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5.7 misfires after hour run time

A

Anchor8600

New member
[FONT=&quot]Hello, I have a ‘99 Searay signature 230, 5.7 merc., 400 hours. Recently tach jumped all over and engine misfiring. Tach erratic with no change in engine as well.[/FONT]Only does this after 1 1/2 -2 hours running time. Idles perfect. Runs perfect for short excursions.
This spring had I new distributor, rotor, ignition wires and plugs done as preventative maintenance.
Did not have any issues prior to tuneup. Have since replaced the ignition coil. Unhooked tach. Put another new dist. Cap on as it was showing some signs of corrosion after just a few weeks. Still get misfire at 2000 rpm, but only after it has run perfect for an hour. Starts fine ,idles great, no stalls, perfect to 2000 rpm’s then starts missing.
Any thoughts, suggestions?
Thanks
 
Have you checked your ground strap/negative cable for tightness/cleanliness? Same for your starter and battery connections. Take them off, clean with stainless steel wire brush. Reconnect and generously grease them. If you are still having issues after that, then we can better troubleshoot.
 
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