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| 25HP JOHNSON HIGH AND LOW SPEED CYLIN... |
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Message |
    
John Drake
New member
Username: jcdrake
Post Number: 1
Registered: 07-2009
| | Posted on Monday, July 13, 2009 - 09:54 am: | 
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I have a 25 hp Johnson and after about 25 minutes of running it seems to cut a cylinder out at high and low speeds. It will run like this fora while then the 2nd cylinder comes back. I have put 2 new coils in and new plugs. Compression is 100 for both cylinders. Also put new fuel line on. Not sure where to look next. |
Joe Reeves
Senior Member
Username: joereeves
Post Number: 7666
Registered: 02-2001
| | Posted on Monday, July 13, 2009 - 10:48 am: |
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There are a lot of 25hp engines out there. It would help if we knew what year it is.
If that cylinder comes back suddenly, that usually indicates a ignition problem. Possibly the armature plate has a slight wobble to it, the coils (if magneto) are set wrong, are or the points are set wrong and/or are dirty.
(Point Setting Of Magneto Models)
(J. Reeves)
Set the points as follows. Have the flywheel key aligned with the fiber rubber portion of the ignition points. Adjust the gap so that a .020 gauge will pass thru but a .022 will not. Should there be any question of the points being dirty (touching the contact with your finger would cause them to be dirty), clean them with a small brush and acetone or lacquer thinner.
NOTE: Should the operating cam have a small portion on it with the word "SET" imprinted, align this portion with the fiber rubbing portion instead of the flywheel key.
Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:
http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store
(Magneto Coil Alignment)
(J. Reeves)
To align the coils properly, have the metal vertical portion of the coil yokes aligned with the inside edge of the bevel that exists on the top portion of the aluminum seat upon which the coils sit. This creates the proper distance between the coils and the flywheel magnets. Faulty alignment creates friction and the yokes of the coils heat up, turn blue and expand.
Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:
http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store
(Magneto Armature Plate)
(J. Reeves)
If the armature plate has a a loose fitting, wobbling motion (the plate that the points, coils etc are attached to), it is usually caused by a slightly worn support ring. This allows the point setting to change erratically as the armature plate turns.
The cure is to remove the armature plate so that the support which is attached to the powerhead with 4 screws is visible. Then, with a screwdriver and hammer, or some tool of your choosing, and looking straight down at the support ring, make an indentation at what would be called the 12, 3, 6, and 9 O'clock positions. Install the armature plate and check for a smooth turning wobble free movement.
You may need to do that procedure a few times to obtain the proper fit (not too tight, not too loose), but it's worth the effort.
Use a small amount of anti corrosive grease between the aluminum ring and the brass support plate and also on the brass bushing of the armature plate when all is well.
Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:
http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store |
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