Classic 50 Cylinder Block Cover leaking gasket 18-2507-9

[Kevin60181]

Mercury Classic 50, 4 cylinder, Serial # A950272
Leaking near the #1 spark plug, at 11pm when viewing.


Question: Sierra Part # 18-2507-9 pictures only 1 gasket (see attached) but includes 2 gaskets.
Are they both the same gasket as pictured? The one with 4 circles, one for each spark plug.

OK, Now the complete Gasket SET, 18-4353 has 2 similar gaskets pictured.

Bottom center of that picture shows the same one as 18-2507-9 that come with 2 gaskets. ???
Top Left shows a similar gasket, but one hole is elongated for 1 of the park plugs.

Viewing my "CYLINDER BLOCK COVER ASSEMBLY", I need the gasket with the elongated hole for cylinder Number 1.

QUESTION: Does Sierra stock number 18-2507-9 come with one of each gasket?
Or are they Both the same gasket that is wrong for my application?

I sure hate to have to buy the complete set for $70 to get 1 gasket....

Thanks again in advance for any help!

 

[Kevin60181]

No Title

Pictures didn't up load. Trying again....

 

[emckelvy]

Some models of the 50 hp block had the enlongated machined pad at #1 cyl and some didn't. Sierra typically includes extra gaskets in their kit to cover more than one model, when it's more economically feasible for them to do so. Otherwise, they'd have to package 2 or more different gasket kits to cover all models, instead of having a "one-size-fits-all" type of kit. Probably a lot easier for inventory purposes, as well.

Some parts aren't necessarily sold individually, in this case it looks like Sierra sells a 2-pack of the cyl block cover gaskets. I've had this experience buying o-rings where the minimum package quantity was, for example, 5. You'll also see this quite often in water pump kits, where there will be extra o-rings & gaskets, for example.

You can still buy (1) replacement gasket from Mercury, P/N 27-85458, for around $6.50 list. This gasket doesn't have the enlongated #1-cyl hole.

A tip on the gasket replacement, these are 1/4" bolts so go easy on their removal, especially if the motor was a "Salty Dog" or has been run in brackish/alkali water. If so, you may encounter some stuck bolts. Use a propane or MAPP torch to heat up the area and free the bolt. Upon reinstallation, apply a thin coating of Permatex #3 non-hardening aviation-type gasket dressing or waterproof marine grease to the bolt threads. They'll never seize again.

HTH..........ed

 

[Kevin60181]

No Title

After hours of seek and find, I found the right gasket, Sierra 18-2810-9 or 18-2810.
Thanks, good advise on the bolts! .
I also ran a 1/4 20 tap thru all 10 holes, they where filled with rust and gunk from the bolts. I'm also replacing all 10 bolts. They too where rusty and full of gunk. I'll coat the bolts with some anti-seize.
Also noticed that there was NO washers under the bolts. Going to add those also.
The old gasket gave way by the elongated hole. They should make that ring a bit thicker, or make the whole gasket out of rubber.