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Need help with vibration

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bpage4110

New member
Ok the other day I went out in the waterway drifting for flounder and while im in idle or going verrrry slow my motor vibrates pretty bad and the fishing poles are shaking real bad is there anything I can do to fix this problem?


1994 8hp mercury 14 ft jon boat
 
If the vibration is really, really bad, one of the flywheel magnets
may have moved....there are two of them and they should be
180 degrees apart from one another (underneath the flywheel).
If this is it, the vibration would occur at all engine speeds...not just idle.
 
Two things you can do if it's "mechanically sound" (so not the prop etc).

1) install a thermostat (with a gasket - not included) - these shipped from factory without a thermostat on many model years - it will idle considerably smoother with a thermostat in place

2) replace the OEM coils with the cross-ref'd coil from Sierra (and specifically Sierra). Merc used to sell a "high voltage" conversion kit for these that would allow them to use the higher powered coils found on models above 25 horses. They also smooth things out at idle/lower rpms "noticeably".

The only difference in the coils (save the power they throw out) is how they are mounted - the higher horse ones go in a holder, the 25-under mount with a bolt through the middle of the coil. The Sierra coils only come in the higher voltage and they contain the mounts for all styles of mounts - as an added bonus they are less than half the cost of OEM (25'ish bucks each last ones I bought) - Sierra # 18-5186 - good for 6/8/9.9/15 horse models and others.
 
What rpm are you calling very slowly?if it idles at 7-800 in neutral smoothly and vibrates when you put it in gear and smooths out quickly as you increase throttle slowly then its a merc...it would be interesting to see what the coils mentioned by Graham would do....
 
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