Outboard motor problem

I have a 1993 50 hp Evinrude that has been sitting in my garage for 4 years un-used. I decided that nonsense has lasted long enough so I decided to see if I could get it running today. I put the muffs on in the driveway and got a fresh tank of gas. It started ok (although it took a little longer than it should.) but it is idling too high. (1500-1700 or so on average)

After a few minutes of idling, the tach starts to act erratic increasing to as much as 2000-2500 and then it makes a popping noise with exhaust blowing out of the prop and the tach drops down to the 1000-1500 area. The tach starts to increase and every few seconds it sputters and the tach drops again. (I think this may be considered a sneeze or cough)

I started and ran it a bunch of times today (in the driveway) and a couple of times it acted different than what I described above. When I would start it, it would idle at around 1000 and then slowly fall downward and die. The next time I would start it, it would then go back to the high rpm and sneeze/cough routine. Strange.

I checked the plugs and they appear to be ok and don't have that much time on them. The ceramic part is a light/medium brown color and they don't have a bunch of crud on them.

I changed the primer bulb and also tried a 2nd gas tank but still got the same results.

I had the carbs rebuilt about 5-6 years ago at a local chain outdoor store and it was running fine 4 years ago when I last used it. (I ran fogger through it when I put it away the last time.) I didn't have any marine grade carb cleaner on hand or I would have tried that today.

I was planning go fishing next weekend but now I am hesitant because I don't want to do any damage to the engine. (I also hate to pull the boat 75 miles only to find it won't run.) I found another site that said the high rpms and coughs could be caused by running too lean which can cause damage.

I don't really want to take it to a mechanic if I don't have to but my time and mechanical ability are both limited. If you have any ideas or suggestions, please let me know.

Thanks for your help.

Dang double post...might as well add something constructive here....fuel filter?

Maybe add a heavy dose of SEAFOAM to your gas/oil mix and run it, then let it sit for awhile (like an hour or more) and run it for a bit again. Repeat this process several times in one day. Let it set over night and start again the next day to see if it starts to run more smooth. If not, you may have other issues. Replace all plugs and check gap settings and all wiries, too, just to make sure.

Disclaimer: Polvo is not a mechanic, so attempt at your own risk.

:hesaid X 2

Fours years is a long time, I would say the carbs are gummed up. Like they said above Seafoam might work but you might have to clean the carbs out.

I tried the Sea Foam, but so far it hasn't seemed to help. I may try a can of engine tuner before looking into tearing down the carbs. I am not extremely mechanically inclined when it comes to engines.

Thanks for the comments guys.

Does the motor rev up and down with the tach readings or is it just the tach that is erratic?

PM sent also.

Were the carbs drained before you put it up last? If not there is a good chance that they need rebuilt. Sitting is the worst thing for an outboard, if its idling to fast it is a fuel problem, maybe a carb out of adjustment or a float is stuck.

Don't forget to have the water pump changed. Should do that every other year.

Thanks guys for the comments.

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dfar
Does the motor rev up and down with the tach readings or is it just the tach that is erratic?

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The motor does rev up with the tach.

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Dlogfish
Were the carbs drained before you put it up last? If not there is a good chance that they need rebuilt. Sitting is the worst thing for an outboard, if its idling to fast it is a fuel problem, maybe a carb out of adjustment or a float is stuck.

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When I winterized it back in the fall of 2011, I treated the fuel with a stabilizer and then ran fogger through it until it choked out and died. I guess I should pull the gas line next time and let it die that way. I've just never let a boat sit that long before without using it. I had a couple of deaths in the family, my elderly mother fell and broke her pelvis, my daughter graduated college, and about a half dozen other reasons I couldn't get out.

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CrappieThumperMK


Don't forget to have the water pump changed. Should do that every other year.

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Yea, I know you are supposed to do that but I always cheat more than I should. I've changed them before that were 5-10 years old and looked brand new when I changed them so who knows.

I think I will spray some marine carb tuner through it before I do anything else but I'm guessing you guys are right that the carbs are plugged.

Thanks again for the help.

Update: I decided to put the boat in the water before doing anything further to the carbs to see if I could "blow out the cob webs". To my surprise, the motor started and ran like normal. I guess the sea foam I put in last weekend did the trick. Perhaps with the sea foam in the line/carbs for a week, it cleaned up what was causing the problem. I don't know but just glad I don't have to tear down the carbs.

Good deal. Now get after those fish

Good news!

We use Marine Stabil in every tank of gas. It has helped our motors a lot.