1977 evinrude 115hp problem need help

[dooge09]

Hey guys, I am new to this forum and whole site actually. I thought that maybe if i could get some feedback from other boaters it would save me a very pricey trip to the shop. ok, so very recently my 1977 115hp evinrude V4 has been running very funny, it will run and idle, sometimes good, sometimes kind of rough. when it idles nice it will idle good for a bit, then sort of cough (can see blue puff out the back) you can literally hear the rpms drop, then it will die shortly after. start it up, and then it might do it again in 2 minutes, 10 minutes. or it wont do it at all. so, then when i run it same thing, sometimes it runs awesome, but not for long. at max speed it will pulse, like a cylinder cuts out or it doesnt get proper fuel, rpms and speed goes up and down, sometimes it runs so rough it wont pick up much rpms at all, and wont even plane the boat. i figured it may be the coils, i noticed 2 were newer already, so i replaced the older ones. nothing same problem. so then i replaced the fuel pump thinking it may have been week, still nothing. new spark plugs as well. If anybody can help me, it would be greatly appreciated! thanks guys...

 

[emdsapmgr]

Re: 1977 evinrude 115hp problem need help

You may have an engine ignition component which is failing. That specific ignition component will usually fail when the engine heats up to normal operating temps. (It may run just fine when before it warms up.) When you think the engine is not running well, check for spark on each plugwire. You may find one plug is not always firing. An inductive timing light will help you with this test. Usually spark plug coils are pretty reliable, so concentrate on qualifying the stator, power pack and timer base. Some technical assistance is always helpful here, so check out the troubleshooting information at: cdielectroics.com

 

[dooge09]

Re: 1977 evinrude 115hp problem need help

Yes I thought it maybe be one of those 3, but if the stator was failing wouldn't it generate no apart to any of the cylinders? And a power pack would effect 2 cylinders right? As there is one per side. Where do I find the timer base?

 

[emdsapmgr]

Re: 1977 evinrude 115hp problem need help

Stators can start to fail by not sparking all 4 cyls each revolution. It may spark all 4, it may spark only 3. You need to double check the year of your engine if you have two power packs. The 77 model only has one. The double power packs started with the 1978 year. What is the model number off the tag on the transom bracket? The timer base sits under the flywheel, inside the stator.

 

[dooge09]

Re: 1977 evinrude 115hp problem need help

Hmm I am pretty sure I have 2 power packs, they are the black module looking things mounted on the side a little further back closer to the plugs right? If so, then I have one on each side. How do I begin to diagnose which component is failing?

 

[jessp]

Re: 1977 evinrude 115hp problem need help

Just had my timing replaced and it
Runs better than it has since I've owned it. Also had a small piece of silicone drop into carb n choking off fuel. Seems it was only firing on 3 cylinders. Firing great now. Couldn't be more happy. Mine is an '82

 

[Solittle]

Re: 1977 evinrude 115hp problem need help

Hmm I am pretty sure I have 2 power packs, they are the black module looking things mounted on the side a little further back closer to the plugs right? If so, then I have one on each side. How do I begin to diagnose which component is failing?

You need to troubleshoot rather than guessing. Start by checking compression then spark. Use the Search if you need to know how to do these.

Based on your description I would carefully check the fuel lines and connectors for the possibility of air leaks.

 

[wilson doug c]

Re: 1977 evinrude 115hp problem need help

I have a 76 rude 115h mine was doing similar try cleaning the found to the per pack and coils it fixed mine hope it works

 

[emdsapmgr]

Re: 1977 evinrude 115hp problem need help

If you have diagnosed which cylinders may not be firing, you can swap the power packs. One controls the spark to each head. See if the firing problem moves to the other head.

 

[dooge09]

Re: 1977 evinrude 115hp problem need help

Awesome thanks! I think I will check my fuel lines, I noticed yesterday there are 2 holes in the front of my fair box one middle one lower, missing bolts? Maybe causing a vacuum problem? Also gasket was destroyed not doing anything. As for which cylinder, I do not know which ones aren't firing. I'll run it up in the yard n try to see.

 

[emdsapmgr]

Re: 1977 evinrude 115hp problem need help

You can test for spark on the spark plug wires (when cranking) by using a drop cyl test or hook up an inductive timing light to each wire. The flashes from the gun will show the quality of spark.

 

[dooge09]

Re: 1977 evinrude 115hp problem need help

ok, i will get and inductive timing light and give it a shot. did compression test, not sure how the order of cylinders goes but 3 were at 90-95 and one at 68. im guessing thats a problem.

 

[emdsapmgr]

Re: 1977 evinrude 115hp problem need help

Normal engines have compression which is within 10% of the other cylinders. Your 68 cylinder is very low. You may be lucky if it's just a blown head gasket. Pull the head and have a look at the seal ring on the gasket.