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Thanks to all for the help...I won't be able to test all the suggestions for a couple of weeks but will post results when I do. Again...thanks!
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:coolcowboy: Thanks to everyone who tried to help, but my tach is still giving it up at 4K like in my original post.
Originally Posted by firehawkcat
(Post 3467345)
All tachs work on 4,6,8 cylinders. make sure you are on the 8 cylinder should be a button or switch on back of tach
Originally Posted by blue thunder
(Post 3467355)
I see the problem. Your negative (tach) wire that goes to the coil is too close to the coil primary wire and/or plug wires.
Originally Posted by David Stotz
(Post 3470321)
TS27,
Sorry I didn't get back sooner. The reason I asked about ignitions is I chased the same demons with an MSD set-up. I thought the factory guys were giving me a line when they told me the tach trigger wire was being affected by the high energy output of the ignition system. They said to make sure the trigger wire was well isolated. After trying everything I thought would solve it I took their advice. THEY WERE RIGHT! Sounds like you have a similar problem. Dave
Originally Posted by GAUGETHIS
(Post 3471324)
Thunderstruck is exacly correct. It is a loose wire to the negative side of the Coil ground or bad/ loose spark plug wires. Also check the ground on the coil. It gets its ground from a bracket and if the bracket is not grounded hence the iratic signal. Hope this helps Good luck
Originally Posted by Steel Outlawed
(Post 3474461)
firehawkcat: I can't find any buttons or switches but the tach is a new Livorsi and I specified 8 cyl when I bought it... blue thunder: I got rid of the plug wire birds nest and rerouted the coil wire away from the neg. tach wire as far as possible...no help. David S.: I'm not sure what you mean by the "trigger wire" (maybe the Neg. tach wire to the coil?). How do I isolate it? GAUGETHIS: Had already checked the Neg. coil wire. I ran a 10 gauge wire from the coil bracket to my battery ground...No Luck. Checked the plug wires for good connection and they're fairly new...there may be a suppression problem but can I test them without buying a new set of wires... Steel Outlawed: I ran a ground from the distrbutor cap screws to the battery ground...didn't help. Is it possible my plug wire are putting out too much noise and interferes with the tach once I get to 4K? HELP...I need an RPM reading at WOT so I can get my blade tuned. Thanks again your help and advice. |
Originally Posted by Thunderstruck27
(Post 3497786)
:coolcowboy: Thanks to everyone who tried to help, but my tach is still giving it up at 4K like in my original post.
OK guys...This is what I did last weekend. firehawkcat: I can't find any buttons or switches but the tach is a new Livorsi and I specified 8 cyl when I bought it... blue thunder: I got rid of the plug wire birds nest and rerouted the coil wire away from the neg. tach wire as far as possible...no help. David S.: I'm not sure what you mean by the "trigger wire" (maybe the Neg. tach wire to the coil?). How do I isolate it? GAUGETHIS: Had already checked the Neg. coil wire. I ran a 10 gauge wire from the coil bracket to my battery ground...No Luck. Checked the plug wires for good connection and they're fairly new...there may be a suppression problem but can I test them without buying a new set of wires... Steel Outlawed: I ran a ground from the distrbutor cap screws to the battery ground...didn't help. Is it possible my plug wire are putting out too much noise and interferes with the tach once I get to 4K? HELP...I need an RPM reading at WOT so I can get my blade tuned. Thanks again your help and advice. |
I put a new Livorsi tach into a boat I owned about 6 - 7 years ago - 502mag mpi. Fought the same problem as you, and ended up buying a tach filter from Livorsi, which solved the problem.
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I talked to Fred at Livorsi yesterday about a filter for my tach. He said the only filter they have will only work on their older tachs with numbers beginning with "GW". So of you got a filter to fix this problem on anything other than the "GW" model it isn't going to work.:eek:
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Did you try replacing the coil ? :drink:
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I have had a bad merc ignition module that ran fine but sent a bad signal to the tach above 3k...
Swapped modules and problem solved.. |
What are you volt meters showing ?
Try connecting a #10 guage wire from your alt to the main power on the starter . some of the old wiring harness's don't have this or if someone monkeyed with it . Just had a boat do the exact same thing your saying and this fixed the problem. Tom |
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