See full version: Leaking Riser Gasket - DIY Fail
As soon as you get the risers installed, start the engine either in the water or with a flush adapter (muffs) to dry up ( &blow-out) any water left in the cyls, valves and manifolds . As long as you don't let it go with water sitting on top of pistons more than a few days, it won't hurt anything more
All, thanks for the quick and detailed response. To answer your questions Rick, it was fresh water in the risers and the engine is freshwater cooled. I haven't reinstalled the risers yet so I will definitely pull out the flashlight and see if any residual water is in the exhaust chambers as you recommended Ted. Either way, plan will be to proceed as per Rick's advice to pull the plugs and pour in some oil before cranking it to see if any water comes out. [links]
The exhaust manifolds are designed such that they will hold a small amount of water internally to the exhaust chamber before it reaches the exhaust port and valve. Not much water, but a little. You may want to remove the risers again and take your flash light and see if you have water at the bottom of the exhaust chamber. The middle cylinders usually get most of the water that may leak into the exhaust, so #3,5, 4,6 cylinders. Folks who have gasket problems that go unchecked usually find valve damage and loss of compression on those cylinders. [links]
Good advice from Rick and Bondo. I'm not sure that I would pull the manifolds at this point. I'll add some comment about the 454 mercruiser. . . here
Mercruiser OEM V8 SBC 305/5.0L and 350/5.7L Exhaust Manifold and Riser Kit w/ 3 " Spacer
Mercruiser OEM V8 SBC 305/5.0L and 350/5.7L Exhaust Manifold and Riser Kit w/ 6" Spacer
Mercruiser 305/350/377, 5.0/5.7/6.2 Small Block Chevy Exhaust Manifold Assembly (Iron Casting) replaces MerCruiser part # 860246A10
Brand new replacement exhaust manifold kit for 5.0L & 5.7L V8 (Pre-Dry Joint) Mercruiser marine engines, backed by 3 Year Warranty.
•2 Manifolds
•2 Exhaust Elbows/Risers
•2 Elbow mounting Gaskets
•2 Manifold Mounting Gaskets
•Mounting Hardware
•Mercruiser 5.0L 305ci GM Serial # OB525982-OM5999999
•Mercruiser 5.7L 350ci GM Serial # OB525982-OM5999999
5.0l/5.7l Mercruiser Exhaust Manifold And Elbow/riser Kit. 860246a15 807988a03 here
Barr Manifold Exhaust Kit Mercruiser V-8 Dry Joint 5.0-liter And 5.7-liter With more
Barr Manifold Exhaust Kit For Mercruiser V-8 Gm 5.0/5.7-l With 4 Risers And 3 Sp more
Barr Manifold Exhaust Kit For Mercruiser V-6 Dry Joint 4.3-liter With 14anddeg Riser [links]
Barr Manifold Exhaust Kit For Mercruiser V-8 Dry Joint 5.0-liter And 5.7-liter W