PLZ Help JUST BOUGT MOTOR W LOW COMPRESSION

Joined
Jul 30, 2003
Messages
6
Can anyone tell me the solution to my new headache - just bought 1996 Mercury Gamefisher 15 HP Outboard Motor and tried to run commpression test on both cylinders - top cylinder reads 100-120 PSI and second reads around 40 - 50 PSI. What should I do? How much will it cost to fix it. I apprecviate all responces.
 
Joined
Jul 30, 2003
Messages
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Re: PLZ Help JUST BOUGT MOTOR W LOW COMPRESSION

Also, forgot to ask, if never done any motor rebuilding on boats or cars - should I even bother to start doing it myself? How long does it take to repair 1 cylinder or should I do both cylinders at the same time?<br />Thanks.
 

JB

Honorary Moderator Emeritus
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Mar 25, 2001
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45,907
Re: PLZ Help JUST BOUGT MOTOR W LOW COMPRESSION

Howdy, Slav.<br /><br />First, do a thorough decarboning. Use SEARCH to find out how to do it.<br /><br />Then check compression again. If the two cylinders are not within 10-15% of each other, get a Repair Manual. http://www.outboardrepairs.com/manuals/ <br />That will tell and show you how to overhaul your powerhead.<br /><br />Then you can decide if you want to do it yourself or get someone else to do it.<br /><br />Good luck. :)
 
Joined
Jul 30, 2003
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Re: PLZ Help JUST BOUGT MOTOR W LOW COMPRESSION

After careful research I figured I should atleast try to decarb the engine - if it doesnt work I sell it, but the other question i have is WHAT DO I USE TO DECARB THE ENGINE?<br />THANKS.
 

roscoe

Supreme Mariner
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Oct 30, 2002
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Re: PLZ Help JUST BOUGT MOTOR W LOW COMPRESSION

Your intent is REMOVE the existing carbon buildup from the cylinders, heads, and rings, a spray decarb solvent product, such as SeaFoam Deep Creep, is needed. Some people use one can per cylinder.<br /><br />Run engine at fast idle, with engine running, slowly spray liberal amount into each carb, its gonna smoke up the place,<br />spray some more for a minute or two, now spray a larger amount into carbs until engine chokes out and stops,<br />remove spark plugs and spray decarb liberally into each cylinder, install the spark plugs, let it soak for 3 to 10 hours. <br />Start the engine and run at medium throttle, or if at the lake, run it at full throttle. It won't hurt to spray some more through the carbs. Run it for atleast 10 minutes to flush the crud out of your engine. Now remove and clean, or replace the spark plugs. <br /><br />It works well to do the spraying, the night before you go to the lake. This way you can let it soak overnight, and really flush it out at the lake.<br /><br />Don't do this in front of the garage door or the house, unless you want it coated with greasy crud.
 

The Marine Doctor

Commander
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Jul 25, 2003
Messages
2,177
Re: PLZ Help JUST BOUGT MOTOR W LOW COMPRESSION

96 15hp Gamefisher should be a Force 15. Sears just used a different name. Pull the head off and see if a ring is broken or if the head gasket is blown.<br /><br />TMD
 

greasemonkeyozi

Petty Officer 1st Class
Joined
Jul 16, 2003
Messages
282
Re: PLZ Help JUST BOUGT MOTOR W LOW COMPRESSION

Hey man, Welcome to owning a boat. Dont let something like that get you down. If your motor does have a sheered piston, dont sell it, fix it. You wont get hardley anything for it if you sell it like is, you dont have to be a rocket scientist to rebuild a motor. Its alot easier than a car, trust me. Just buy a shop manual, find a good clean cool working area, make sure you have proper tools, and a case of beer.<br /> This can be a good learning experiance for you, if you come to a problem, just post a message on here and someone will be glad to assist you.
 
Joined
Jul 30, 2003
Messages
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Re: PLZ Help JUST BOUGT MOTOR W LOW COMPRESSION

thanks for advices, I tried to start the engine,but I for some reason cant do that it speens up runs for a sec or two and stops.... any sugestions?
 
Joined
Jul 30, 2003
Messages
6
Re: PLZ Help JUST BOUGT MOTOR W LOW COMPRESSION

I still cant start that stupid motor so I could start spraying decarb in it - should I maybe try to spray into cylinders through the sparkplug holes and also through the carb and let it soak for a day or so and then try to start, I think I'll puke before I start it trying to pull the cord for a while... LOL
 
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