I was going along about 4,000 rpm’s on the CT River the driveline went out.  No warning.  I’ve had 3 or 4 other instances with universals binding and blowing apart with my 20’ Aluminum Gator jet.  This is a SD309 AT pump powered by a vortec 350.  Geometry looks fine.  I grease them a couple times a year, doesn’t seem to matter.  I get about 100 hours on them and they go.  This is the first time the frame of the driveline has cracked apart, the other times it was just the universal joints.  I have a refreshed one (pictured) to install.   It isn’t super hard to fix, but it’s annoying that it keeps happening.

I’m in the midst of sorting out the water in oil / cracked head issues on my Chevy Vortec 350. It definitely had water getting into a cylinder or two from head cracks and into the crankcase through a leaking intake gasket. I captured most of it in the puke tank.  One of the exhaust manifold bolts was corroded along its length, and an exhaust flapper valve was missing. Trying to sort through the causes, fallout and red-herrings. I’m wondering if a riser or manifold is leaking. The exhaust manifolds and risers are Marinepower aluminum ones. They have never been apart and the boat is 16 years old. It only sees freshwater and is fresh/raw-water cooled. I always drain the manifolds for the winter freeze. The manifolds are still unbolted from the heads. The ports are black with powdery carbon, no gunking up or water washed look to them. I’ve read a lot of the stories of risers going bad and destroying engines, especially in saltwater with iron risers. Very little is written about these high performance aluminum systems. I bought a pair of gaskets just in case I needed them. They were expensive, about $50 with shipping. I’m not sure if I should pull them apart risking damaging the surfaces and replace the paper gaskets. Any of you have experience with aluminum manifold/riser combos?  Do they need frequent replacing like iron ones if only used in rivers and lakes? Here is a pic of the manifolds/risers.