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Dec 30th, 2023
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 Decarbing an outboard
#686009
03/06/06 08:13 PM
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Joined: Jan 2003
Posts: 100
bassntexan
OP
Outdoorsman
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OP
Outdoorsman
Joined: Jan 2003
Posts: 100 |
I've just now heard of doing this. I have access to a boat, 1981 model with a 90hp Johnson. I'd be willing to bet nobody has ever done this. It still runs good, does take some time to get started, but once warm will run all day. Am I just asking for problems if I suggest to the owner that we do this? Is there anything bad that can happen as a result of this?
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Re: Decarbing an outboard
#686010
03/07/06 06:28 PM
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Joined: May 2001
Posts: 162
marbravo
Outdoorsman
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Outdoorsman
Joined: May 2001
Posts: 162 |
I would do a compression test on the engine. If the cylinders are within about 10% compression of each other, it might be a good engine. If they are not all within 10% of each other, decarbing might loosen up the rings, but they may already be cracked or broken and nothing will help the engine. Marbravo
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Re: Decarbing an outboard
#686011
03/07/06 06:30 PM
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Joined: May 2001
Posts: 162
marbravo
Outdoorsman
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Outdoorsman
Joined: May 2001
Posts: 162 |
I would do a compression test on the engine. If the cylinders are within about 10% compression of each other, it might be a good engine. If they are not all within 10% of each other, decarbing might loosen up the rings, but they may already be cracked or broken and nothing will help the engine. Marbravo
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Re: Decarbing an outboard
#686012
03/07/06 07:04 PM
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Joined: Jan 2003
Posts: 100
bassntexan
OP
Outdoorsman
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OP
Outdoorsman
Joined: Jan 2003
Posts: 100 |
Thanks for the reply. Does anyone know of someone in the Austin area that does compression testing? Any idea how much we're looking at paying?
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Re: Decarbing an outboard
#686013
03/07/06 08:11 PM
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Joined: Jul 2001
Posts: 842
KingBingo
Pro Angler
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Pro Angler
Joined: Jul 2001
Posts: 842 |
chris ray is the man! performanceoutboards.com
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Re: Decarbing an outboard
#686014
03/08/06 10:09 PM
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Joined: Dec 2003
Posts: 3,180
2-stroke
TFF Team Angler
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TFF Team Angler
Joined: Dec 2003
Posts: 3,180 |
compression tester about $25.
warm up the engine on the muffs, remove the spark plugs, open the throttle, and test one cylinder at a time by screwing the tester into the spark plug hole and cranking the engine for a couple or three seconds three times.
Some say don't open the throttle, others say only take out the plug of the cylinder you're testing - most say it doesn't matter that much since the most important reading is the difference between cylinders.
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Re: Decarbing an outboard
#686015
03/09/06 01:11 PM
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Joined: May 2001
Posts: 162
marbravo
Outdoorsman
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Outdoorsman
Joined: May 2001
Posts: 162 |
Take out all the plugs, open the throttle full, insert the compression tester in the plug hole and crank the engine until you feel the compression "hit" at least three times. Do it the same way for each cylinder. Compare the readings and determine the difference between cylinders. If the cylinders are within 10% of each other and the difference between the highest and lowest is no more than about 15% (the closer the better), then you have a good engine. If the overall compression is lower than the manufacturers recommended compression, decarboning of the engine may clear that up. Marbravo
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Re: Decarbing an outboard
#686016
03/09/06 03:09 PM
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Joined: Jan 2003
Posts: 100
bassntexan
OP
Outdoorsman
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OP
Outdoorsman
Joined: Jan 2003
Posts: 100 |
Thanks for the info guys. I'll have to head out and by a compression tester. May give it a shot this weekend.
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