Evinrude 15 1982 Interesting problem

[Mikko]

Starts fine, idle is fine and full throttle is fine whenever I got it to full throttle. It misses for a while when accelerating, but runs well with full throttle. It seems that mid throttle is someway missing. Does anybody have any idea what the reason may be? Carburetor cleaned and floater replaced, same problem before and after cleaning.

 

[flyingscott]

Check spark and compression.

 

[TrueNorthist]

Could be a number of things but procedure usually rules out many issues. Have you done a compression test? Spark test? Timing? And were the carbs given a thorough clean before adding parts? Welch plugs and everything else removed and carefully cleaned, on a clean bench?

Edit: didn't mean to step on your toes Scotty.

 

[flyingscott]

No timing on those just a link and sync.

 

[racerone]

Hook up a timing light to the top cylinder.-----Out on the lake take the boat to full speed.----Observe spark behavior on the light.------Slow down and repeat with bottom cylinder.-----Post what you observe.

 

[Bosunsmate]

Check your wiring too, sometimes they are worn where they rub under the flywheel as the timing base turns

 

[Mikko]

Thanks for the advice. I do not have any special devices to make tests, but I can check the easiest ones. It shoots also a bit while revving at neutral.

 

[Bosunsmate]

People often find a tiny bit in some of the small orifices in a carb that was missed the first time through. I always put a soft copper wire the whole way through mine

 

[oldboat1]

The high speed orifice on your motor is in the center of the carb, up in the middle. I would pull off the carb once more and make sure that jet is squeaky clean (soft wire and some carb spray using the plastic nozzle that comes with the can.) Also, one of the tests for cleaning and adjustment of the low speed circuit on top is a throttling up test. At worst, the motor will stall, but if partially blocked or not properly adjusted (usually too rich), the engine will stutter when throttling up.

Your best solution might be to disassemble the carb and soak both halves in lacquer thinner, then clean out all openings and passages as above.

 

[TrueNorthist]

Cleaning carbs is incredibly finicky. Just a pin-point of something can wreck hours of work. Last thing I do through reassembly is spray carb cleaner from a can as I go. Even then sometimes something sneaks through. It takes just a spec of dust to mess up a well used carb body.

If I'm not mistaken, the carb you have is three stage: low, mid and high rev circuits. All must be spotless.

 

[oldboat1]

http://ww2.iboats.com/Carburetor-Ma...753489--session_id.253020087--view_id.1547067

Look for an idle speed mixture screw on top, and a h.s. jet down at the bowl. Take off the expansion plug on top (domed shape plug) to access idle passages. Disassemble and soak top and bottom, leaving linkages in place.

 

[Mikko]

My carb was cleaned with ultrasonic cleaner (not by me) and I was fairly confirmed that it should be fine. I can test an other carb as I have two 15 Evinrudes (1980 and 1982).

 

[TrueNorthist]

Your situation may differ, but I ditched a commercial ultrasonic cleaner (800watt, 10 litre) due to it failing to adequately clean fine interior circuits on larger carbs. Sometimes it worked fairly well, others it merely superficially made it look clean. Again, I'm not saying yours was not properly cleaned, just that I found them ineffective far too often. I decided there is no substitute for getting hands on when ensuring fully clean carbs. Even then sometimes I have to repeat the process. It just happens.

And another used carb might prove a quick but still somewhat inconclusive solution. Might also introduce further complications. OB1 again offers good advice above and I'm inclined to agree.

Sorry to be so seemingly unhelpful, but Murphy lives in my shop most days and I've learned to be ultra fussy about procedure. Might not be carb at all, but repair by forum is tricky at best.

 

[Mikko]

I have not done these carb things by myself (except removal and reinstall), but I'd like to follow OB1's instructions. However, I did not fully catch which part is which (in exploded view). Once I took the entire power head out when changing the gaskets/seals in water circuit (in top of the copper tube) by following leeroysramblings.

 

[oldboat1]

Buy an oem carb kit. Take off the air horn on the front (start with vertical screws holding top to bottom). Remove carburetor from engine. Detach bowl from top of carb, again removing screws facing up). Remove the cam follower, but leave the other linkages in place. Remove idle needle. Remove float and float valve (26). Soak top and bottom of carb in lacquer thinner.

 

[Mikko]

I change the carb from another 15 Evinrude and the problem is exactly same. I am sure it is not the carburetor. It idles fine but in the tank, idle gets rough when trottling up. It seems that there is exhaust gas coming out somewhere in the powerhead to exhaust housing area. Could it be some leak in the exhaust system? I checked the sync and link and the timing mark touches the trottle lever at the right point.

 

[racerone]

Fact-----Carburetor " problems "---Usually turn out to be something else.

 

[TrueNorthist]

I think the rules of the universe state that every "problem" turns out to have a different solution than the one chosen. It's likely why I went grey at 20 years old.

 

[raczekp1]

sucking air at some joins can be the problem