Riser block off - closed cooling

[Meast]

I have tried to look for answers but the result has been confusing. Some gaskets have expired and Mercruiser has updated the method. I have Mercruiser 7.4 (454) closed cooling system. 1 piece block off in graphite (27-860231 or 18-8637251) or, 2 pieces block off in graphite (27-860231 or 18-8637251) sandwiched with the stainless steel plate? Sincerely, Magnus

 

[Scott Danforth]

What is your specific question?
Also, if you can yell us the year, or best, a serial number. We can better help you

The 454 has been in boats for over 40 years, so we dont want to guess

 

[Bt Doctur]

2 standard gaskets of your choice, one above and one below the SS plate

 

[HT32BSX115]

I have tried to look for answers but the result has been confusing. Some gaskets have expired and Mercruiser has updated the method. I have Mercruiser 7.4 (454) closed cooling system. 1 piece block off in graphite (27-860231 or 18-8637251) or, 2 pieces block off in graphite (27-860231 or 18-8637251) sandwiched with the stainless steel plate? Sincerely, Magnus

The one piece gasket is simply a stainless steel "plate" (albeit thin enough to be flexible) "coated" with the gasket compound..... that is functionally identical to the separate "plate" sandwiched between 2 gaskets. The plate is necessary to withstand the cooling system pressure of around 15 psi or so.....

I used the single graphite infused plates with my 454 closed cooling system and they work great!

Cheers,

Rick

 

[tpenfield]

I just replaced the gaskets on my 7.4L w/ closed cooling. Merc does not have the stainless steel block-off plate, as they maintain that the new gasket (with internal SS film layer) serves the purpose. Barr still sells the stainless steel plate.

These are the parts I used for each manifold (2 gaskets and 1 plate per)

 

[HT32BSX115]

Merc does not have the stainless steel block-off plate, as they maintain that the new gasket (with internal SS film layer) serves the purpose. Barr still sells the stainless steel plate.

They do work pretty good, although for one reason or another, I did have one leak and had to replace it. I used the old "film" gasket (after scraping the "stuff" from both sides ) with a couple of home made gaskets to pressure check my manifold before re-installing it..

I bolted the riser to the manifold using my home-made block-off gasket plus the studs with gasket sealant while holding the manifold in a vise.

I then pressured up the manifold with compressed air to 20 psi and it held it all day!