25 HP Johnson Boggs down

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shooter26

Petty Officer 3rd Class
Joined
May 31, 2001
Messages
78
Hello everyone.. I have a 1974 25 hp Johnson 25RL74M that boggs down. When I have it opened up for about a minute or 2 it will slow down to idle. Then I turn it down to idle for 30 seconds crank it back up for another minute, over and over. Replaced everything in the fuel system from the Gas tank up to the fuel pump.I've checked the temp. of the water by hand when this happens and it seems to be hot.<br />Thank You for your help. :(
 
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Brian L

Recruit
Joined
Apr 28, 2002
Messages
3
Re: 25 HP Johnson Boggs down

Sure sounds like a fuel problem. Have you rebuilt the carb?
 
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jgmilberg

Cadet
Joined
Apr 28, 2002
Messages
11
Re: 25 HP Johnson Boggs down

I would re-build the carbs first, then start looking at other componants. After the carbs are done if the problem is still there then look at the coils, if they are cracked replace them, the cracks will allow the spark to leak at high speeds under load, this will let the cylinder load up with fuel and carbon. I had the same problem on one of my motors a while back, new coils got me off the dock and back on the water.
 
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seajay

Seaman Apprentice
Joined
Nov 17, 2001
Messages
40
Re: 25 HP Johnson Boggs down

I would try adjusting the air/fuel mixture to insure it is correct the discharge water temp is another issue verify that water pump is operating properly. The high speed jet could have some obstruction remove and clean.
 
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shooter26

Petty Officer 3rd Class
Joined
May 31, 2001
Messages
78
Re: 25 HP Johnson Boggs down

Thanks for the replys. I havent done anything with the carb. I guess I'll start on it. I noticed it's a little wet around the bowl gasket and where the spark plug wires run to the coils? one of the plastic pcs has a couple of hair line cracks in it.any idea of a cost on this stuff.<br />Thanks again for all the help... <br /><br />This board is great!!!
 
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rwise

Captain
Joined
Jul 5, 2001
Messages
3,205
Re: 25 HP Johnson Boggs down

shooter26<br />What about the fuel tank vent, is it open? Is it cloged?<br /><br />Richard
 
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shooter26

Petty Officer 3rd Class
Joined
May 31, 2001
Messages
78
Re: 25 HP Johnson Boggs down

UPDATE.... Replaced a coil, Re-built carb, Had it out over the weekend messed with the low speed (Lean Rich)adjustment.Had it so it would go and not bogg down (Ran Great). Next day started running like crap again (bogging, sneezing).Let it warm up and messed with the adjustment again.It would run good top speed until I would slow down, then I would open it up and it would bogg, I would open and close the throttle in gear (reving it) to get it up to top speed and it would keep running at top speed until I slowed down or it would bogg down and I would rev in gear to get it to go again. Any Ideas?
 
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fireman 757

Petty Officer 1st Class
Joined
May 18, 2002
Messages
276
Re: 25 HP Johnson Boggs down

those ignition coils are only 40 bucks each (just replaced them on three engines). Easy to put on also. Just two 3/8" bolts. Don't forget to put the two wires back under the bolts when you replace them and make sure that the wire clips are secure.
 
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