1996 Mercury 25 compression spec?

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Bowhunter1661
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Location: Chicago Suburbs, Illinois

1996 Mercury 25 compression spec?

Post by Bowhunter1661 »

Just curious if anyone knows the spec for these motors. This motor has the chrome cylinder bores as well, not standard steel. I am looking to buy the motor from a guy in Missouri but when he tested it on came back at 91 on bottom and 97 on top (This was cold and not oiled). I have tested a few motors in the past and almost all were in the 120 range. I have no experience with chrome lined bores not sure if they need to be hot or oiled..

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Skiffing
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Location: Northern Massachusetts

1996 Mercury 25 compression spec?

Post by Skiffing »

I'm not surprised by those low readings. The test was done incorrectly.

According to the 1996 merc manual for 25 hp 2 cycle max compression is 180 psi. Minimum is 127 psi. Below 120 indicates problems. No more than 15% difference between cylinders.

This manual is on boatinfo.no

Procedure:

Run engine until thermostat opens.

Remove all plugs. Hit kill switch.

Install gauge.

Open throttle plate to WOT and crank. Stop when highest reading is achieved.

Rinse and repeat.

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Bowhunter1661
Posts: 212
Joined: 05 Sep 2012, 18:43
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Location: Chicago Suburbs, Illinois

1996 Mercury 25 compression spec?

Post by Bowhunter1661 »

Excellent, that is exactly what I needed. Does anyone know anything about there motors? Are they decent? Last awhile? Not too sure about the coated aluminum cylinders on these motors..

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jethro
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Location: Henniker, NH

1996 Mercury 25 compression spec?

Post by jethro »

My boat has a '95 and I don't think it has the nickel cyl bores but regardless it's been a fantastic motor. Flawless so far, many, many hours of trolling.
I fish, therefore, I am.

1993 Starcraft SF 14 DLX side console with 25 hp Mercury 2 stroke
2003 Sylvan 2100 Profish walkthrough with 150 Mercury Saltwater and 6hp Mecury 4 stroke kicker

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