5.7L is this head gasket or sticking valve

bolo789

Petty Officer 1st Class
Joined
Aug 26, 2002
Messages
376
hi yall, I am posting on be half of my friend,<br /><br />he just bought a use boat with a 5.7L 260 HORSE POWER MERC. it was siting for a year he is trying to get it start, but it is only turning over it didnt fire up as yet .<br /><br />any the problem is this he did a compression test the result is on one side only one cilinder goes to 150 the other three is about 110 125 100, same thing on the other side only one goes over 156 the lowest on that side is about 90 . he took of the thurmostat housing and there is no thurmostat install. he also put oil in the cilinder doing the test but it did not make much diffrent in reading. some one told him the compression is not going to read good antil he get the engine running.<br /><br />thanks for any info. just trying to help a friend
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: 5.7L is this head gasket or sticking valve

By "Finishing" the compression test, he may be able to determine the problem.<br /><br /> Service Bulletin 97-25 "The rest of the story" on compression tests.
 

jimmythekid

Petty Officer 1st Class
Joined
Sep 21, 2004
Messages
331
Re: 5.7L is this head gasket or sticking valve

that engine should run IF the ignition system is in order, and fuel supply is okay, as far as the low compression in one cylinder, if it sat for a year, it MAY come back up after a few hot/cold cycles, but the engine should at least run with those numbers, albeit poorly. as far as no T-stat, maybe someone took it out due to a head gasket issue????? And thats causing the low compression????? who knows <br />i would check the ign system and fuel supply first
 

bolo789

Petty Officer 1st Class
Joined
Aug 26, 2002
Messages
376
Re: 5.7L is this head gasket or sticking valve

thanks guys for the quick respond he just call to say he got the engine start, he will do another compression test soon, i will keep you guys posted,
 

bolo789

Petty Officer 1st Class
Joined
Aug 26, 2002
Messages
376
Re: 5.7L is this head gasket or sticking valve

from what he stated it was not starting because there was a broken wire in the iginition system. will keep ya posted
 
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