Grand Banks Marine Engine Drive Train
Learn about the different parts of the drive train and how to replace them.
Keep your boat running smooth and eliminate noise and vibrations
The Grand Banks engine drive train is comprised of a lot of parts that must work in tandem with the engine to provide proper vibration-free power. Running a boat with bad alignment will most likely make all these parts suffer similar fates. This can also cause noises and vibrations which could mistakenly be construed as engine problems.
The basic structural component that transfers thrust from the engines through the propellers starts with the engine stringers. If these are weak or misaligned, you will never get a smooth running boat.
Engine mounts will lose their effectiveness over time as the material that cushions is compressed. This condition is exacerbated over time if the engine is not kept in proper alignment. Once they are spent, it is almost impossible to eliminate vibration from the boat. We seldom use OEM mounts as replacements as for a few dollars more you can get much more durable mounts.
A damaged flex plate can make it difficult to achieve a good alignment. This cause is rare though.
Transmissions that are near failure can cause alignment-like issues. If a boat has had a serious grounding, it’s a good idea to remove the transmission and send it in for a refurbishment by a manufacturer approved rebuild shop.
Theoretically, couplings should last the life of the engine, but once again bad alignment will cause the coupling on the engine and the coupling on the shaft to not mate flatly and distort the faces. Although they can be turned and mated again, it would probably be cheaper to replace them. In some cases there may be an inherent alignment problem in the boat which will cause them to never mate properly. In this case a product like an Aquadrive Coupling can be used to eliminate the vibration and distortion problem.
A bent shaft, usually from a grounding, should always be a prime suspect in any alignment situation.
There are many different styles of stuffing boxes on the various Grand Banks engine drive trains — traditional packed boxes, dripless and water lubricated to mention a few. Of all these the traditional stuffing box will need the most maintenance. Most are packed with wax impregnated material. If the stuffing box is tightened too tight, it will get hot and melt the wax. Over tightening is a mistake many people make. These boxes are meant to drip a bit. If you stop all dripping you have over tightened. In addition you will need to have the packing changed every few years.
Struts can be either bent or warped, depending on the nature of the damage. A grounding can easily damage a strut in most boats. Grand Banks with it’s deep keel is a lot less susceptible to this, but we have seen plenty of damaged struts on Grand Banks and Eastbay Yachts in the yard.
Cutlass bearings do not last forever. They are a rubber product and compress and dry out over time. This is also a situation where running with bad alignment will cause premature failure. Bearing replacement is not a cheap job. Sometimes the drive train has not been taken apart before and parts are just stuck or corroded together. Most of the time we can use our hydraulic press to press the old bearings out, but often have to rely on hacksaw blades and chisels to remove. See the steps on cutlass bearing replacement.
Propellers are the most susceptible to damage because they are mostly unprotected. Hitting bottom or submerged debris can damage props or bend them slightly out of shape. It is best to have them removed from the boat and reconditioned on a regular basis to ensure efficient power from the engine.
Although not directly part of a shaft alignment, rudders not centered properly can cause 0ut-of-alignment symptoms in the yacht. It’s always one of the things that should be checked.