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Topic: 3.0L (120/140) Replacing Your Marine Engine Longblock
Question: How do I replace my damaged longblock with a new or remanufactured product?
Response:
Since the 3.0L engine is not used in automotive applications there aren't enough cores to support a good remanufacturing option. We only supply new longblocks which do not require a core deposit. The other benefit of the new engine is that it includes the new electronic ignition system that GM released in the mid-90's to address several of the ongoing quality issues that plagued this engine over the years.
There are two (2) solutions to this common problem of replacing the 3.0L marine engines, however, there are many factors affecting the final direction to proceed with. Up through 1991, the engine was produced with a two-piece rear main seal and a 12-3/4" flywheel. Then in 1992, the engine was produced with a single piece rear main seal. Finally in the year 2000, GM upgraded to a 14" flywheel which is how the engines are currently being produced.
Solution 1: Marine Engine Repair
- If your existing engine was built before 1992, you will need a 12-3/4" flywheel that matches the two-piece rear main seal, so that you can re-use your existing coupler and starter.
- If your engine was built between 1992 & 2000, you can re-use the flywheel on your existing engine.
- If your engine is not an OMC Cobra engine vintage, it will require that your existing coupler be re-machined to allow it to fit up properly to the 1 pc rear main seal configuration 12-3/4" flywheel. We can help with this as well.
- If your engine was built after 2000 you can use the flywheel that comes with the new or remanufactured longblocks. We have an option for a 12-3/4" flywheel to go on this engine as well.
- If your engine was a large port engine, or the 120 hp built up until 1994, you will also need the exhaust manifold conversion adapter which converts from the old style oval port head to the higher hp rectangular port head, which is the only head being produced today.
- #gm181base (1991 - Current Engines)
Solution 2: Marine Engine Repair
Another option is engine conversion kit that can be used with your existing Mercruiser or OMC Cobra/Volvo SX 3.0L engine. These kits include an engine, flywheel, exhaust manifold gasket, fuel pump, and coupler as a complete kit.
This is a large amount of information to digest and may be a little confusing as these blocks are very hard to come by today, and versus remanufactured products having a new 3.0L longblock is always a better longterm option. In our opinion the best quality option is a new 3.0L straight from GM, which has the 14" flywheel.
Select the following links to view the mentioned products:
New GM Longblock
