of those things which is anoying but not "sail stopping".
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Old 13-06-2006, 08:03   #19
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"Its one of those things which is anoying but not "sail stopping"."

If it IS a bad alternator diode, it is damaging your electronics gear every time you rin the engine with spikes of reverse polarity that may or may not be stressing everything in the system. Hard to say with any certainty how much damage is being done, only that it may be done.

In which case, it won't stop you from sailing--but you wouldn't want to run the engine until it was checked, unless you wanted to replace any electronics on board. (Ka-ching!)
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Old 09-11-2006, 13:23   #20
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I just got here so I may be completely wrong, BUT.....if its a diesel engine how are you turning it off with a key? And if you are turning the key off before pulling the fuel cut off you have probably blown at least one of the alternator diodes id not all of them. A diesel should be stopped before you turn off the key or you will blow the alternator because it will be unloaded when the key is turned off.
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Old 09-11-2006, 15:10   #21
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if its a diesel engine how are you turning it off with a key?
Some will and some won't. My Perkins won't and my Westerbeke will. Two Brits of a differnt color. Percy and Winston as they are know around here.
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Old 09-11-2006, 18:37   #22
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Originally Posted by jimisbell
I just got here so I may be completely wrong, BUT.....if its a diesel engine how are you turning it off with a key? And if you are turning the key off before pulling the fuel cut off you have probably blown at least one of the alternator diodes id not all of them. A diesel should be stopped before you turn off the key or you will blow the alternator because it will be unloaded when the key is turned off.
My new Volvo can only turn off with a key. There is no fuel shutoff. Bit like a diesel car I suppose.
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Old 09-11-2006, 21:03   #23
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Some will and some won't. My Perkins won't and my Westerbeke will. Two Brits of a differnt color. Percy and Winston as they are know around here.
Interesting, my Perkins 4-108 wont and my Volvo 2003M wont and my Perkins 6-354 wouldnt. I was not aware that there were those that would unless they were on a car.
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Old 09-11-2006, 21:16   #24
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Some engines have an electric solinoid fitted to the the injector pump, exactly where the pull stop would normally be fitted. A Solinoid can be fitted to any Diesel, but there are the odd few that come factory fitted. There are also a few that have an additional fuel solinoid shutoff valve as well.
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Old 12-11-2006, 09:29   #25
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Leighton;

Does your key-switch have position labels? What do they read left-to-right? My Perkins 4-108 has a key-switch labeled (left to right) "Off-On". But it has separate start and stop pushbuttons. The start button engages the starter and the stop button engages the stop solenoid (attached to the injector pump). Neither works unless the key-switch is in the "On" position but the engine will (once started) continue to run even if I return the key-switch to the "Off" position (but then my tach won't work). Will your engine continue to run with your key-switch in the center position? Will your tachometer register?

Is it possible that your three position key-switch engages the starter when turned to the far right and engages a stop solinoid when turned to the far left? In both instances the key-switch should return to the middle position when hand pressure is released. If the circumstances I've outlined above are true, then you may have a defective key-switch or the original key-switch has been replaced by one that does not return to the center position automatically.

This may be why " ... rev counter stays at about 700 rpm even with the engine stopped. If I leave it like this it will drain the battery overnight." The battery drain may be caused by current flow through the stop solenoid coil and have nothing to do with the tachometer at all.

If this isn't it, at least it's something to eliminate.
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Old 12-11-2006, 14:27   #26
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good possibility...BUT, unfortunately I dont have a key. All I have is a pull switch that turns on the battery to the instruments etc. and a button that engauges the starter. When I let go of the button the starter dissengages. If I push in the electrics switch it shuts off power to the engine gages. I only do that after pulling the fuel cut off.
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