Sputter at 3000rpm, TBolt IV 1988 454 Magnum
#12
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I had a 502 with a circa 1990 ignition setup. Odd miss at 3500 to 4k, came and went. Changed or rotated out with known good ignition components and eventually I disconnected the tach wire. Problem solved. Apparently, something in the tack was pulling the signal down at certain points in the sweep. At the time I re-connected and tested again to verify the cause. It was repeatable. From asking my buddy who was a very good marine mechanic he did say it was an uncommon problem but he had seen it before. Not certain if related to specific tach brand. Simple to try.
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SB (08-04-2024)
#13
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Did some google searching seems that is a more common problem now with that era of boat. Tachs are getting old. Simply pull the gray wire at coil and test.
Is problem dead repeatable at X exact RPM each time? From my symptoms some years back it seemed to come and go but a tach shorting to ground would likely not be totally repeatable and likely temperature, vibration humidity, etc related or affected. Let us know what happens...
Is problem dead repeatable at X exact RPM each time? From my symptoms some years back it seemed to come and go but a tach shorting to ground would likely not be totally repeatable and likely temperature, vibration humidity, etc related or affected. Let us know what happens...
#14
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Thread Starter
Will pull tach wire and report back. Coil on order. Dist pickup next.
Thanks, will get there.
Thanks, will get there.
Last edited by Pismo10; Yesterday at 02:19 PM.
#15
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Had a customers boat whom’s coil issue would cause engine to die after same amt of time, every time.
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105Fountain (Yesterday)
#16
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Let us know what it was?
#17
Charter Member # 55
Charter Member
I would start with replacing the coil and if no change, then the pickup module Mercury-Mercruiser 87-892150Q02 SENSOR ASSEMBLY Genuine factory part (mercruiserparts.com)
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mike tkach (Today)
#18
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tgnition coil,s don,t last forever,also the coil wire carys rhe load 8 times more than each plug wire,i have seen a coil wire cause strange issues.
#19
Platinum Member
Platinum Member
Hey Mike good to see you're still around
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Griff (Today)