Re: motor size
They aren't even close to the same kind of engine.
The 3.0L is a GM 4 cylinder engine.
The 3.7 is a Mercruiser only engine with an aluminum block, open deck design, with a Ford 460 head and valve system. It was also noted for having an outboard motor charging system mounted inside the crankshaft pulley.
It failed misserably.
It also had probles with the camshaft wearing a groove in the seal area and allowing antifreeze into the oil. Some used speedy sleeves for a temporary fix till they sold them. The fix is to replace the cam.
Then, if it's old enough and had the 3" heat exchanger it would overheat. This was a bad thing to have happen on an open deck engine. Blows the head gasket every time.
Look for one with a 4" Heat exchanger if you still want a 4.3.
Oh, yeah, Mercruiser stopped making them in 89/90. Many parts are NLA and there are other problems too.
The 3.0L has parts available everywhere.
One note. The reason people like the 3.7 (aka 470's) when they work is because they have a lot more torque an HP than a 3.0L.
