1978 Evinrude 115, Need some expert help.

Hello everyone, my name is Jonathan (John for short)
I've followed this site for a few months now and learned a lot and just decided to recently sign up, so kudos to everyone for all their great advice and knowledge as you've been a key part to my success with this motor.

Here it goes, in Feb this year I recently purchased a Larson Shark 18ft tri hull (forgot year, roughly around same as engine.)
and have been using it as my weekend/spare time project between surgeries and etc. Originally it had twin 40's I was told and one popped so the guy bought a 78 Evinrude 115 in non running condition, was told it needed carbs sync'd & linked and it's good to go...

Well here's june and I've flushed and refilled the gearcase, new seals all around for the lower unit with a new water pump, new spark plugs and being an ASE technician on automotives and being an auto enthusiast since pre-teen I checked the carbs and found them to be in great condition no tarnishing or bad seals, floats work good and all gaskets are tip top.

I've used fresh fuel and Pennzoil 50:1 mixing directions and I have come to some serious problems so far...
I took her out on the water and just could NOT get her above maybe 15-20MPH no matter what, she doesn't overheat but after maybe half-ish throttle she just doesn't go, it seems to slightly bog down... And she smokes, like a lot...
So looking further into it I notice on muffs ANYTHING above base idle and she pops and stutters and shakes...

So, I bust out my spark checker and ALL the packs fire GREAT, very bright blue strong spark and no intermittent sparking.

So I think wtf... Compression test, well I was very surprised and somewhat astonished... All cylinders have only 65PSI.
So I do one more test to see if maybe when the ignition components get warm they foul, so with the engine on muffs at idle I start pulling plug wires, starting on the left side of the engine (looking at them from the back standing in front of prop) each plug pulled on left side almost instantly nearly killed the engine until put back on.

Right side, absolutely no difference in idle at all, no different exhaust note, NOTHING AT ALL... I'm like wtf I just tested the spark! So I grab my spark tester, and both plugs are still firing perfectly. I took both plugs off the right side of engine and nothing happened, no idle change, no different exhaust note, nothing...

Now I know 65PSI is seriously freaking low, like how the hell is it still working low... But I'm trying to put off the whole head work until after summer because we wanna do some fishing and cruising on the water. I don't need to do 60MPH or anything but 15 was just almost not bearable...

My question is why is the WHOLE RIGHT SIDE not firing?! Head gasket? Piston rings? I looked all around the gasket and noticed no seeping of fuel or oil and no damp spots at all, all dry and all still the same silver paint color of the engine telling me the gaskets are hella old... So what could cause that? I'm beyond stumped, I have the same cylinder pressure as the left side of the engine, same spark, and the cylinders absolutely get fuel because it spat at my face when I turned it over... What am I missing?

Re: 1978 Evinrude 115, Need some expert help.

I've spent quite a bit of time up to the arm pits in a few of these motors recently and would say there's a couple of things you can quickly check to see what's going on.

Compression:
If you pull the exhaust jackets (bypass covers-part 19 on most parts diagrams) from the sides of the the block (2 squarish about 2 1/2" each) you'll be able see the cylinders. If you remove one you might as well check all four since that's how the gaskets are sold. Look for the obvious badness there- scoring, discoloration, the usual. Heads up, you'll have to replace the gaskets before running the motor again but it could give you a clear indication of what's going on before spending any more money.

I should note: FIRST, you can pull the heads without replacing the gaskets since they are the "no glue" type. Here you can do a no fault/no charge visual to inspect the rings as well as gasket inspection. Be sure to not remove cylinder head cover on the outside of the head unless you have a day set aside for gasket removal. That part is part of the cooling system. As a car guy you'll know what doesn't look right.

Spray the heads down with soapy water and visually look for air leaks to see if something sticks out.

Dead Side:
What happens when you spray gas/oil mix into the carb with the throat open? Obviously if it revs right up you'll be able look at fuel delivery as one of the potential problems. The top and bottom carb are the same (on the '77 at least) so what happens when you switch them - does the other side fire then? I had one carb that I finally realized was never going to work no matter what I did to it.

Eliminating/Confirming any of these would get you closer to the source of the problem(s). These motors are really good, tough, and most of all really simple with the potential to be extraordinarily maddening. I have a '77 85hp powerhead in my garage right now I need to mate with the body and gearcase from an exploded 115 I got for $100 (the entire cooling system was full of salt) that I used as a donor for the ignition parts. One day to build, one week to chase out the gremlins.

Re: 1978 Evinrude 115, Need some expert help.

nphilbro said:

I've spent quite a bit of time up to the arm pits in a few of these motors recently and would say there's a couple of things you can quickly check to see what's going on.

Compression:
If you pull the exhaust jackets (bypass covers-part 19 on most parts diagrams) from the sides of the the block (2 squarish about 2 1/2" each) you'll be able see the cylinders. If you remove one you might as well check all four since that's how the gaskets are sold. Look for the obvious badness there- scoring, discoloration, the usual. Heads up, you'll have to replace the gaskets before running the motor again but it could give you a clear indication of what's going on before spending any more money.

I should note: FIRST, you can pull the heads without replacing the gaskets since they are the "no glue" type. Here you can do a no fault/no charge visual to inspect the rings as well as gasket inspection. Be sure to not remove cylinder head cover on the outside of the head unless you have a day set aside for gasket removal. That part is part of the cooling system. As a car guy you'll know what doesn't look right.

Spray the heads down with soapy water and visually look for air leaks to see if something sticks out.

Dead Side:
What happens when you spray gas/oil mix into the carb with the throat open? Obviously if it revs right up you'll be able look at fuel delivery as one of the potential problems. The top and bottom carb are the same (on the '77 at least) so what happens when you switch them - does the other side fire then? I had one carb that I finally realized was never going to work no matter what I did to it.

Eliminating/Confirming any of these would get you closer to the source of the problem(s). These motors are really good, tough, and most of all really simple with the potential to be extraordinarily maddening. I have a '77 85hp powerhead in my garage right now I need to mate with the body and gearcase from an exploded 115 I got for $100 (the entire cooling system was full of salt) that I used as a donor for the ignition parts. One day to build, one week to chase out the gremlins.

Click to expand...

I will probably just pull the heads to do the inspections but I'm a firm believer in if you pull it, replace it, better off in the long run in case it has a score somewhere or weak and causes compression loss. I've found them to be ridiculously cheap, (I think like $12 each for the Sierra ones.)

And honestly I can open the throttle plates when idling and watch the jets spray perfectly down the throats and all it does is idle up and shake/pop/crackle and throws out a EPA violating amount of white smoke. I tested that theory with the plug wires on and off and it made no difference when "punching" the throttle.

The plugs on the right side do get pretty soaked and I can tell it's just spitting the fuel mix out the exhaust because the prop and grass behind it are soot black and oily/fuel smelling.

And I totally agree this motor is able to take some serious punishment, it ran on the river for a good 2 hours on two cylinders and never over heated or gave out and then when flushing with tap water at home it started right up (well kind of, on two cylinders she likes to be a pain in the....)

Re: 1978 Evinrude 115, Need some expert help.

Oh I have one more question to add, maybe it could be the answer...

On this motor I'm assuming I have overheat sensors on the heads because on each head I have one orange wire that comes out of the head cover and leads somewhere into the harness... Is it possible for that sensor to cause a no fire on one side? I haven't tested this because I'd assume it would cut spark and I have great spark.

Thanks for any help!

Re: 1978 Evinrude 115, Need some expert help.

My opinion:
You don't have spark on the bank that's dead. Have you checked the spark with an air gap tester? If compression is the same on cylinders and 2 are running on one side, and the other side with the same compression are not, it's either fuel or spark. Since you've verified spark and fuel from the carbs, the only other thing it could be is that the dead bank has some stuck reeds which are preventing crankcase pressure from building up high enough to push the fuel into the cylinders. Since you say the plugs are getting pretty soaked, and that you've seen fuel going through the carb throats, the only conclusion that I come to is that most likely you tested spark by grounding them on the block and not with a spark tester to see if it will cross a large enough gap to fire under compression.
Anyway, that's just my guess. I hope it's helpful.
BTW, you're a heckuva lot better mechanic than me if you're ASE certified, so take my answer with a grain of salt. I just wanted to mention that your motor probably has o.k. compression because when they're bad, they're rarely even ,and because some of those old OMC's were low compression engines to start off with. I'm not sure about yours because I rarely work on motors with more than 3 cylinders. I'd almost guarantee that something is causing no spark on your bad bank, though.
GOod luck,
JBJ

Re: 1978 Evinrude 115, Need some expert help.

jbjennings said:

My opinion:
You don't have spark on the bank that's dead. Have you checked the spark with an air gap tester? If compression is the same on cylinders and 2 are running on one side, and the other side with the same compression are not, it's either fuel or spark. Since you've verified spark and fuel from the carbs, the only other thing it could be is that the dead bank has some stuck reeds which are preventing crankcase pressure from building up high enough to push the fuel into the cylinders. Since you say the plugs are getting pretty soaked, and that you've seen fuel going through the carb throats, the only conclusion that I come to is that most likely you tested spark by grounding them on the block and not with a spark tester to see if it will cross a large enough gap to fire under compression.
Anyway, that's just my guess. I hope it's helpful.
GOod luck,
JBJ

Click to expand...

I'm not fluent as to what an air gap tester is... I have a tester that the boot plugs into that acts as a spark plug and yes it grounds onto the block. The arc of the spark though has to travel about a half inch before it grounds to the metal sheath surrounding the electrode. I'd assume that's plenty far as the gap of our plugs is only .30...

How can I check and or test the reeds to see if they're faulty?

P.S. Thank you all so much for the quick replies, you guys are awesome!

[Added]: Sir, I appreciate the compliment but I only offer that up so others can assume I am somewhat mechanically inclined.

I in no way will ever put my education above tried and tested busted knuckle garage knowledge which is the true knowledge around an engine or subject, and I know that most of you have bust a few knuckles and spat a few curses towards your engines making them run the way they do now

Re: 1978 Evinrude 115, Need some expert help.

If it's crossing a 1/2" gap, it should be fine! I wonder if you have gotten unlucky enough to have switched the plug wires, or have 2 bad plugs? That's the only thing I can think of....
The reed blocks are under the back side of the intake manifold, behind the carbs. You could remove the carbs and take a peek through the intake ports. However, I suggest that you don't do it because they're very rarely a problem and because the plugs are wet, indicating fuel is getting there. I guess you could ground the plugs on the good bank, and spray some premix into the bad bank's spark plug holes and put the plugs back in and see if it fires up momentarily. If so, that would be a really good indication of stuck reeds. I just really doubt that's the problem, and that it is a spark issue somehow. I'd think it'd be hard to switch those wires, but worth looking at.
iJBJ

Re: 1978 Evinrude 115, Need some expert help.

I'm unsure if this is allowed here, if so inform me as I do not wish to violate any message board rules or regs, just wanting to pass information about my testing tools. This is the tester I use located here, and I am in no way promoting their tools or represent them in any manner. http://www.matcotools.com/catalog/product/KD2757/STANDARD-IGNITION-TESTER/

And I don't know?... I'd have to take a picture for you tomorrow, I know my blue power packs have a lead out that connects by a two pin connector that then splits to two coil packs, honestly I did not think at all to reverse the plug boots... I will have to try that tomorrow and see what outcome I get. I will feel so ignorant, lol. But they're not labeled nor do they differ in any way, the wires are all the same length on the packs so it's kind of a guessing game I guess.

Thanks for bringing that to light, makes me wonder! (See, busted knuckle garage right there )

Re: 1978 Evinrude 115, Need some expert help.

The spark tester that I use is about $6 at autozone, and has an adjustable air gap. Yours is probably fine. I like to adjust the air gap to about 1/4 to 7/16" to see how much of a gap the spark will cross with a hot blue pop every time. If it only crosses about 1/4" and the spark is weak and orange looking, it's not enough.
Either way, I'm really suspicious that your spark plug wires are crossed, or that the wires coming from your powerpack to the the coils are crossed. Either situation would cause your spark to be timed opposite.
I hope it's that simple!
Good luck, and I'm eager to hear the outcome...
JBJ

Re: 1978 Evinrude 115, Need some expert help.

It's funny, but a faulty reed valve was the first thing that came to my mind but I've never seen one go bad in these motors (not to say they don't) but if I recall correctly they feed in conjunction with the carb - top or bottom but not left or right.
Plug config is simple enough, outside coils to bottom plug.

My guess is there will be much more revealed when you open the head and pull the side covers. There could very well be a lot of carbon buildup you were burning out so you might want to verify the thermostat is present and working while you're in there. I was just trying to map out discovery starting from the easiest and inexpensive.

Re: 1978 Evinrude 115, Need some expert help.

FYI... here's a pic from CL on a '72. This should exclude the reeds.

Re: 1978 Evinrude 115, Need some expert help.

Ok well simple worked, the damned plugs were backwards! Took her out today and man oh man does she haul! I think it's lean though cause pulling a wake boarder or not I can only hit about 4700 RPM. And she liked to stall a lot, every 45 minutes or so at low idle it'd sputter and die and I'd have to choke it to crank. But otherwise she did great and I think a few turns of the carbs to richer and it'll run great.

Re: 1978 Evinrude 115, Need some expert help.

I'm glad to hear it ran well for you! I guess we forgot to mention the ceramic part of the plug goes on the outside of the block.

These old engines are hard to beat. So what's the deal with the compression??? Was it a faulty reading? There's no fuel adjustment on these carbs outside of rejetting. Since you are getting it to run you have the perfect opportunity to treat it with seafoam to clean the whole thing out.

If you're getting good compression on all four you'll want to look at propping it correctly for what you use it for most. It's sounds like the performance was outstanding with that kind of load. Prop calcs only need GPS top speed at WOT, RPMs, and Pitch and you'll have an idea of what the prop is up to.

Re: 1978 Evinrude 115, Need some expert help.

Lol allow me to rephrase that the wires from the coil packs were backwards. And the motor seems pretty strong but I think I'm lean at idle because it wanted to die a lot and I have her idled in water at about 950 to stay idled but shifts perfectly smooth. Sometimes when punching it from a stop it would choke up and then catch back up and just haul arse. I think for sure the blade pitch is wrong because it's a three blade and looks old as hell and pretty beat up, but no matter what about 4700-4900 was my top rpm. I need to operate her about 5500 but I have no idea the current pitch to start my buying from. The motor calls for a 17 but I wonder if that's too big for a tri hull with a 20 gallon tank plus huge cooler and 5+ people. I want to try a 15 and see if that's good. And compression hasn't changed but the motor runs outstanding how it is. I just know I'm too lean because my idle air mixes are only a half turn from seated.