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What the Hell is That?
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So I was out this weekend. Boat idles fine, Tach is correct as least I think. The problem is under load it will be at say 3500 then drop to zero then shoot back up. at even higher RPM it will stay at 0 until I let up off it. I don't think its a short problem cause most of the gauges are piggyed back together and the Amp meter doesn't show an Excessive load (been there done that with a shorted water temp gauge) I believe its either the Coil (Mallory Promaster) or the Ballist resistors going bad. Tach is a brand new SW tach.

Any insights?
 

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What the Hell is That?
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1,633 Posts
Discussion Starter #2
anyone?
 

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Double check the ground. Many tach problems in boats are due to bad grounds.



Darrell.
 

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custom boat lover
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498 Posts
So I was out this weekend. Boat idles fine, Tach is correct as least I think. The problem is under load it will be at say 3500 then drop to zero then shoot back up. at even higher RPM it will stay at 0 until I let up off it. I don't think its a short problem cause most of the gauges are piggyed back together and the Amp meter doesn't show an Excessive load (been there done that with a shorted water temp gauge) I believe its either the Coil (Mallory Promaster) or the Ballist resistors going bad. Tach is a brand new SW tach.

Any insights?
Here is a few other little ideas to kick around also, It's some links that talk a little bit about tacks.http://forums.iboats.com/showthread.php?t=308377&highlight=tack http://forums.iboats.com/showthread.php?t=314439&highlight=tack here is a new test i have never heard of before see the batt charger idea. hummm http://forums.iboats.com/showthread.php?t=269141&highlight=tack
 

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What the Hell is That?
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1,633 Posts
Discussion Starter #5
I don't think its the GRND but I will check it. The Ground on the Tach is also hooked with another ground to the water temp. The water temp reads fine. The coil + ballest resistors are 10+ years old. I also noticed cracking on the resistors.

Maybe the tach needs its own dedidacted gound? I replaced the old tach becuase of this problem (I thouhgt the tach was bad) It started this problem after the boat say for a long time.
 

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i have kind of the same problem but my tach seems to idle well , but when i go wot it pegs the needle,if i check it with a battery charger what would you check it on the 2amp or 10 amp? or what would cause it to peg at 6 grand??
 

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Sitting for a long time also sounds like a ground ploblem. Corrosion.
Run a long wire from the Tach to the Neg side of the battery. Just lay it alongside the seats, temporary. Don't put anything else on this wire.
Does the engine miss or act up when the tach goes nuts? If not, the wire from the coil/points to the tach may be bad. Do not connect it to the ballast resistor. Run this wire straight from the points side of the coil to the tach. No other wires on it. Good luck.
 

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What the Hell is That?
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1,633 Posts
Discussion Starter #8
Sitting for a long time also sounds like a ground ploblem. Corrosion.
Run a long wire from the Tach to the Neg side of the battery. Just lay it alongside the seats, temporary. Don't put anything else on this wire.
Does the engine miss or act up when the tach goes nuts? If not, the wire from the coil/points to the tach may be bad. Do not connect it to the ballast resistor. Run this wire straight from the points side of the coil to the tach. No other wires on it. Good luck.
No points, Its electronic ignition well a points conversion. The boat does pop thru the carb every now and again but I assumed that was something else. I have never seen the tach when the pop occurs. First instinct is to look back I guess. It will give me piece of mind to replace the coil and resistors hell they couldnt hurt. If it still happens at least i have it narrowed down somewhat.
 
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