Low Compression in 1999 25hp mercury

salty jack

Recruit
Joined
Sep 19, 2003
Messages
3
my well maintained ,low hours {65} 25 hp Merc started to idle rough,took it to merc mechanic who tested compression ,only 65psi in top and 55psi in bottom,what can the problem be. motor regularly serviced,never overheated.Suggestions please, motor still runs well at speed.
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,821
Re: Low Compression in 1999 25hp mercury

It could be the mechanic doesn't know how to properly check the compression, or is trying to make the engine look bad so he can make money off of you.<br /><br />You may just have a carb problem or an ignition problem.<br /><br />I would get a second mechanic to look at it.
 

The Marine Doctor

Commander
Joined
Jul 25, 2003
Messages
2,177
Re: Low Compression in 1999 25hp mercury

With numbers like that I would suspect that maybe it was run without oil, overheated or run lean on the top end.<br /><br />But it is always best to get a second opinion.<br /><br />TMD
 

werdna

Seaman
Joined
Sep 9, 2003
Messages
57
Re: Low Compression in 1999 25hp mercury

Agreed. Where abouts in Aus are you? if you're in Perth i can reccommend to you a fantasic mechanic who's been doing all of our motors for as long as i can remember. email me wrighta@vesta.curtin.edu.au if you like
 

salty jack

Recruit
Joined
Sep 19, 2003
Messages
3
Re: Low Compression in 1999 25hp mercury

Thanks guys,I am in Cairns at the moment on a fishing safari amonst the big barra at the top end,so as you can see they{mechanics} have really got me by the short and Curliesand I have been really particular about fuel and oil
 

salty jack

Recruit
Joined
Sep 19, 2003
Messages
3
Re: Low Compression in 1999 25hp mercury

Just thought of something, had to remove motor from the boat and travel 800k's over very rugged terrain with the motor lashed down in the bottom of the boat, would that have stuffed anything up?
 

The Marine Doctor

Commander
Joined
Jul 25, 2003
Messages
2,177
Re: Low Compression in 1999 25hp mercury

Those engines are tough...some bouncing around would probebly not hurt it. You could though check for loose wires.<br /><br />TMD
 
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