1978 evinrude 25 HP timing is a mystery

[brobab]

I have looked everywhere to find out how to adjust the timing on this motor. It was running great and then the stop screw on the throttle rod broke. Now it will start, but on the water, it will not run at wot, and will eventually not start at all. Black sludge comes out of the exhaust. The roller is adjusted so that it is in line with the mark on the cam. I found one vague reference to lining the flywheel marks up with the electric starter pinyon. I have a timing light, but am lost from there.

I would appreciate it if anyone could point em in the right direction.

 

[oldboat1]

guess I don't know what the "stop screw on the throttle rod" is. Might be reasonable to think it's a timing issue, but not getting it so far. Maybe try another description of the problem(s)?

 

[Chinewalker]

It is VERY difficult to mess up the timing on those motors. More than likely, your issue is elsewhere. The screw you refer to sounds like an idle stop adjustment screw. Doesn't do much more than set how low the motor will idle.

 

[brobab]

Thanks both for the replies - cant post photos yet, but soon. I am going to reclean the high speed jet again as a first step. Then will explore more aggressive issues

 

[oldboat1]

yup. pics could help. strikes me your intuition about timing might be correct if the flywheel key partially sheared (might explain the sudden occurrence too). If the flywheel jams on a slightly different spot on the shaft, it could produce the problems you describe.

 

[brobab]

Virtually every repair thread here starts with, "check compression, check for spark." So as I was getting ready to pull the flywheel and see about key shear, thought... well, lets check compression and check for spark. Checked compression - 130 both cylinders - great! Checked for spark. Cylinder 2 - jumps 7/16 strong blue spark. Cylinder 1 - NO spark!. Went ahead and also checked the thermostat - clean and functioning. Checked the impeller - clean and functioning.

So, about to look at replacing the coil when it occurs to me that the timing light strobed just fine when connected to the #1 wire. Could it just be the boot?

Suggestions? - spend $ on the multimeter, or just replace the coil and the wire? If I replace the coil, should I just do both at once?

 

[AlTn]

you can pull the boot off, pull the terminal end < spring > out of the lead, cut ~ 1/2" of the lead off, reattach the spring and boot and give it a test...if the timing light was flashing brightly when clipped on the lead, you should now have a strong spark..if not...post back

 

[oldboat1]

well done. Basics first. Tip I learned here some time ago: When connecting the spring connector in the boot, expose and peel back the stranded wiring, and butt it and the core against the spring connector to ensure a good connection.

 

[brobab]

No Title

Well... shoot. The boot fix would have been so easy. Still no spark. It looks like the coil is the original 1978 version, so I suspect there is a break somewheer further up the wire. Also, with this coil, the wire comes directly out of the coil bottom, so there is no opportunity to just replace the wires. New coils are on the way.

 

[AlTn]

with one good coil you could have switched it to the upper cylinder and checked the spark...if the spark returns to the upper cylinder with the good coil in place, then your
upper coil was the problem, if the spark is still absent with a known good coil in place then the power pack is suspect ...if that top coil's grounding point is corroded it'll fail to work also...anyway, something to check while awaiting parts...new coils arrive and installed,< last ones I replaced on that same CDI setup didn't have separate ground wires, but grounded through a band that the coil mounting screws go through> and the top cylinder still has no spark, replace the power pack

 

[brobab]

AITn must be psychic. Tried just what he suggested. No spark. New coils came - tried with new coil - no spark. Before I order a new power pack, I am going to check continuity from the power pack to the non sparking coil - but I also suspect the power pack.

Question - could it be an issue starting at the coil.magneto under the fly wheel? Do I just work backwards and start with the power pack - then worry about the magneto?

 

[oldboat1]

I'll bow out because I'm not very good at testing the CD parts, but the sensor, charge coil and power pack should run about $125 if you elect to just do replacements. The stator is another story. I did find in working on smaller motors earlier this summer that flywheel magnets can go bad, so can test those easily enough by pulling the flywheel and dangling a small screwdriver by the magnets. (actually, was the flywheel and either the sensor or charge coil -- or both -- in the motor I had difficulty with -- spark on one plug. I just replaced both the charge coil and sensor along with the flywheel.)

 

[AlTn]

highest probability is the power pack with that CD1 ignition when you have no spark to 1 cylinder with a known good ignition coil installed...you can test for voltage going to and out of the power pack.....reference cdielectronics.com/troubleshooting....cdi p/n: 113-2453 for the pack

 

[brobab]

Just to close this out. It was the power pack. Installed new pack and engine runs like a champ. As a result of my hit and miss diagnostics, new coils, new plugs, new spark plug wires, checked thermostat and installed new gaskets, cleaned carb and installed new gaskets, verified compression and degreased engine. Idles great. Starts on first crank. Probably good to go for many more years. Learned quite a bit in the process. Thanks for all the helpful comments.

 

[oldboat1]

good ending. thanks for the post!