rustyscrew
Petty Officer 2nd Class
- Joined
- Mar 29, 2006
- Messages
- 141
I just relpaced my old mercury engine with an evinrude 120hp (1988). I had it running pretty well on a stand and now that it is hanging on my transom it is running poorly!
Here are the symptoms:
1) At idle (on the hose) it coughs fairly regularly and almost stalls and then recovers itself. It is like a backfire, a smokey loud cough. Generally it runs pretty rough.
2) At higher speeds (not under load) it still runs rough.
Here are my diagnostic attempts:
1) Compression is 150-155 in all cylinders
2) All cylinders get spark (from spark tester)
3) 3 of the four plugs get a lot of black carbon deposit after only 2 minutes of operation. The fourth comes out slightly wet but not very sooty like the others.
4) Still runs roughly after 2 carb cleaning attempts with Johnson tuner injected into the primer per instructions.
5) Plugs are all new
Clues from the engine:
1) I bought the engine on good faith because it wasn't hooked up to a boat.
2) It appears that it was rained on and stored for some time without the cover on it. (Starter was full of water- required my rebuilding it)
3) It looks as though the previous owner was a tinkerer...I have had to undo some electrical jury-rigging.
4) While working on the engine, I was running 50:1 premix just in case the VRO wasn't working so it was running with a lot of oil for a while.
Theories:
1) gummed up carbs
2) out of tune (could it just need a general tune up?)
3) faulty (corroded) powerpack
Any ideas? I am handy but no expert at this. It would be nice to narrow down the possible problems....any ideas or basic test ideas will be greatly appreciated.
Here are the symptoms:
1) At idle (on the hose) it coughs fairly regularly and almost stalls and then recovers itself. It is like a backfire, a smokey loud cough. Generally it runs pretty rough.
2) At higher speeds (not under load) it still runs rough.
Here are my diagnostic attempts:
1) Compression is 150-155 in all cylinders
2) All cylinders get spark (from spark tester)
3) 3 of the four plugs get a lot of black carbon deposit after only 2 minutes of operation. The fourth comes out slightly wet but not very sooty like the others.
4) Still runs roughly after 2 carb cleaning attempts with Johnson tuner injected into the primer per instructions.
5) Plugs are all new
Clues from the engine:
1) I bought the engine on good faith because it wasn't hooked up to a boat.
2) It appears that it was rained on and stored for some time without the cover on it. (Starter was full of water- required my rebuilding it)
3) It looks as though the previous owner was a tinkerer...I have had to undo some electrical jury-rigging.
4) While working on the engine, I was running 50:1 premix just in case the VRO wasn't working so it was running with a lot of oil for a while.
Theories:
1) gummed up carbs
2) out of tune (could it just need a general tune up?)
3) faulty (corroded) powerpack
Any ideas? I am handy but no expert at this. It would be nice to narrow down the possible problems....any ideas or basic test ideas will be greatly appreciated.
