same old problem

[george3405]

Earlier this year I asked for help with my 1989 Evinrude 48SPL problem. It cranks over, but backfires through the exhaust and won't run. I had changed the power pack (all hooked up correctly), changed plugs, wires (2cyl) and coil pack. I also overhauled the carbs and changed out the gas. The wires are not crossed and the piston on #1 is in correct position when trying to fire. I even pulled the cylinder head and all is well. The only thing I can think of is maybe I got the wrong power pack. The shop I bought it from (the power pack) said it was the only one for that motor. After I installed it the flywheel rubbed a scratch in the case of the power pack because I didn't have it aligned perfectly. Could a scratch cause it to short out. By the way the flywheel key is fine/no slippage. I really like the boat and the motor, but this is really getting frustrated. I even had my neighbor send someone over who said the screen in the exhaust gets clogged and causes this problem. Guess what? This engine has no exhaust screen. Any help is greatly appreciated! I've had this boat since Jan. 22, 2007 and have never been able to run it.

 

[tashasdaddy]

Re: same old problem

what are your compression reading?

 

[george3405]

Re: same old problem

Tashasdaddy,
I had performed a compression check awhile back and 1 cylinder was fine and one a little low. Would that cause such a backfire through the exhaust. Right now the head is off the block.
Thanks,
George

 

[CharlieB]

Re: same old problem

Backfiring out exhaust is caused by timing way out of line.

You've already ruled out a sheared flywheel key.

My vote is plug wires are reversed.

 

[TigerSharkCrazy]

Re: same old problem

Or it could be scored cylinder walls letting compression passed the rings.

 

[george3405]

Re: same old problem

Scored cylinder wall maybe. I need to check. I used the rope in the spark plug hole when I went to remove the flywheel nut. When I went to remove the rope it was jambed up too tight. Finally I got it loose by really turning hard. One cylinder does seem low. Could it be stuck rings? When I got the boat the fuel had absorbed a bunch of water and been cranked over and did not start. I have the head off and I will check the cylinder walls. Any ideas how to free up stuck rings without tearing down the engine?
By the way, the plug wires I know are not crossed. I already checked all wiring thoroughly several times.

Thanks,
George

 

[Ranger 330V]

Re: same old problem

george did you ever figure out what your problem was?? Sounds JUST like mine...I have a 79 140 and it does the same thing. I have replaced the stator, trigger, rectifier, and both powerpacks. I still have the backfire. I can't figure it out. I'm not a parts replacer by any means but I feel like I am now. Flywheel is all fine...compression is 120 on all cylinders...its just driving me nuts. I have a two page thread going right now about this maybe you'd want to read through it. Just wondered if you figured anything out. Thanks.

 

[george3405]

Re: same old problem

Ranger,
I know I found the greatest if not the entire problem. Eventhough I hooked up my new powerpack identically to the old one it turns out it was firing #2 cylinder when #1 cylinder should have been firing. Now the gas is old again so I have to change that out and do some other things and then I will be able to check and see if it runs.

Remove your spark plugs, ground the plug wire terminals, and hook a timing light with an inductive pickup to one plug wire, and point it at the timing marks while cranking over your engine. Do this to each plug wire and if the #1 cylinder timing marks are 180 degrees off (on a 2 cylinder) then you know that the plug wires are hooked up wrong. Be sure plug wires are grounded or the timing light won't flash.

I hope this is helpful. If it isn't clear contact me and I'll try to clarify any of your questions. My email is george3405@yahoo.com

At any rate let me know hwat you find.

Thanks,
George3405

 

[Ranger 330V]

Re: same old problem

I'm going to try that tonight..and work on the carbs some...I know what you mean about the timing marks...they should all be 90 degrees apart on my engine. I'm going to do it tonight so I don't have to try to see it so hard. Someone is firing at the wrong time...I just have to isolate him. I'm going to be mad if it turns out to be a 20 dollor coil or a link and sync (carb) problem and I've spent this money...but at least I'll know what I've got..lol. I'll let you know.

 

[Joe Reeves]

Re: same old problem

Firing (backfiring) out the exhaust port can be caused only by having the ignition system fire a particular cylinder when the exhaust port is open (piston down). THis would sound like a shotgun going off..... is this the condition that you're experiencing?

This can be caused by a sheared flywheel key, or a flywheel with melted (moved) center sensor magnets if they exist, or having the timer base leads routed incorrectly to the powerpack, or having the leads from the powerpack to the coils reversed to mention a few.

I realize that your powerpack is located on the timer base rather than on the powerhead, so the timer base to powerpack lead mention is pretty well moot. I left it there for others than may have the backfiring problem where it would apply.

The carburetor, regardless of its condition would have no bearing on a backfiring problem.

The original part number of the powerpack associated with the 1989 48hp Evinrude or Johnson outboard is 583984 and has been superseded up to 584329 and finally to 584489. A powerpack with any of these part numbers would be suitable for your engine.

The scratching of the new powerpack..... If you do not have a special tool which is a centering locating ring, do the following.

Notice the seating area where the powerpack sits upon. There are slight bevels there. Align the powerpack's vertical area so that they are aligned with the inside portion of those bevels. This will give a near perfect position of the powerpack in relation to the flywheel magnets.

When time permits, visit my store (copy/paste) at: stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc

 

[george3405]

Re: same old problem

Joe,
Thank you so much. Your input is excellent! I appreciate the help. Later this evening I will be visiting your Ebay store.
Thanks again!
George3405