87 Evinrude engine surge on 3 cyl

[Ray Ikenberry]

Problem started when running

Problem started when running fuel out of carbs at end of one trip to lake. I disconnected the fuel line and the motor was running good up to last of the gas in the carbs and 1 cyl cut out before the other 2 ran out of gas. Motor ran another 20 or 30 sec on 2 cyl. The next time to lake motor ran good at low speed but started to surge when I increased to fast water speed. It felt like it was intermittantly missing on one cyl. Then it quit surging and I couldn't get it to go fast at all. It still felt like it was running on 2 of the 3 cyl. I had to return to the dock at 1/3 speed. I am thinking the carb on 1 cyl is not working properly. Any ideas on this? Ray

 

[joereeves]

"Ray.... Regardless of what th

"Ray.... Regardless of what the problem might be, always start out by checking the compression and spark. The compression should be 100+ psi and even on all cylinders. The spark (with the s/plugs removed) should jump a 7/16" gap on all cylinders. If those two aspects of the engine are okay, I would strongly suspect a carburetor problem.

NOTE... It's not a good idea to run any engine out of fuel that has more than one carburetor. The top carburetor will run dry first, and this leaves the engine running on the other carbs. The result is that you will have at least one "Aluminum" piston running up and down a "Steel" cylinder wall with no lubrication. Really not a good idea!

Joe

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[Ed Balentine]

" Have '76 70 hp johnson.

" Have '76 70 hp johnson. Was told by dealer in 1981 the idle jets were supposed to be drilled for altitude[3000 ft] anyone heard about this? If so, what size to drill? The engine has flat spot at high idle like when powering onto trailer. Paid to have this done,but still have same problem. "