GM produced 2 different 3.0L model marine engines up through 1994. They were both 3.0L Marine Engine models but had different cylinder heads which is where they got the different performance levels; 120 (large oval port head) and 140 Hp (small rectangular port head). They however do range the ratings on them so you could have one version that was previously rated the other version in previous years. Starting in 1995 all that GM produces is the 140 Hp longblock. The new 3.0L longblocks are offered to be used as a replacement either way for which ever version of the engine that you have.

Since the 3.0L marine engines are not used in automotive applications there aren’t enough cores to support a good remanufacturing option in our opinion. Regarding this particular engine we only supply new longblocks which do not require a core deposit. There are several other benefits in this case with the 3.0L being that this is the exact same engine which is/was used by Mercruiser and Volvo Penta to build their respective products.

Another great benefit with the new longblock is that General Motors began supplying the engine with a new electronic ignition system to address the historical issues this engine suffered with head gaskets failures due to detonation. Therefore with the new 3.0L longblocks you get the new longblock assembly but also the water pump, distributor, coil, ignition module, plugs and plug wires.

If you need more than a longblock you will have to begin looking towards a complete turnkey engine known as a bobtail engine.

Installation Drawings for reviewing specific dimensional differences (open is separate windows)

3.0L (Inline 4 Cylinder) Installation Drawing (Select Link)

Tech Tips (Select Link)

New Longblock Product (Select Link )

Buy the products and parts you need...