40 hp Evinrude misses over 2000 rpm

[marchandjohn]

I have a 1992 40 Hp Evinrude that starts shaking terribly and missing above 2000 RPM. This started while I was on vacation. It was running fine and then started missing and bucking, the low oil alarm also started beeping. I brought it to the local Evinrude dealer, he put in new plugs, Champion QL78YC, changed the water pump and the temperature sensor. It ran for about 20 Min. and started doing the same thing. Dealer changed the VRO the next day. It ran fine for an Hour and did the same thing. Dealer then changed oil cap and ball. Ran for a ½ Hour and did the same thing. I bought a manual and disconnected the VRO at the 4 wire harness and ran on a tank of 50:1 premix, same problem. I think it might be the voltage regulator or Tach- Feedback, although the Tach is working. If so do I need the meter in the manual or will a good Fluke work. Thanks John

[ob]

When the problem first arose had the boat been sitting out of use for a spell?That dealer sold you everything but the kitchen sink.Did he eliminate fouled carburetors?Was the alarm you had initially rapid sort tones or one short tone every 40 secs?Just trying to insure what you were hearing was in fact the low oil alarm and not the no oil alarm.

[marchandjohn]

short rapid tones while boat was running then i shut down the 40 hp engine, boat sat for entire winter. Thank you, John

[ob]

Short rapid tones indicate a no oil alarm.Have compression tested to insure no cylinder wall damage has occurred.Both cylinders should read over 100 and within 10%.If compression reading is good I would suspect that you have a restriction in carburetor fixed orifices or porting.Quite common in two stroke outboards that have set out of use for a spell.If you intend to restore the engine to its original VRO oiling you need to insure that the oil reservoir and its pickup tube are clean and clear of any obstructions and is reprimed before using.When putting the VRO back into service after it has been replaced or maintenanced it is recomnmended to run premix at 100/1 until oil use from reservoir can be established.This can be done by marking a line on the side of the reservoir and noting when the level has dropped.

[marchandjohn]

ob Thank you,i'm going to try cleaning carbs now. get back to you with results.Thanks, John

[ob]

marchandjohn,Pay particular attention to the bowl pickup tubes for gummy restrictions.