89 100hp Mariner compression test

utfyrfytr

Petty Officer 2nd Class
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Jul 14, 2014
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Going to do a compression check on an 89 100hp Mariner this AM. I understand those are the 2+2 motors and I was wondering if there is anything different about compression checking those as compared to a standard motor. I am not familiar with this system so I was just wondering.
 

flyingscott

Fleet Admiral
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Apr 8, 2014
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No difference just pull the kill switch lanyard to kill the spark and do the test. The 2+2 system is in controlled by the carbs only the ignition still fires all 4 plugs.
 

utfyrfytr

Petty Officer 2nd Class
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Jul 14, 2014
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185
Thanks for the reply. What is the thought behind the 2+2 system, is it less fuel and more economical to run or something else?
 

racerone

Supreme Mariner
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Dec 28, 2013
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The lower 2 carburetors only allow a wee bit of fuel in at idle.----That is for cooling and lubrication.-------For those who often idle for some time it is a fuel saving idea.
 

utfyrfytr

Petty Officer 2nd Class
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Jul 14, 2014
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Sorry, I keep coming up with questions the more I learn. Is this a system that is still in use or was this kind of a fad thing for a few years and then replaced with something else? Was it dependable or a mechanics (and owners) nightmare? Thanks
 

flyingscott

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Apr 8, 2014
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That system was used for close to 15 yrs. It allows for a pretty good idle and saves fuel. I had the 125 version and it is still one of my favorite motors. They are finicky and a factory service manual is a must have. They were only nightmares for people who had no clue how to take care of them or mechanics who were unfamiliar with them.
 

racerone

Supreme Mariner
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Dec 28, 2013
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It is a very simple concept !!!---Just not well understood like many outboard concepts !
 
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