1958 evinrude 18 hp back fires thru exhaust

[Fastwin18]

This motor has less than 100 hours on it. Has been in storage since 1973. It was serviced and put away. The timing is correct, the plug (new) gap is 30, the points (new) are set at 20 and each open at TDC. It has new cylinder coils, but it won't start it only back fires thru the exhaust. It is getting fuel. I only pull the choke out to the first notch and the high speed adjustment knob is open 1/4 turn and it won't start so I pull the choke out full and it back fires thru the exhaust. Not electric start. No fuel pump it has the fuel tank and pressure button. I would like to get out fishing. Thanks in advance for your help...Fastwin 18

 

[The-Machinist]

Re: 1958 evinrude 18 hp back fires thru exhaust

I would start by confirming that you have a fat white spark that will jump 7/16" on BOTH cyl. Pick up a cheap spark tester at the part store if you dont already have one. Also, have you checked the flywheel key? If the flywheel wasnt properly torqed down it could have partially sheared during one of your "backfires".

 

[Fastwin18]

Re: 1958 evinrude 18 hp back fires thru exhaust

Thanks themasterofmachines for coming back. The flywheel key is fine and the flywheel is torqued properly. I will check the spark. The plugs are from 1973 never turned over or had they attempted to start after the service. The plugs are J6J's.

 

[The-Machinist]

Re: 1958 evinrude 18 hp back fires thru exhaust

If your motor still has the original coils go ahead and replace them. They arent expensive and will save you from getting towed when they do burn out.

 

[F_R]

Re: 1958 evinrude 18 hp back fires thru exhaust

There is one reason for backfiring out the exhaust. The motor is out of time. Plain and simple.

What is not so simple is why it is out of time.

1. Spark plug wires reversed

2. points set way off out of spec

3. Breaker cam upside down

4. Flywheel key sheared.

5. Coil wires going to wrong set of points.

 

[tmcalavy]

Re: 1958 evinrude 18 hp back fires thru exhaust

Also note that the baseline settings are 3/4 turn out from seated for the high speed needle and 1 and 1/2 turns out for the slow speed needle. When I start mine cold I pull the choke completely out, set the tiller to Start, pull the cord until it fires, let it run with choke on until it wants to die then push the choke in. Even if it dies after that it will generally fire and go on subsequent pulls. Once it's run a while and warmed up it should fire/run with only a light pull on the cord.

 

[flyboy712]

Re: 1958 evinrude 18 hp back fires thru exhaust

adjust the fuel mixture settings sounds like it is probably too lean. Mine did the same thing til I got it adjusted correctly.

 

[Fastwin18]

Re: 1958 evinrude 18 hp back fires thru exhaust

Thanks for the input. Firstly the points are set at 20 which is spec, the wires are properly connected, the breaker cam is right side up, the flywheel cam is like new not even a burr, the coilwires are going to the right set of points. Second the coils are new. I'm going to check the spark...7/16 in length and will adjust the low and high speed needle settings, I currently have the slow speed off and the high speed 1/4 to 1/2 turn and the choke at half way notch. Thanks again for all the good info....Fastwin18

 

[mikesea]

Re: 1958 evinrude 18 hp back fires thru exhaust

be sure the timing base under the flywheel is rotating as it needs too,I believe thre is a rod from the throttle with a locking device that pushes the timing base,often the timing base gets gunked with old grease and wil not rotate properly causing timing to be off at start and run

 

[Fastwin18]

Re: 1958 evinrude 18 hp back fires thru exhaust

Thanks Mikesea: I didn"t know what that was, I appreciate the heads-up. Thats great. I also picked up a new set of plugs so they are fresh and give a good spark...Fastwin18

 

[Fastwin18]

Re: 1958 evinrude 18 hp back fires thru exhaust

I have done all the things that have been suggested, also put new plugs in. I now agree it must be in the timing. The points are opening at TDC when you look thru the inspection hole in the flywheel. Can you adjust the timing either retard or advance? If so how? Fastwin18

 

[F_R]

Re: 1958 evinrude 18 hp back fires thru exhaust

There is no timing adjustment. The armature plate rotates back and forth to change timing as related to throttle settings but only within it's limits, which cannot be changed.

I stand by my previous list of possible causes for backfiring.

 

[Fastwin18]

Re: 1958 evinrude 18 hp back fires thru exhaust

I would like to thank imported_F_R,mikesea,flyboy712,tmcalavy, and themasterofmachines, for their help and input in assisting me in finding the problem I am having with my 1958 evenrude 18hp. The engine still hasn't started yet but I have replaced all the parts and have put a volt meter on and get 6 and 10 on the plugs. I guess its just playing with the fuel needles now. I have lots of gas and lots of spark.it just backfires so it must be flooding. The flywheel key is fine. I have done all that each of you have advised. Thanks again for your help, I appriciate it...Fastwin18

 

[Chinewalker]

Re: 1958 evinrude 18 hp back fires thru exhaust

Double check the plug wires going to the right plugs. FRONT coil feeds the TOP cylinder. Points should be gapped at .020 with the fiber rider of the points aligned with the crankshaft keyway.

- Scott

 

[Fastwin18]

Re: 1958 evinrude 18 hp back fires thru exhaust

Hi Chinewalker: Yep they are right, front to top and back to bottom and the points are gapped at .20 aligned with keyway. Thanks...Fastwin18