I have a 1980 Johnson Evinrude 115 HP 4 cyl, dual carb that runs well in the driveway with "earmuffs"

Question

However, when in the water, it starts and warms up, even idles for a time, but when under power (forward and reverse), it runs VERY slow and burns gas like crazy. Anyone know what this might be? If it is a carb, how do I tell which one?

Thank you for any help!

Answer 1

hi ;;;;   If it  runs sow as you put it at higher speed then your carbs are blocked...  It could be the float is stuck in the up possition allowing too much fuel through..  It could also be that the high spped jets in the carb are worn and need  to  be looked at.  I would take off both carbs and  clean them both and use carb kits and replace the needles too..

Its a waist of time just doing one carb you might as well do both.

And heres another thing to look at.   You may have changed the spark plugs but you may be getting a situation where your motor isnt firing  on all the cylinders..

Ok  check each plug make sure you have a spark in each cyclinder. My guess would be that when under load one or more of the coils breaks down  becasue its hot  and it expands.....  I had this on my 1973 johnson.   It ran wel idled well but at higher revs when out on the lake it  sputtered  and didnt run well at all..  I changed the spark plugs.. the same happened I cleaned the carbs and it was a little better. I looked at the coils and found one to be cracked..   So I replaced it .... it now runs very well great actually

Answer 2

check to see that it is running on all 4 cyls sounds like it is not that engine will idle perfectly on 3 cyls . when running in the water take off each spark plug wire one at a time(use insulated pliers to prevent shock) and reattach do you notice any power differance? if not that cyl is not running. you can also staticaly check for spark, by hooking each plug wire up to a known good spark plug contacting a ground- then crank engine and check for spark. do this on all four what do you have? as far as the carbs does gas drip out of the front when running? or around the air box?

if you have done the spark test you STILL need to do the cyl drop test as I stated remove one plug wire at a time while running at rpm engine is failing if engine does not change that cyl is not fireing if your at wide open throttle and only 1/3 speed you CAN NOT be running on all 4 cyls since you burn lots of gas than fuel FLOW is not the problem. do the drop test if the cyl fails and you HAVE spark check that cyl for compression/damage. what is the compression? is there water on the s. plug or any other contaminents(aluminum from piston) head gasket?

Answer 3

lgmc is correct and do what he said, also get a timing gun check your spark that way make sure all coils are working also check the spark advance, check with a  book or the dealer i think the spark advance should be about 28 degrees at 5000 rpm..(that's off the top of my head ,so check first), when you do it- put the boat in the water , not on ear muffs. as for the gas consumption , they suck up alot of gas, check for leaks but pther than that they are older and not as efficient as the new ones....i have twin 1984, 185hp and i burn about 25 gals an hour at ful throttle and about 8 to 10 per hour at idle speed...good luck