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-   -   502 with low compression (https://www.offshoreonly.com/forums/general-q/196815-502-low-compression.html)

rmcdade 10-07-2008 07:56 AM

502 with low compression
 
I am looking to buy a 27 fountain and just had a compression test done on it. It’s a 502 mag with 166hrs on it. All the cylinders were around 150 except #5. It was 110. Any ideas on what the cause could be and how much it would be to fix. I know its hard to tell without pulling the motor apart. I am trying to figure out how much to drop my offer that I made him. Should I bail out on the deal?

Thanks
Rob

Ted G 10-07-2008 08:30 AM

With low hours like that I would suspect valve issues due to a failed injector. I tulipped 3 valves on one of mine due to low flow from the injectors. You could have a leakdown test done, that should tell if it's valve issues for sure.

ezstriper 10-07-2008 05:30 PM

you can shoot some reg oil in the cyl and re-ck if it goes up then you have a piston/ring issue(doubtfull though) my bet is a valve..Rob

Smitty 10-07-2008 06:45 PM

Get a leakdown test performed and it will tell you if it is valves or rings and then you can accurately make an offer based on that.

bcfountain 10-07-2008 07:14 PM

low compression
 
my27fountain was the same way when i bought it.it is a 94 502 mpi,mag.it had 395hrs when i bought and 6 was week,[guy let the riser gasket leak].i used that as a barging tool also.knocked off 600 bucks.with few hours on your motor,i would not suppect that issue,but the can leak from the inside out.maybe it got a back wash and hurt a valve.hope this helps

Griswald 10-07-2008 08:35 PM

did it ever get hot?


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