As long as the water outlet from the riser is smaller in area than the water inlet area, the system will become pressurized and threreby filled completely.

BT

OHhh Ok, so the spacer wil be getting some water from the riser? The riser has open water jackets at the flange like the merc does? I wonder why they did that?

I suppose as long as it is getting water then it should be OK.

Yes, the the spacer will definitely be getting water from the riser above, so it's not like it's a "dry hot zone". Also like Blue Thunder said, the outlet is smaller than the hose inlet and the four water jackets combined, so the system will have to be pressurized. I didn't think of that but it makes perfect sense. I'm reasonably mechanically inclined and I really don't think it's going to be an issue, especially considering that other people are running the same system with no problems.

I actually kind of like the idea of no water jackets in the manifolds, as stated above, it further secures the inability of water to leak back down into the cylinders.

I'm stiill going to call Eddie Marine but I think it's going to be okay. As far as hose length goes, I'll just get the threaded couplings I need, then go buy the hose and double hose clamp it in place. Should work fine.

Pic of EMI 3" spacer.
http://www.offshoreonly.com/forums/a...d=113237&stc=1

Looks exactly what Roehr's machined for me, except the corners are rounded. Thanks for posting that picture.

I've got a closed cooling system and 3" risers on my 454 engines. There is a solid stainless steel plate between he gaskets that seperate the spacers from the manifold and the riser. It seems like the spacer then isn't getting any cooling water because the coolant circulates in the manifold and the raw water exits thru the riser--that's totally isolated from either water source.

For whatever the reason the spacer never seems unreasonbly warmer than the manifold or the riser...

Check out the plumbing and parts on BAM's website to verify the solid gasket plate.

Poorsche

Poorsche, thanks for the info. Any chance you have BAM's website address handy?

www.mercruiserparts.com is site--here is link that shows a solid blockoff plate for different manifold riser--but same principal---http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=817442%2090&ivar=images/CRUISER/817442.90/25A.png&inbr=1608&bnbr=13&bdesc=EXHAUST+MANIFOLD%2 FELBOW -- another pic at http://www.engines1.com/images/barr/pg63.jpg

Def talk to Mark Berman at mercruiserparts.com--great guy and absolute straight shooter on this stuff

Poorsche