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Troubleshooting 1997 Mercury 90 2-stroke
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ContinuousWave Whaler Moderated Discussion Areas
ContinuousWave: Whaler Performance
Troubleshooting 1997 Mercury 90 2-stroke
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| Author | Topic: Troubleshooting 1997 Mercury 90 2-stroke |
| skookum point |
posted 10-02-2006 03:03 PM ET (US)  
It’s a 1997 Mercury 90hp 2-stroke on a Montauk and it runs rough under load at 2200 rpm and under, otherwise it performs normally. The motor has very low hours, good even compression and starts easily. And at idle, in neutral, it's about as smooth as you would expect from a Merc. First I replaced the plugs – no change. Next I rebuilt the already squeaky clean carbs and there was no change. Then I adjusted the idle mixture screws - best idle is at 1-1/2 turns. I messed with the idle screws some more with the boat in gear and running at 1500 rpm but it wouldn’t smooth out. Next I checked the timing and link/sync and everything was right on the money as described in the Merc Service Manual. Then I used a spark gap tester and got a good spark that jumped the specified gap on all three at cranking rpm. So far I haven’t been able to deduce whether it’s ignition or fuel related and I’m running out of ideas. It's smokey while running rough, is that a clue? Any advice before I take a chance and potentially waste a bunch of money on new CDM’s? |
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