1978 15hp Evinrude won't open up

[wingsaircharter]

My son just bought a 1978 15 hp Evinrude for a 14 foot fishing boat. The guy started it on a saw horse with muffs and it sounded ok other than would quit at low idle. We got it home, put it on the boat, and started it up. I adjusted the idle speed on the side and the idle mixture and it seemed ok. It seemed to run out ok, but not knowing what a 15 would do on a 14 foot boat, I really didn't know what to expect but it was probably doing about 10mph. Kind of seemed like it might be running on one cylinder. After running it a while, all of a sudden it opened up and seemed to get about double the power. It was intermittent and then went back to what it was doing. That is the reason that I now know that it isn't right. Changed plugs. The bottom one was kind of wet compared to the dry top one. New plugs didn't help. I ran the engine at idle with each plug wire removed and it would run on either cylinder so it seems both have spark which is leading me to think fuel. I didn' do anything else yet, no comp check, nothing with the carb, etc. Any ideas? I did have a small engine shop for 15 years so I am competent in lawn mowers, motorcycles (older ones), chain saws, etc. but haven't done too much with outboards. I know a carb cleaning can't be too tough but looking for ideas first. Otherwise, I may see if the guy will stand behind it and pay for it to go to a dealer. Thanks for the help.

 

[Whoopbass]

Re: 1978 15hp Evinrude won't open up

Clean the fuel system from the tank to the carb and most likely it will be running like new again.
I find working on an outboard is a lot easier then a lawn mower so you shouldn't have any problems.
There's a carb cleaning procedure in the FAQ section that might help you.

 

[bgbass.1]

Re: 1978 15hp Evinrude won't open up

It may run ok at idle but check spark when it does it on the water at full throttle you could have a coil going bad

 

[wingsaircharter]

Re: 1978 15hp Evinrude won't open up

I cleaned the carb. It was clean already. Had a leaking fuel hose too. Ran good for 100 yards and then back to the same thing. Now it definitely does not have spark on lower cylinder. Switched plugs--same thing. Checked connections-good. Loosen and tighten ground-no change. Since top cylinder has good spark can it still be the electronic unit under the flywheel or the CDI...or does it have to be the coil. It is a 1978. Also, cold compression was about 90 on top and 85 on the bottom. I know that is not the problem but is that weak? Thanks.

 

[tashasdaddy]

Re: 1978 15hp Evinrude won't open up

complete swap the coil positons, if the problem follows the coil, replace the coil. compression, i would do a decarb.
Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck

that motor is not made to be run on muffs, needs a barrel.

 

[F_R]

Re: 1978 15hp Evinrude won't open up

wings, having had a small engine shop for 15 years, you certainly know that the carburetor feeds both cylinders. So, a problem with the carburetor will affect both cylinders, not just one. So, get your thoughts off of the fuel system...except for a possibly leaking fuel pump diaphragm which will flood one cylinder.

The 9.9 and 15 had terrible problems with plug fouling in the early days. But the 1978 has the CD ignition, doesn't it? From what I understand, that greatly improved them.

You could have a problem with carbon fouling of the plugs. You could also have a spark problem. That thing should throw a 7/16" spark. Make sure you are using the correct plugs. You could also have a water infiltration problem...water getting into a cylinder.

 

[wingsaircharter]

Re: 1978 15hp Evinrude won't open up

wings, having had a small engine shop for 15 years, you certainly know that the carburetor feeds both cylinders. So, a problem with the carburetor will affect both cylinders, not just one. So, get your thoughts off of the fuel system...except for a possibly leaking fuel pump diaphragm which will flood one cylinder.

The 9.9 and 15 had terrible problems with plug fouling in the early days. But the 1978 has the CD ignition, doesn't it? From what I understand, that greatly improved them.

You could have a problem with carbon fouling of the plugs. You could also have a spark problem. That thing should throw a 7/16" spark. Make sure you are using the correct plugs. You could also have a water infiltration problem...water getting into a cylinder.

F_R, thank you for your post. As I stated in my first post, the engine would run at idle with either plug wire disconnected leading me to believe that it was not a spark issue. I know, from the 15 years, that engines that have a single carb, can act the way that this acts when there is some water or dirt in the carb that with intermittently get sucked into the main jet causing it to run erratically. After cleaning the carb, and another test run, NOW the spark on the lower cylinder is gone after it warms up. In my last post, I said that so I KNOW that I have a "spark problem" as you mention. As Fleet Admiral, you certainly know that problems can be intermittent which makes a mechanic sometimes have to systematically make sure that certain systems are OK even though it seems as though that system probably is not the problem. Now that I know that it is a spark problem after warm up, it will be easier to attack. Thanks for your help.

 

[HybridMX6]

Re: 1978 15hp Evinrude won't open up

Do as Tasha said and swap coils. If it follows the coil, replace it, it it does not, look elsewhere up the system.

 

[wbeaton]

Re: 1978 15hp Evinrude won't open up

Yes, swap the coils and if spark follows the coil you need a new coil. If it doesn't then look to the powerpack. You should get around 20 mph on a 14' utility boat.

 

[wingsaircharter]

Re: 1978 15hp Evinrude won't open up

I tried to put the connectors out of the rubber boot so that I could swap the coils but they don't want to come out. I don't want to pull the connector off the wire. Is there an easier way to swap the coils?