115 evinrude no top end

[evinrudedad]

I have a 79 Evinrude in 115 hp. Great motor has not given me one bit of problems until this year. I took it out on the pond and it was running full speed not WOT but close so RPM's were not maxed. All of sudden it lost allot of power like I throttled back but I hadn't. I thought it was fouled plugs I replaced them. Took it out again ran fine until I shut it down. Went to go full speed after trolling with my kicker same thing again. It will idle but does not have power past half throttle. Took it out again today wide open it was running great backed it off a little bit and it fell on its face wouldnt plain or nothing. If i run it at full warmup it struggles to. it will max out the rpms on warmup normally now it wont get past 3000. I think my high end jets are plugged but not sure. I tried the fuel tank from my kicker and it had no change. Also when I unhook the fuel lines I hardly see any fuel come out like its not pressured up in the motor. I also took the fuel screen off to see if that was plugged it was very clean. I seen a similar post where someone squeezed there primer bulb at wot to give it more fuel I havent tried that yet. I did find a coil wire that has been cut and spliced back together but it has a good connection not soldered like it should be but pretty good. Any help would be appreciated.

 

[Bosunsmate]

yes try priming the fuel bulb, that works as a manual pump to see if the problems in your pump.
also check that the bulb primes up fast and stays primed with the engine off, that checks for leak in the system
also check spark with a spark tester on all cylinders

 

[emdsapmgr]

Very possible the engine is not firing on all 4 cylinders when you note the running issues. Weak ignition components tend to fail once the engine heats up to normal operating temps. May run fine when cold, the crap out when warmed up, so check the spark on each spark plug when the engine is well warmed up. Constantly priming the fuel hose bulb is a good test to verify the condition of the fuel pump.

 

[evinrudedad]

I'll check the spark gap to make sure it's 7/16 also check the primer bulb as well. I'm leaning towards fuel but not ruling anything out. Not sure if I said it in my post but I have quick disconnects for both my big motor and my kicker so I can use either tank if I need to. Usually when I would put the hose on it would spray a little fuel out that doesn't happen now.

 

[emdsapmgr]

The spark plugs on that engine should be gapped to .030.

 

[Jad88]

I have the same issue, other than it doesnt get full throttle under load at all, i did a compression check and found 124 on one side and 90 on the other, the difference being over 15 lbs, I took off the head on the bad side and the cylinder walls were fine, along with rings are open and checking the head gasket found rust look around a middle bolt which to me indicated head gasket. I would suggesst you do a compression check if your fule tests fail.

 

[Tim Frank]

It sounds like you are saying that when you "warmup" that engine that you give the maximum amount on the little lever....and that it normally goes to full RPM....but now with the current problem it "only gets to 3000 RPM."
I've never in 40 years started and warmed-up an O/B anywhere near that aggressively, and humbly suggest that if you continue exceeding 3000 on a cold engine, with no load, I am confidant that you will be back in here at some point asking whether it is worth doing a full rebuild.

Great motor has not given me one bit of problems until this year

One of the most useful sentences in a post like yours.
New problem, motor has run well for you up to now.Thanks!

I have found that the new gasohols, while not being the evil demons that some portray them as being, do degrade even supposedly alcohol-resistant fuel lines to the point that they break down completely.
At that point, the fuel lines generate a large amount of debris that really compromises carbs and fuel delivery systems.

Check the condition of the "in-motor" lines.
I replace all my small engine fuel lines every 3-4 years.
Went 5 on my lawnmower and was too late.

 

[evinrudedad]

Thanks for the advice on the warm up. I don't usually rev it that high I usually just give it enough on the white lever to keep it running. What I should have said is when it cuts out and runs poorly I put it into neutral to see if I can burn it out some like clean the plugs and such. I'm going to get a timing light today and check all the hoses. Is the carb clean out as simple as I would think? From what I have read the biggest concern is setting the timing with the linkage back to original. If I do attempt this I will probably video the whole process so I can look if I need to. Bright side my little 6 horse kicker runs like a champ and we have been getting in some good fishing. I just worrie about being out where I need speed to get off the water fast.

 

[evinrudedad]

Update finally made time to look at old evin. One of the cylinders had no spark. Swapped the plug wires the cylinder in question came to life and the other one is bad now. I checked all the wiring and grounds they all look good. The coil looks good also but unless that cylinder is dead on the power pack I have a bad coil. Everything else checks out and I am amazed it ran as good as it did on 3 cylinders. I am ordering a new coil as we speak.

 

[emdsapmgr]

You can do a simple test. That engine has dual, identical power packs, one for each head. Swap them. If he "no spark" condition moves to the other head, then the pack is bad. Coils are usually pretty reliable.

 

[evinrudedad]

Update. I ordered the power pack and coil. I figured if one was the culprit and not the other I would have a spare. I put the new power pack on and eureka fired right up and its running on all 4 cylinders with the muffs. Have not tried it on open water yet but I am confident it will run like it used to. And also positive it has new plugs and fuel system treatment in it now as well.