Mariner 1985-6 80 hp bad compression

[rajawolf]

Hi, <br />I have a 1985-86 Mariner 80 HP 4 cylinder inline serial #A8053922<br />This motor has been in the garage for 3 years now, and before this the motor was running fine.<br />I wanted to get back into fishing so bought the boat out of storage, and decided to do a compression check on the cylinders prior to firing the motor up, results below.<br />#1 105<br />#2 35 (shock horror)<br />#3 100<br />#4 this cylinder is hard to get to without a flex screw-in connector for the gauge, so just put the finger over the plug hole for now and it blows hard.<br /><br />Can anybody help with suggestions why #2 is bad?<br /><br />Thank you <br />Tony

 

[WillyBWright]

Re: Mariner 1985-6 80 hp bad compression

Welcome to iboats.<br /><br />That motor can seem to run just fine with one cylinder with low compression, maybe a little smoother. But there will be a lack of full horsepower. The compression was probably bad in #2 before you stored. But I would run it and treat it with a decarbonizer and hope for the best before tearing into it. Johnnyrude offers Engine Tuner. Merc sells the same stuff but their cans say Power Tune. Both products work well, instructions are on the can. I've also heard of using SeaFoam although I can't personally vouch for it's effectiveness ... never tried it.<br /><br />For more information regarding decarbonizing...<br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=36;t=000006 <br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=36;t=000016

 

[rajawolf]

Re: Mariner 1985-6 80 hp bad compression

thank you WillyBWright <br /> <br />i will give that a go.

 

[rajawolf]

Re: Mariner 1985-6 80 hp bad compression

Hi again..<br /><br />looks like i need to rebuild this motor..more so now i am not buying a new one until next year.<br /><br />Manual which one?<br />Mercury/Mariner Outboard Tune-Up & Repair Manual <br />Mercury Outboards, 40-115hp, 3-4 Cyl. 1965-1989 <br />Seloc<br /><br />Also anybody from Australia (Gold Coast) who can tell me where i can purchase one, I think ordering from this site this close to xmas may take too long, or maybe not, can anybody help me with this please.<br /><br />Thank you<br />Tony

 

[rajawolf]

Re: Mariner 1985-6 80 hp bad compression

Hi,<br /> I have removed the powerhead, and do not like what i see already, can you please tell me if this motor is now un-repairable. below is URL to pics of motor.<br />Thank you <br />Tony<br /><br /> http://home.swiftdsl.com.au/~dwayne/1a.JPG <br /> http://home.swiftdsl.com.au/~dwayne/2b.JPG