Johnson GT100 de-carb compression check

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evilwind1

Petty Officer 3rd Class
Joined
Jun 6, 2006
Messages
92
I have a 1988 Johnson GT100 that I ran Seafoam treatment through to see if it would help with compression. I now have 110, 110, 100, 90 and the motor runs much better. I didn't run it on open water ( on boat with load )just through ears. My question now is how long should I run motor before seeing optimum results. I would like to sell this motor as running unit but if the comp. varies to where it could be a problem I will sell for parts or rebuild. Also would like to ask fair price ,any input as to value. Thankyou.
 
S

Solittle

Fleet Admiral
Joined
Apr 28, 2002
Messages
7,518
Re: Johnson GT100 de-carb compression check

My suggestion would be to do the decarb again and this time drop it in the water and run the stuffings out of it. This may clear stuck carbon. Review the decarb procedure before you start.

FYI - I have a 1987 110 hp with numbers of 115 +/- 5. Your 90 is a bit of a stretch.
 
Texasmark

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,560
Re: Johnson GT100 de-carb compression check

You have nothing but a $6 can of Sea Foam to loose and everything to gain. Give it time to do more than it has. Works for me.

Mark
 
M

mcallan

Cadet
Joined
Sep 2, 2006
Messages
18
Re: Johnson GT100 de-carb compression check

Also try johnson/evinrudes enigine tuner, and let it soak for it's full 16 hours.I have noticed great improvements, especially in the triples. Mike
 
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evilwind1

Petty Officer 3rd Class
Joined
Jun 6, 2006
Messages
92
Re: Johnson GT100 de-carb compression check

mcallan said:
Also try johnson/evinrudes enigine tuner, and let it soak for it's full 16 hours.I have noticed great improvements, especially in the triples. Mike
Click to expand...
 
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evilwind1

Petty Officer 3rd Class
Joined
Jun 6, 2006
Messages
92
Re: Johnson GT100 de-carb compression check

Thanks for the info, I just have one more question. I would like to sell this motor , what do you think is a fair price to get, as is ?
 
K

KYHunter2

Chief Petty Officer
Joined
Mar 20, 2006
Messages
512
Re: Johnson GT100 de-carb compression check

Its hard for anyone to place a value on the motor.

Check ebay , and see what a motor of similar age and hp. will bring.

KYHunter
 
Texasmark

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,560
Re: Johnson GT100 de-carb compression check

Your local marine dealer probably has a little black book with 3 prices in it depending upon condition. Might sweet talk him out of the info. Staying local helps keep you in line with local pricing as those books are area sensitive when formulated.

Mark
 
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