Jonhson 25 cyl head?

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laujok

Seaman Apprentice
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Sep 9, 2011
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48
Re: Jonhson 25 cyl head?

Okay, I have tried plug wires from my other motor and checked resistance (about 0 ohms both). And original wires have 0 ohms too. The coils have a mounting tab for grounding and the upper mounting bolt goes through the tab. Tabs are shiny and the mounting surface is clean. I was wondering, could it be possible that the power coil is too far from the fly wheel magnets and because of that giving less power to the ignition system? But when I changed the Power coil last year I did mark the spot where the old one used to be. The old PC was dirty but gave 856 ohm resistance. New one gives almost the same. I haven't checked any voltages from this motor.
I have L77JC4 plugs on it, tried also with Bosch W4AC, Champion L78V and NGK B6HS. No affects...

I think about giving one or two more chances for this motor. I got it so cheap that I think it's worth fixing being only 12 years old..
 
H

Haffiman

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Re: Jonhson 25 cyl head?

When you changed coils, did you get them close enough to the fly-wheel? As close as possible but not touching.
 
L

laujok

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Messages
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Re: Jonhson 25 cyl head?

Well today I took the fly wheel off and adjusted trigger coil and power coil distance. OMC Repair manual gives 0.025" distance for power coil from fly wheel. I used duct tape on power coil to get the right gap. Spark check showed that both cylinders have a strong blue spark with a snap. I used 7/16" gap. Everything looks about the same than before.
I didn't test it running today because of lots of rain.
If this motor would have a cracked block, what kind of symptoms would it have?
 
L

laujok

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Joined
Sep 9, 2011
Messages
48
Re: Jonhson 25 cyl head?

Checked exhaust gaskets and baffle plate today, found nothing wrong. Still won't stay running at idle. It revs normally but smokes like hell, just like getting too much gas. The motor was running the last time on last Friday and now when I fired it up it ran totally smooth for the first 10-15 secs. So I was thinking that the motor runs good when the block is dry from water but starts running badly when water pump fills up the block. There was some grey oily residue on top of the baffle plate when I took it off so I think there is still water getting to the cylinders. But WHERE?? Could the block be cracked somewhere where you can't see?

My motor runs almost similar as the motor on this video: http://www.youtube.com/watch?v=n5g1ThqAtIQ&feature=related

But smokes 10 times more...
 
H

Haffiman

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Messages
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Re: Jonhson 25 cyl head?

What is your fuel/oil mix?
Have you tried pulling off the hose from primer solenoid to see if it is leaking fuel when engine is running?
 
L

laujok

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Joined
Sep 9, 2011
Messages
48
Re: Jonhson 25 cyl head?

I just made a fresh mix (50:1) 98 grade fuel and yes, I've tried to isolate the fuel pump and primer but didn't help. When I disconnected the primer hose from intake manifold there was a little bit of fuel spitting out from the brass tube when engine was running. Is that normal or not? The metal clip in the reed plate that sits behind the brass tube is looking all right.

I'm going to make a DVA adapter today so I can measure all my components to make sure that this problem isn't spark related.
 
L

laujok

Seaman Apprentice
Joined
Sep 9, 2011
Messages
48
Re: Jonhson 25 cyl head?

I just made a fresh mix (50:1) 98 grade fuel and yes, I've tried to isolate the fuel pump and primer but didn't help. When I disconnected the primer hose from intake manifold there was a little bit of fuel spitting out from the brass tube when engine was running. Is that normal or not? The metal clip in the reed plate that sits behind the brass tube is looking all right.

I'm going to make a DVA adapter today so I can measure all my components to make sure that this problem isn't spark related.
 
L

laujok

Seaman Apprentice
Joined
Sep 9, 2011
Messages
48
Re: Jonhson 25 cyl head?

I just made a fresh mix (50:1) 98 grade fuel and yes, I've tried to isolate the fuel pump and primer but didn't help. When I disconnected the primer hose from intake manifold there was a little bit of fuel spitting out from the brass tube when engine was running. Is that normal or not? The metal clip in the reed plate that sits behind the brass tube is looking all right.

I'm going to make a DVA adapter today so I can measure all my components to make sure that this problem isn't spark related.
 
L

laujok

Seaman Apprentice
Joined
Sep 9, 2011
Messages
48
Re: Jonhson 25 cyl head?

I just made a fresh mix (50:1) 98 grade fuel and yes, I've tried to isolate the fuel pump and primer but didn't help. When I disconnected the primer hose from intake manifold there was a little bit of fuel spitting out from the brass tube when engine was running. Is that normal or not? The metal clip in the reed plate that sits behind the brass tube is looking all right.

I'm going to make a DVA adapter today so I can measure all my components to make sure that this problem isn't spark related.
 
L

laujok

Seaman Apprentice
Joined
Sep 9, 2011
Messages
48
Re: Jonhson 25 cyl head?

I just made a fresh mix (50:1) 98 grade fuel and yes, I've tried to isolate the fuel pump and primer but didn't help. When I disconnected the primer hose from intake manifold there was a little bit of fuel spitting out from the brass tube when engine was running. Is that normal or not? The metal clip in the reed plate that sits behind the brass tube is looking all right.

I'm going to make a DVA adapter today so I can measure all my components to make sure that this problem isn't spark related.
 
L

laujok

Seaman Apprentice
Joined
Sep 9, 2011
Messages
48
Re: Jonhson 25 cyl head?

I made a DVA adapter and got 200 volts on both orange wires from power pack. I tested the kick back diodes inside the power pack too and they were okay, about 0.55 each (one way). I had the motor running today about 5 minutes and I had to fight to keep it running. I tried with new plugs with the resistor on them (QL77JC4). About 5 minutes of idle and revs lower plug was black and dry and upper was wet. Still runs with the upper disconnected but if I unplug lower it dies immediately.

I'm going to do a leak test tomorrow and check for possible water leaks. Everything else is pretty much checked so far...
 
L

laujok

Seaman Apprentice
Joined
Sep 9, 2011
Messages
48
Re: Jonhson 25 cyl head?

Okay, I tested the block today using Haffimans tips. Didn't see any water entering to the cylinders or crankcase. I tilted the motor up and checked possible water coming out from the exhaust when I had a hose on and there was none. So this mystery still continues...
 
H

Haffiman

Commander
Joined
Dec 17, 2009
Messages
2,454
Re: Jonhson 25 cyl head?

The positive thing, probably ruled out a cracked/leaking block!
Time for a sauna and vodka!
 
A

AlTn

Commander
Joined
Mar 9, 2010
Messages
2,813
Re: Jonhson 25 cyl head?

use your timing light after the motor warms up < 5 minutes at idle? >...is the flash more random on the top cylinder vs. the bottom?..the flash shouldn't be "random " on either, but steady instead
 
L

laujok

Seaman Apprentice
Joined
Sep 9, 2011
Messages
48
Re: Jonhson 25 cyl head?

All right, folks.. I got a 25 hp Yamaha with reasonable price so I'll be having a brake with my OMC's :)

All you have been a great help to me so A BIG THANK YOU for everyone!
 
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