1979 115hp evinrude not taking full throttle

dudebuddy · Jun 30, 2013

I have a 1979 115hp evinrude with power rilt and trim. The motor idles and cranks perfect but when I open it up it only seems to go half throttle. I took boat to lake and noticed the problem so I went home and took off carbs and cleaned then with carb cleaner and also checked gap on plugs. even after all that no improvement. so I changed all fuel lines and cleaned screen on pump still no improvement. I have rebuilt car engines all my life but im stumped on this . Any ideas on what to do next I can use the help thanks

Bosunsmate · Jun 30, 2013

Re: 1979 115hp evinrude not taking full throttle

I just rebuilt a 1982 90 that was acting the same.
Check spark on all cylinders and compression.
The one i worked on had no spark on one cylinder and broken rings on all others and 0 compression on cyl 4 yet still went to half throttle

dudebuddy · Jun 30, 2013

Re: 1979 115hp evinrude not taking full throttle

Bosunsmate said:
I just rebuilt a 1982 90 that was acting the same.
Check spark on all cylinders and compression.
The one i worked on had no spark on one cylinder and broken rings on all others and 0 compression on cyl 4 yet still went to half throttle

I have checked compression on all cylinders, all cylinders are 120. I have spark on all 4 cylinders. Are there any other suggestions to what else could be causing this problem.

classiccat · Jun 30, 2013

Re: 1979 115hp evinrude not taking full throttle

have you verified that the throttle butterflies are completely open at full throttle?

dudebuddy · Jun 30, 2013

Re: 1979 115hp evinrude not taking full throttle

BlueFin16 said:
have you verified that the throttle butterflies are completely open at full throttle?

they seem to be opening up all the way. Also one more question I have the original manual for boat it says that the plugs should be champion L77J4 with a .040 gap but the plugs I got are champion L77JC4 could the gap be different for these plugs (after 30 years I guess things could change)

fireman57 · Jun 30, 2013

Re: 1979 115hp evinrude not taking full throttle

The gap will be the same, either .030 or .040 whichever you are comfortable with. I am betting that your engine rpms go up but your speed does not increase. Might have a spun hub on your prop.

dudebuddy · Jun 30, 2013

Re: 1979 115hp evinrude not taking full throttle

the rpm don't go up they go down it feels like when a holley loads up on a 350 chevy. The carbs have fixed jets so how could this be possible but like I said earlier im a car mechanic not boats. the motor seems to have new gaskets like it has been redone at some point but I cant really say. could maybe the timing be out some or maybe may it be a weak fuel pump. or maybe could a coil be misfiring when it gets hot

fireman57 · Jul 1, 2013

Re: 1979 115hp evinrude not taking full throttle

Did you run a very small piece of wire through each jet, hole in the pickup tube, etc...? just spraying cleaner through them doesn't always do it. The high speed jet is behind the drain plug. Make sure it is clean.

Joe Reeves · Jul 1, 2013

Re: 1979 115hp evinrude not taking full throttle

Clean the 4 high speed jets with a piece of single strand steel wire.... solvent just doesn't do a proper job of it.

Butterflies "seem" to open all the way? At full throttle, they should be perfectly horizontal (wide open). Are they?

dudebuddy · Jul 1, 2013

Re: 1979 115hp evinrude not taking full throttle

butterflies are opening up all the way I rechecked them I will take carbs back off and try the wire through the jets. I will let you know how that does. And again thanks everyone for the help

Bosunsmate · Jul 1, 2013

Re: 1979 115hp evinrude not taking full throttle

Check your timing too.
A car mechanics motor i worked on didnt do the flywheel nut to torque and so the woodruff key broke and the timing changed but since it only slipped at high speed the flywheel still looked as fine to him as when he put it on.

classiccat · Jul 1, 2013

Re: 1979 115hp evinrude not taking full throttle

^^^ +1

here's a check your spark advance before you get to the water: Joe Reeves WOT timing procedure.

TD_Maker · Jul 1, 2013

Re: 1979 115hp evinrude not taking full throttle

I have a suggestion for you...its going to sound stupid, but you need to check it out. The hood latches on the old V-4's tended to grab the little brown coil connections and pull them loose from the connectors. Just two little pins inside of those connectors. The old V-4 115 drove me crazy (with dropping cylinders) until I realized what happened.

Eyeballsdeep · Jul 2, 2013

Re: 1979 115hp evinrude not taking full throttle

Hey I never thought of that! I have a 76- 84 can't remember what year, but it always had an intermittent spark problem. It would idle fine but once you get up it would just bog down then run on 2. I should do a comp test to see where it's at. Good thing I read this thread. It was a good motor but always fouled plugs and I did clean the carbs. Seemed they looked ok. I didn't check the flywheel key yet. I might have to take that off anyway to get to the stator incase it's bunged or it could be anything realy. I just don't want to spend a whole lot of money on this thing.

kenmyfam · Jul 2, 2013

Re: 1979 115hp evinrude not taking full throttle

How did you check for spark ???

dudebuddy · Jul 2, 2013

Re: 1979 115hp evinrude not taking full throttle

I pulled the plugs out and hooked up the wires (with plugs out) and turned over the motor all plugs seem to have good fire in them are there another I can check them

classiccat · Jul 3, 2013

Re: 1979 115hp evinrude not taking full throttle

dudebuddy said:
I pulled the plugs out and hooked up the wires (with plugs out) and turned over the motor all plugs seem to have good fire in them are there another I can check them

testing the plugs outside of the motor isn't enough. Try using an adjustable spark tester. It should consistently pop across a 7/16" gap with a strong blue spark.

Joe Reeves · Jul 3, 2013

Re: 1979 115hp evinrude not taking full throttle

(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4

rothfm · Jul 3, 2013

Re: 1979 115hp evinrude not taking full throttle

Had this symptom on 1993 Johnson 115 at start of my season (new to me). It was Link/Sync and timing advance related. I Also thought the carbs were opening up initially, but in fact were not. I followed the Revees procedure along with some other info here.....and got it from 4000rpm to 5400 RPM and runs great in all ranges now.

Of course before that i did spark, compression, fuel and lots of other checks. That procedure fixed me up.

kenmyfam · Jul 3, 2013

Re: 1979 115hp evinrude not taking full throttle

BlueFin16 said:
testing the plugs outside of the motor isn't enough. Try using an adjustable spark tester. It should consistently pop across a 7/16" gap with a strong blue spark.

Well responded and said.
Joe Reeves method and comments are the voice of experience as well. You have some great information and advice. Use it wisely.

1979 115hp evinrude not taking full throttle

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