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I have 1980 evinrude 175 carburetor outboard. I have had the…

I have 1980 evinrude 175...
I have 1980 evinrude 175 carburetor outboard.
I have had the carbs rebuilt no at 1300-1400 rpm
there is a bad flat spot so bad the motor well stall.
when the motor starts to stall I push in the choke
it will run o.k.
Help.
Jim.
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Answered in 41 minutes by:
6/26/2010
Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4,730
Experience: 42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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Welcome,
I will be happy to assist you. If you have a question or need clarification please post back at any time.
From your description the synchronization of the linkage between the carbs and ignition is wrong. The ignition timing should be advancing quite a bit before the carbs begin to open. This would be consistent with not checking the linkages after the carb rebuild.
On the side of the carbs is a metal plate with slotted screws. At idle, engine off, loosen each of these screws. operate the carb linkage and allow it to snap shut. Carefully tighten the screws. This will ensure all of the carbs open at the same time.
The throttle cab pushed against the carb roller to open the carbs. The cam should just touch the roller at the lower embossed mark just as the carb linkage begins to open or move.
This should get you in the ballpark.
Let me know the results.
Jeff
Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4,730
Experience: 42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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Customer reply replied 8 years ago

After rereading I don't se how your answer helps me with my 1300 rpm flat spot

sorry am I missing something ??

JIm.

When the engine is at idle or just slightly above it works fine, the interaction of the timing and carb opening (fuel/air mixture) are fine, as you try to transition over to the high speed circuits in the carb if the carb opens too soon in relationship to the timing base, (advancing timing) then the engine hits a flat spot and many time dies. The engine runs fine at low speed and fine at high speed. A careful synchronization will in almost every case cure the problem. If you still are having problems you are free to post back and we can work on other things. However I have seen this literally thousands of times. Too much carb for too little timing.
You don't change the timing, just the synchronization.
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