1980 Evinrude 50 HP Help

[Justducky2]

I'm in the process of trying to get my new to me 1980 Evinrude 50 hp 2 stroke to run right. Here's what I know and did so far:
Compression test 145 top cyl, 140 bottom cyl. New plugs, New non ethenol gas, proper 2 stroke oil mix, cleaned the carbs out still on the engine with carb cleaner and sea foam, New coils and plug wires, new voltage regulator. (the battery wasn't being charged with increased RPM) It starts and runs on the muffs but doesn't rev up very high, maybe 3000 rpm is my guess and when it does rev up is "misses" in a irregular pattern like it's not getting a spark all the time. It shifts into forward and reverse good and revs up with the same misses on the muffs. I thought it might be the old coils so thats why I put new ones on.

So I put it in the water at the ramp to test under load and it stalled several times when putting into gear so we didn't go anywhere that day.. the engine seemed to struggle to get to a lower rpm than before with the fast idle lever up. When I pulled the plugs afterward, the top plug looked good and the bottom plug had a trace of oil on it. I've had motorcycle engines apart and fixed them but they were 4 cycle. So given these symptoms What should I do next to diagnose and fix the problem? I'm not afraid of working on this engine myself, just don't know what to look at next. Thanks in advance. Brad

 

[oldboat1]

Buy carb kits, pull off the carbs and give them a proper cleaning. Replace the impeller. Test run at low to moderate rpm in a large test barrel, or in the lake -- not on muffs.

 

[flyingscott]

Stop revving it on muffs or you will have bigger problems! The miss when overreving it on muffs is normal and not a good thing. Have you checked for spark? You cannot properly clean any carb 2 or 4 stroke without taking it apart and soaking it.

 

[Justducky2]

I did not know about high rpm on the muffs. OK so next step will be to order a rebuild kit and rebuild the carbs. I've done that on motorcycles so it should be similar. The linkage looks complicated so I will take lots of pictures and notes before I pull them off.

 

[Bosunsmate]

check your timing base is moving, these can stick or the ball linkage pop out

 

[Justducky2]

I don't know what a timing base is. What does it look like and where is it on the engine?

 

[Justducky2]

OK I found the timing base. Pardon my ignorance. Yes the linkage is good and it moves with throttle. I will check the connections on the harness from the timing base for corrosion. Is there an ohm meter value across the terminals that it should be? Also I pulled the carbs off and took them apart and cleaned them yesterday. Much easier than I thought it would be. Now just waiting for the rebuild kit to arrive.

 

[Bosunsmate]

cdielectronics.com has all that.

but checking they dont have connection to earth is a start

 

[Justducky2]

UPDATE: I Got the carb rebuild kit today and rebuilt the carbs and put them back on the motor. While I was waiting for the kits last week I got a rain barrel and cut off the top to make a test tank. The engine runs good now in the test tank, shifts into fwd and reverse without stalling and seems to run much better now. Last week I also tested the timer base ohms and they were within spec so it must have been the carbs, Thanks everyone for the advice. The real test will be in the water at the launch ramp next time I go out.

 

[boobie]

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