Join Date: Jul 2007
Location: Truckee, CA
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Re: Johnson 3.5 running a bit groggy
Lots of possibilities, suggest you start with the easy things first:
1. Replace the fuel with fresh and add the recommended dose of fuel additive, I have used Berrymasn's B-12 Fuel additive for many years with no fuel related problems.
2. Treat it to a new set of properly gapped plugs
3. Check all the electrical connections for corrosion or looseness, and all the fuel fittings for possible air leaks, including the carb / manifold fittings for tightness
4. Try setting the low speed mixture while running, turn counter clockwise until the engine starts to stumble, then back clockwise just until it smooths out, no more. Or you could just turn it in all the way then back out about 1-1/2 turns and start from there.
5. Assuming it is timed properly and it has been sitting for a while there may likely be debris in the carburetor. As a last resort, remove and thoroughly clean all the parts, blow out the passages with carb cleaner spray, then with compressed air.
6. You can probably download a shop manual on a Google, or equivelent, search.
Let us know what you find.
Forgot this, check all the fuel filters, including the one behind the fuel pump, if it has one.
Last edited by dabnis; 08-25-2012 at 06:43 PM.