I would avoid EFI in a boat for many reasons. You have to use Marine EFI (very expensive), and it doesn't make more power or better economy
If you use an aluminum motor, you need to run a heat exchanger
Use a factory head gasket
Measure the head for flatness with a machinist ground bar.
If it isn't flat, get it machined
If you shave your head, you need to remeasure your push rods
you ran it to 200F. you already spit the head gasket. they spit their head gasket if the temp goes much over 175
best you can do is do a compression test and hope you didnt score the pistons. BTW, these motors have high cranking compression. you should see 170PSI on the gauge.
if you lost...
Im on the 3rd rebuild of a trans because the factory GM (JMBX) torque converters are a joke. only 0.5mm of carbon fiber clutch face bonded and pressed by a hydro-formed piston. they edge load, eat the friction material, take out the pump, which in turn drops pressure and the trans eats itself
Fred on the left is an gator, Barney on the right is a crock
what is missing in the pic is the water moccasin and other reptiles in florida that want to kill you.
If you got a 1996 or later vortec. I would look at a billet aluminum front cover and a custom oil pan. Use the marine accessories from the 1994. Buy manifolds.
If it was me, I would go V8. Same work, same cost, more power
Design life is 15 years
Service life depends on many factors
As for hours, I would expect 3000+ if maintained
Marine motors are usually killed by lack of maintenance, the hardly ever die of old age
Block doesn't care what heads. Only the intake cares
Drive doesn't care what heads, only cares about what flywheel
Main difference between the 1993-1995 motor and the 1996-2003 motor is the heads (and plastic oil pan)
If you get a motor from an s-10. You only get the short block and heads...
Unless the tub is big enough to get the whole drive submerged...... It won't work
Hint, to get the drive submerged, you need to have the boat floating.
Best bet.
Pull the drive
Hook up hose to thermostat housing
Drain when you're done