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Joe Reeves Timing Method on 93 Johnson 25hp

K

Klink

Regular Contributor
My engine all the sudden would not run at high speed, and so I gave it gas with the electric choke and it would speed up, so, I determined by that simple test that the carb high speed jets were clogged. Therefore, I did a carb rebuild and a synch & link. I then checked the timing using the Joe Reeves method and found the engine was reading 30 degrees. My manual calls for 30 +-1 degrees, therefore, I re-set the timing using the Joe Reeves method from the 30 I was reading, to 27 degrees (Joe Reeves calls for -4 degrees which would be 26 degrees, however, I could not get the stop screw to go any lower than 27)

Here's my problem now:

The engine seems to run with less power now. I didn't have a tach before, but I feel the boat ran faster. With some excess weight on the boat, it is very slow. To re-phrase what I wrote above, apples versus apples, I retarded the timing from 30 to 27. Another problem that I did not notice before is that at WOT, I hear a slight rattling noise, which could just be something external under the cowl, or could it related to the retarding. Maybe this particular model should run at minus 0 degrees using the Joe Reeves method?

What happens if an engine is advanced or retarded from the factory spec, what effect, signs does it show in either case? How does it perform in each case. I am tempted to return the timing to say 29.
 
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Klink said:
I retarded the timing from 30 to 27. Maybe this particular model should run at minus 0 degrees using the Joe Reeves method?

What happens if an engine is advanced or retarded from the factory specifications?
Click to expand...

From another thread http://www.marineengine.com/boat-forum/showthread.php?10846-1989-Johnson-Timing Joe Reeves says:

"If you set the engine to its true setting at cranking speed, when running it will advance beyond its limit by 4 degree; which will set up pre-ignition causing guaranteed piston damage! You don’t want that to take place".

My Questions:

1) What are signs of pre-ignition? Seems to me that it might show itself when starting the engine, being as the piston is fighting the fuel ignition?

2) Is this minus 4 degree etched in stone? My engine was running at almost +1 before I changed it to -3, and it ran fine before, seems like it ran better.
 
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If engaging an electric choke or the fuel primer solenoid resulted in a return of power, then obviously the problem is a fuel related one. If the engine ran okay previously and you owned it for some time, it's safe to assume that the timing was set properly however it's now been changed and apparently is causing another problem. I'd suggest you put the timing back where it was for the time being.

The 4 degree difference was stated in a bulletin issued by OMC many years back so yes, I would say it is etched in stone.

Signs of pre-ignition is usually having a spark plug fail due to bits of melted aluminum flaking off a piston that's melting down.

Does that engine incorporate the "Fast Start" feature? I retired in 1991 so I'm not familiar with your engine's design and circuitry. If it does have the fast start feature, it sounds like you failed to disconnect it before checking the timing.... If it does not, then your initial test should have shown the timing at 26 degrees BTDC, not at the actual 30 degrees at which it runs at full throttle.

You're overlooking something but without being there, I"m at a loss to tell you what it is..
 
joereeves said:
If the engine ran okay previously and you owned it for some time, it's safe to assume that the timing was set properly however it's now been changed and apparently is causing another problem. I'd suggest you put the timing back where it was for the time being.

Does that engine incorporate the "Fast Start" feature? I retired in 1991 so I'm not familiar with your engine's design and circuitry. If it does have the fast start feature, it sounds like you failed to disconnect it before checking the timing.... If it does not, then your initial test should have shown the timing at 26 degrees BTDC, not at the actual 30 degrees at which it runs at full throttle.
Click to expand...

The engine is a 1993 25 hp, it is identical to the 1991, and who knows how long back. It does not have the fast start feature. It was set at 30+ .

I'm going to try it tomorrow in the water at 30 and see how it does.
 
On second thought, my Johnson 25hp timing reads up front at the starter, so it is not so hard to test on the water at WOT (on a flat day, with a good co-driver). I ordered an induction timing light with a bright Zenon light and I'll check the current timing before I re-adjust anything.

My 115 Johnson on the other hand reads at the stern and there is no way I would take the risk of doing it while running. Luckily the Joe Reeves method worked like a charm on that engine.
 
Klink said:
On second thought, my Johnson 25hp timing reads up front at the starter, so it is not so hard to test on the water at WOT (on a flat day, with a good co-driver). I ordered an induction timing light with a bright Zenon light and I'll check the current timing before I re-adjust anything.
Click to expand...

Bought an Actron CP7527 Inductive timing light which advertised as having "a strong Zenon light that works even in sunlight". And went and tested the maximum spark advance on the water. It was not hard to do, I just sat in the back bench and red the mark I had made at 26 degrees (30 degrees minus 4 degrees, the Joe Reeves method) , and it read the same 26 degrees. It should have read 30 degrees, but there was no difference between the maximum spark advance set with the Joe Reeves method with the starter motor, and the real world reading in the water. It appears that on my 1993 Johnson 25hp, one has to set the Joe Reeves method at 0 degrees off the factory specified maximum spark advance.

I will re-set it with the Joe Reeves Method tomorrow to 30 degrees, that is, the Joe Reeves Method but minus 0 degrees.



P.S.- the timing light did show my white mark in the sun, it was not as bright as in the dark, but I could clearly see it. The inductive pickup is a big step up compared to my 40 year old timing light, which I will now retire.
 
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Tested the maximum spark advance in the water at WOT, it was at about 28, so I advanced it to 30 (the factory spec) on the water at WOT.

BOTTOM LINE: Looks like on my engine one has to set it at +2 over the factory spec using the Joe Reeves method, then finish it in the water at WOT.
 
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