my 18hp missin bad

[huntxtrm]

My 18 hp evinrude 1973 model, is missing real bad. I've installed new points and condesors, didn't fix the problem. Rebuilt the carberater, didn't fix the problem. rebuilt the fuel pump, didn't fix the problem. At this rate i'm gonna wind up with a new 1973 evinrude 18 hp, if i keep rebuildin stuff. What could cause this. Coils? how can I check them? spark is ok, not super hot same as it has always been. Fuel tank? Fuel hose? Float level? primer bulb pumps up, start engine and run for a while, you can pump it up again. I thought the bulb was supposed to remain hard while running? Some tell me no. Please help!!!!!!!!!!!!

 

[jonesg]

Re: my 18hp missin bad

no bulb dosen't stay hard once its running.

Compression and spark test first, then look at ignition.
Sounds like spark isn;t what it was...if so ..coils plugs and wires.
To me thats all part of a complete tuneup which they need on occasion.

 

[F_R]

Re: my 18hp missin bad

So, can you describe this missing better? When does it happen, idle? High speed? Are you sure it is missing and not coughing/sneezing or jumping out of gear?

A good coil will jump a 1/4" spark gap. Testing spark with the plugs laid against the head is better than nothing, but really not much of a test.

Can we assume you have tried new spark plugs? Even new ones can carbon foul from bits coming loose from the head and sticking between the spark gap and cause a high speed miss. We used to see it all the time in the days before TC-W3.

True "missing" is an ignition related problem. You are wasting your time and money messing with the fuel system.

However, coughing or sneezing only at idle is a fuel problem (too lean).

 

[huntxtrm]

Re: my 18hp missin bad

I have also installed new plugs, forgot to mention that. I did a compression test, both cylinders around 90 psi. only ingnition I haven't yet installed are the coils, They fire but not a super hot spark. I was told that type of ignition doesn't fire that hard. It is basically like a lawn mower set up x 2. Is it supposed to fire real hard? Lots of smoke when idling,, plugs are wet after running. Maybe coils are week? Thanks for your help and quick response. Us beginnners need all we can get.

 

[huntxtrm]

Re: my 18hp missin bad

OK, I checked out the whole fuel system. I thought I had it fixed, went to the lake, started doing it again. It seems to run ok, until it is under a load. I put it in gear, motor missis, coughs, sneezes, farts whatever you call it, so bad the motor jumps like it's gonna come off the boat. The only thing, I can think of is the coils. Spark is not thick, hot spark at the plug. Or like I think it should be. Is there a way to ohm out the coils to check them, or is sparking the plugs the only way. Or is there something else i'm missing? Reeds ok, fuel pump good, fuel pressure good, carb rebuilt,, carb clean, installed a inline fuel filter to insure carb does not get dirty, float level is correct, points and condesor are new, spark plugs are new and the higher heat level, fuel is fresh and mixed 50:1 super unleaded, compression is ok, HELP!!!!!!!!PLEASE!!!!!! Thanks for the help fellas, together we can defeat this cantancerous evenrude.

 

[14ftgrumman]

Re: my 18hp missin bad

Get rid of the higher heat range plugs. If you ever get it running, you will melt pistons.
I beleive that it was born with J4 Champions.
Put them back in.

 

[huntxtrm]

Re: my 18hp missin bad

I was told by the parts house, it is a factory spark plug. They said they spec 2 heat ranges, he gave me the hotter plug. Is he full of it, is my motor in jepordy?

 

[14ftgrumman]

Re: my 18hp missin bad

Your parts house is full of dummies. There is only one correct heat range. When you go to get the right plugs, ask nicely to see the catalog that the parts guy uses to find the plugs. You should have champion j4 or AC m42. Both are listed on the BRP parts charts. Look up Champion spark plugs on line.
I am currently running NGK's, but have also had good luck with Autolite. As long as you are using the spark plug manufacturer's recommended heat range, you should be good to go.

 

[huntxtrm]

Re: my 18hp missin bad

OK, checked the coils, they seem to be good. Checked them by utube video I found on the forum, very informative. Thanks. Any way, what next. Could it be a timing problem? I set the point by the book, I have. I did not do the strobe light method, I just set the gap. Is that my mistake. It misses slightly when idling, tries to jump off the boat when under a load(when I have the prop ingaged and running on the lake), makes me think timing issue. Is there a shear key like on a lawnmower. I saw a key, but it looked like steel, not alluminum.

 

[perkdp]

Re: my 18hp missin bad

Did you get it fixed ?

did you link / sync the carb ?
sounds like the high speed jet may be clogged and/or leaking air somewhere.
my 1973 X 18 acted like this with DOA-New plugs.

 

[huntxtrm]

Re: my 18hp missin bad

yes i did, It turned out to be the shifting dog. It was jumping in and out of gear. Felt like a hellofa miss to me. Changed dog, runs like a champ. Shifting dog that was in there barely had rounded corners making it jump like the dickens. lesson learned!