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.

Does the engine have an oil pressure sensor / sender unit like this?  They can leak quarts in minutes under throttle.

First thing you need to do is swap out that carb for a marine certified carb.  It is unsafe and illegal to run that.  That Holley 3310-2 is a great carb, but not worth burning up for.  I like the Marine Demons (now part of Holley) because of the fuel sights on the carb bowls and the built-in quick change secondary spring housing.  To cover a lean bog the previous advice is good.  I also include a 50cc accelerator pump and playing with different sized pump squirters to help cover the lean bog.  If you plan on playing with the carb you really need to get accustomed to reading spark plugs.  The proper set up will yield snappy acceleration with brownish plugs.  NGK copper plugs read the best, stainless not at all.  Readings must be taken by shutting down quickly after a full throttle run.  It is a fine dance between tuning jetting, power valve(s), accelerator pumps, secondary springs, float levels, initial and total timing, plug heat range, engine temp,  and fuel octane.   The goal is to run near the edge but backed-off enough to ensure longevity.  It is possible that the impeller clearance is too great causing increased rpm's or the and/or the tach reading is correct.

You didn't say if your cam is a flat-tappet or conventional hydraulic.  You need additional zinc during break-in on non-roller cams, then I use Mobil1 15-50 synthetic. 
Advantages of synthetics include less carbon deposits in cylinders and throughout the engine, less wear, and longer oil change intervals.  Mobil1 advantage is its wide availability at stores lite Walmart and Autozone and reasonable price, $22.88 per 5 quart jug.  Disadvantages of synthetics are the higher price and they leak more from engine seals and gasket gaps as the engines wear.  The conventional Dino-oils clog up over-clearances so you have less "sweating" and drips of oil.  Many good oils out there to choose from.  My engines usually die from breakage rather than wear!  I change it once or twice a season, whenever it looses its transparency and darkens up. My boat engine consumes oil from all the sustained hour+ runs at 4,500 rpms while bouncing in 1-3' waves.  I add a quart every 5-10 hours or so of run time.  My spark plugs never foul with Mobil1.  I have a mild Chevy Vortec 350 with a carb.  My set-up also has dual oil filters, and of course I use Mobil1 filters.  I also use mobil1 red grease on my jet pump. Happy shopping.

I took my choke out years ago and just left the hole alone.  No apparent ill effects.  I suppose you could silicone it closed or put a tiny piece of gorilla tape over the hole on the bottom side if it worries you.

I have the same set up in a different boat.  Need more info...Where are you seeing bubbles?  Does the nozzle trim up and down fully with the boat on the trailer?  There is a physical limit on the trim range where the nozzle pieces make contact, is it close to that in its articulation?  The trim motor should move from full down to full up position in about 5 seconds.  If it is much slower then it may be an electrical issue such as a weak charging system, battery or bad diodes in the trim control circuit.  Is the trim pump reservoir full?  Is there a chance that the reservoir might have been submerged?  Water will make the fluid frothy and it won't hold the force necessary to keep the trim up under throttle.  These units self bleed provided there is enough fluid in the reservoir (almost to the top), the nuts are tight and there is no water in it.  I just realized the word "trim" may confuse newbies here.  On inboard and outboard engines they call the tilting effect "power trim".  These "diverters" are really power trims and use the same hydraulic pumps as inboard and outboard engines.

When all is working right it should resemble this:


Or this:

On a clockwise engine pcv valve goes on the right because oil is slung up on the left side by the crank.  Breather in the back left for cross flow.  This one has an improvised "puke can" detour on the PCV hose.  It is a Craftsman water trap for an air compressor.

And the winner is...

Make sure it isn't just leaking down from the valve cover / breather if equipped.  If it is oil leaking out the head gasket on a performance engine you are likely on borrowed time.  You can seal it with Permatex black or JB Weld.  Clean it well with brake-clean beforehand.  You of course run the risk of blowing a head gasket leading to more costly repairs.  Maybe a good time to pull the heads and freshen them up.  If you do the grunt work yourself it should cost less than $1,000.