1983 Evinrude 15hp Problem -Backfire+etc

Hey there.
Motor: 1983 15hp Evinrude 2 cycle outboard shortshaft.

History of motor since Ive purchased it about 2 months ago: So since then I have changed the spark plugs twice, added new seal/gaskets to all the parts including Powerhead. Replace Grommets for exhaust/water pipes, new impeller, added thermostat, new prop with higher pitch, unglogged and cleaned parts where the water is supposed to circulate. New Spring coil for pull start!, and I was told from seller that the carb has been rebuilt along with new fuel pump. I also purchased a seloc vol.2 manuel, but its really unhelpful.

Problem: After taking motor/boat out for a day (everything is working). Get it home and clean/store away...... So, One week later I get the boat out, and the motor will not start. ? No matter how many times I pull the chord, nothing kicks on? And once the pressure inside builds up, the motor backfires. I believe it backfired out the propeller, and carburator at one point.

So, my list of things Ive checked:
-Spark Plugs and battery packs are producing nice blue sparks.
-Fuel is getting to the fuel pump and into the carburator.(the more times you pull the "pull start" gas seems to build inside the filter where the carb lets out.
-Im not sure if fuel is getting inside the power head though?
- unclogged the exhaust pipe and water pipe.
- All the plugs are hooked up correctly as stated above....
-So :/ after doing everything, I have had 3 failed attempts on getting this motor to fire on. Its like a create a hypothesis, go out and prove it, then fail.


So thats pretty much the best /fastest way to explain the issue. Any help would be awesome. I have spent a huge great deal of time, and money so far by just working on it myself. So, thats why I have no idea what to do. And yes, I am a first time boat owner, but after pulling that power head out, Ive learnd alot.

Thankyou for your time,
Andrew

Re: 1983 Evinrude 15hp Problem -Backfire+etc

Welcome to Iboats. 3 things required to get this puppy running, fuel, spark and compression. You've ruled out spark and you think it's getting fuel, what about compression? You need to check the numbers with a compression gauge and report back. You mentioned you replaced gaskets, was the head off of it when you did your service to the motor?

Re: 1983 Evinrude 15hp Problem -Backfire+etc

bktheking said:

Welcome to Iboats. 3 things required to get this puppy running, fuel, spark and compression. You've ruled out spark and you think it's getting fuel, what about compression? You need to check the numbers with a compression gauge and report back. You mentioned you replaced gaskets, was the head off of it when you did your service to the motor?

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Thanks!Ok will check compression and report back, but while testing it, i pulled one of the two spark plugs out and I do feel air blowing out when the flywheel turns showing that there is a type of compression. Yes, I took the head off while servicing it. Replaced the old seal/gasket with new ones shipped from evinrude.com just today actually, along with the two manifold seals (because i was checking for broken reed valves, which there aren't any!(very good shape too ). I shoud've taken more pics but while reading other posts of the forums I heard something about keys..... Well I think my flywheel key is ok. Here are some pictures I just took a few minutes ago...

Re: 1983 Evinrude 15hp Problem -Backfire+etc

I have an 83 but a 9.9, same diff, I've worked on several of these motors so I know them pretty good. So new head gasket rules out a head gasket issue. What plugs are installed and what are they gapped at? The only time I had mine backfire was reversed plug wires. Put the flywheel back on and torque it to spec. As a test, remove the black intake from the carb, 4 screws on the top, 2 inside. Choke off, spray 50:1 mix into the carb and pull it over and see if it starts, report back.

Re: 1983 Evinrude 15hp Problem -Backfire+etc

bktheking said:

Choke off, spray 50:1 mix into the carb and pull it over and see if it starts, report back.

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Ok so when you say spray 50:1 mix into carb, your referring to my gas mixture, and just somehow poor inside the carb with the intake off?

+ I could not recall what my spark plugs were gapped at but I guess if i had to say it would be standard. I have not messed with the spark gap at all. Because the motor ran before, and I have kept all the settings the same just as before. The plugs are also in correct function with the electric configuration.

Re: 1983 Evinrude 15hp Problem -Backfire+etc

Panfishangler1 said:

Ok so when you say spray 50:1 mix into carb, your referring to my gas mixture, and just somehow poor inside the carb with the intake off?

+ I could not recall what my spark plugs were gapped at but I guess if i had to say it would be standard. I have not messed with the spark gap at all. Because the motor ran before, and I have kept all the settings the same just as before. The plugs are also in correct function with the electric configuration.

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I'm saying take a spray bottle and put some 50:1 mix in it. Remove the black plastic intake from the front of the carb and spray some fuel into the carb with the choke open. If it fires then we will know that it's a fuel delivery problem. If it doesn't start at all then it's something else. Plugs should be l77jc4 or ql77jc4 champions gapped to 30 or 40 depending on which manual you read.

Re: 1983 Evinrude 15hp Problem -Backfire+etc

bktheking said:

I'm saying take a spray bottle and put some 50:1 mix in it. Remove the black plastic intake from the front of the carb and spray some fuel into the carb with the choke open. If it fires then we will know that it's a fuel delivery problem. If it doesn't start at all then it's something else.

Ok so I sprayed alot of mix into the carb, and pulled a bunch of times, but no go . No turn on. No backfire either, so ya...

(pic just to get visual)

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Re: 1983 Evinrude 15hp Problem -Backfire+etc

Going back to where we started, compression test. Don't like that pic, take a pic of the cam roller where the carb makes contact with the magneto plate, something doesn't look right, take it so I can see everything, not a close up. Make sure the tiller handle is set to the start position on the twist grip.

Re: 1983 Evinrude 15hp Problem -Backfire+etc

The 3 things you need for a motor to start are good/evencompression, the correct fuel/air mix and timed spark. If it backfires thru the exhaust the spark could be incorrectly timed. One cause of that is a sheared key or crossed plug wires. You key appears to be OK in the pics. The plug wires appear to be correct IF the coil primary wires are correct. It's not uncommon to get the coils swapped when the head was off and the coils get put back on incorrectly.

If it's "backfiring" or spitting thru the carb throat it can be an air leak, too little fuel mix or a very slightly open throttle butterfly.

If the carb is flooding slightly the fuel mix may not be able to ignite in the combustion chamber but as enough get's into the exhaust it may ignite from either cylinder trying to fire and resulting in igniting the unburned fuel in the midsection/ exhaust.

Re: 1983 Evinrude 15hp Problem -Backfire+etc

bktheking said:

Going back to where we started, compression test. Don't like that pic, take a pic of the cam roller where the carb makes contact with the magneto plate, something doesn't look right, take it so I can see everything, not a close up. Make sure the tiller handle is set to the start position on the twist grip.

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Just going back to the pic, when you twist the throttle to the start position that black throttle cam on the mag plate should make contact with the roller on the carb in order to open the butterfly on the carb a bit to allow air in. If it isn't making contact the tiller gears could be out of sync causing it not to allow the correct air/fuel mix at startup, hense the backfire. The tiller gears are the weak link on this motor, twisting the grip while the handle is upright can throw the gears out of sync causing you to think it's set to the start position while not advancing the plate causing the butterfly not to open.

Re: 1983 Evinrude 15hp Problem -Backfire+etc

bktheking said:

Going back to where we started, compression test. Don't like that pic, take a pic of the cam roller where the carb makes contact with the magneto plate, something doesn't look right, take it so I can see everything, not a close up. Make sure the tiller handle is set to the start position on the twist grip.

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This is motor in Neutral with Throttle on START


2 pictures of The motor here is in Neutral with Throttle on FAST

Re: 1983 Evinrude 15hp Problem -Backfire+etc

Sometimes these motors won't start with throttle set on start. My motor starts on fast, I set it so it hits the lockout. Once it's warmed up I can back it off. Have you tried starting it with the throttle set to fast? Pull the plugs and see if they are wet, it won't start if they are soaked.

http://www.sschapterpsa.com/ramblings/Johnson_9.9_carb-fuel_pump.htm

Have a look at the timing section, check your to make sure everything is set right.

Other question, carb been cleaned? and if so,


Have you screwed the idle screw in all the way till snug and back out a turn and a half?

That and I have to ask, you used a torque wrench on the head and bolted it back down in the proper pattern? Gotta ask as it's important that it is done properly, it's part of the variable.

Re: 1983 Evinrude 15hp Problem -Backfire+etc

bktheking said:

Have a look at the timing section, check your to make sure everything is set right.
Other question, carb been cleaned? and if so,


Have you screwed the idle screw in all the way till snug and back out a turn and a half?

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Yes, the Carb was pulled out and everything seemed to be not clogged, but checked and the passage ways were clear. The low speed needle was correctly turned 1 1/2 after i replaced the little grommet ring that goes in there. I guess I can check the timing.

+ will check that link too, I havent seen that one yet lol.

Re: 1983 Evinrude 15hp Problem -Backfire+etc

Try throwing a new set of plugs in it. Two stroke spark plugs can look alright but if your fuel air mix is a little off it can burn out your plugs but still get a small spark. My motor does that, first time it happened I was like what the hell it gets spark, but I throw a new set of plugs in it and it fires right up. It's on my long list of stuff to do. Anyways I'm not saying thats it but is worth a try.

Re: 1983 Evinrude 15hp Problem -Backfire+etc

Do yourself a favor and get an OEM shop manual ... try Fleabay 1st (least expensive) or outboardbooks.com

Re: 1983 Evinrude 15hp Problem -Backfire+etc

wilde1j said:

Do yourself a favor and get an OEM shop manual ... try Fleabay 1st (least expensive) or outboardbooks.com

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Gotcha Well the one I bought a few weeks ago is this one Below. It doesnt really help with my issue. It points out things, but Im still in the process of finding what the problem IS! What i would like to look more into is TIMING with this motor. So, by any chance that if I can get all the information about sychronizing/timing this 1983 15 hp 2 cycle motor, that would be awesome.

Re: 1983 Evinrude 15hp Problem -Backfire+etc

Not necessarily timing, it's pretty static on the motor if the key is in tact. The only other timing is what I sent you yesterday in the link. I'm going back to that magic word, compression.

Re: 1983 Evinrude 15hp Problem -Backfire+etc

hi I have a nearly identical problem with my 1982 25hp johnson so i feel your pain
i have the OMC shop manual for all 1982 omc's. I am not sure how different the 82 15hp is from the 83 15hp but if you want i could scan the timing and link & sync pages and email them to you or post them for you

Forrest

Re: 1983 Evinrude 15hp Problem -Backfire+etc

Compression Update: So I bought a compression test kit tonight, and plugged it in to the spark plug hole... It read 0 compression for both plugs. Am i doing something wrong? How can this be?

Re: 1983 Evinrude 15hp Problem -Backfire+etc

FAC said:

hi I have a nearly identical problem with my 1982 25hp johnson so i feel your pain
i have the OMC shop manual for all 1982 omc's. I am not sure how different the 82 15hp is from the 83 15hp but if you want i could scan the timing and link & sync pages and email them to you or post them for you

Forrest

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Hey Forrest. That would be really helpful. It wouldn't hurt to see more information on Timing. I will pm you my email.

Andrew