Merc 260 - Manifold Riser - Which Gasket to use?

[tvoigt]

Hi, I'm replacing my port side manifold riser. Mercruiser 260, GM 350. Fresh/Raw water cooled (NO heat exchanger). Log style riser. Took the old one off, to find a plate that blocked off the three smaller water jackets. My new riser came with two gaskets, one (open) and one (closed). I'm confused on which setup I should use. Any thoughts? I have photos but having trouble uploading them to here

Your help is appreciated!

 

[Bt Doctur]

If your still using the log style and you have 2 hoses on the manifold and one hose on the riser ,you use the block off plate
With a blockoff plate you can use either gasket ,dosent matter cause its blocked off

 

[LX Kid]

I've got the 305 sm block and this is the way mine is routed and works fine. (Don't use thermostat though.) Maybe yours will be similar.