I keep hearing how bad the one piece units were, but I used 3 sets over many years of salt water boating, much more severe conditions than any fresh water boaters face and I NEVER once had any problems with them. The originals were 14 years old (they started in freshwater, and wound up in salt), the 2nd set I ran 6 years and the third has 3 on them. Never a hydrolock, never water in the oil. NO gasket to fail between the riser and manifold.
If I was putting a new set of manifolds on now, I'd like to see if I could adapt the Merc dry joint system to this engine. Its one of their better ideas....
Ayuh,.... I guess you just plain ole been Lucky all these years Lou,....
The problem was core-shiftin' durin' the castin' process, 'n thin walls in places,....
They can just all of a sudden dump water into the motor, hydro-lockin', 'n bendin' rods,...
I personally know 3 times they destroyed 4.3l motors by runnin' 'em,....
2 of which were the same guy, 1 set of OMC, 'n then rebuilt his motor, 'n used a set of Merc batwings, 'n Blew that motor,...
He's now on the 3rd motor, 'n GLM manifold/ risers,...
All in the Sweetwater seas,.....