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25 Merc spilt block gasket failure

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tomme boy
Posts: 262
6
Location: 52732

25 Merc spilt block gasket failure

Post by tomme boy »

My 25 Merc has been starting to run really bad at idle. It is also blowing gas out of the side of the block. I was told that this is a common problem with the Merc split case design.

I am going to have to either repair this or get a new motor. Has anyone here done this and how was it? Dealer here want 5 hours min to fix it over winter. He says there is no gasket per say. but just a sealant.

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Pappy
Donor
Posts: 2842
9
Location: Central Florida

25 Merc spilt block gasket failure

Post by Pappy »

Your dealer is correct in that there is no gasket. "Gel Seal" is used to seal the machined surfaces in place of a gasket.
Be prepared to pull the powerhead and remove the front half down to the crank. Flywheel and ignition will have to be removed as well.

turbotodd
Posts: 1177
8
Location: 72032

25 Merc spilt block gasket failure

Post by turbotodd »

5 hours sounds about right if a dealer's doing it. I remember doing a few of those Pieces of junk back in the day. Merc never admitted that there was a problem with them.

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onthewater102
Posts: 2148
5
Location: CT

25 Merc spilt block gasket failure

Post by onthewater102 »

What year models was this an issue on?
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turbotodd
Posts: 1177
8
Location: 72032

25 Merc spilt block gasket failure

Post by turbotodd »

I stepped into the business in '92, and got out of Mercury in 1998 or 9. Don't know what years were affected. Mercosil was also a headache.

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