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Yanmar Pleasure Boat Marine Engine Help
Overview - Flexible Engine Mounts
Firstly, let us make sure we understand that, working from the bottom up, the engine beds, the flexible engine mounts and the engine mount brackets, are separate identities. When installing a new engine please take into account that you can:
You SHOULD NOT, however, modify the engine mount brackets (the pieces of metal that stick out from the engine that sit on the flexible mounts) so that the distance from the center of the crankshaft to the mounting hole is different from that supplied.
The selection and position of flexible mounts is important for effective dampening.
Flexible engine mounts supplied as Yanmar accessories and listed in the original Yanmar brochure and in the parts books as optional parts, are extensively assessed and tested by Yanmar before they are included as a Yanmar part. In my experience, these mounts, fitted as originally intended, are a perfect match for the engine.
Sometimes a customer will complain that the engine mounts are too soft, here's why they are as they are:
If the mounts are replaced with stiffer mounts the peak amplitude, as shown on the graph on the right, moves further to the right, above the idle RPM. Vibration becomes very noticable. If your boat vibrates while coming into a bay or the dock, the engine mounts may be too stiff (or faulty, the idle rpm is set too low, the engine is not aligned correctly, the prop is crook, the shaft is bent, etc.). Do not operate the engine in this rpm range until the problem is fixed as the engine may eventually fail. Also, you can see from the peak amplitude point on the diagram that the engine really bounces around as it comes to a stop. This is normal.
Offshore safety tie
This drawing is for GM, HM, JH and LH series engines.
This drawing is for LY and CX engines. The bottom table has the dimensions for these mounts.
On all models, try and keep the engine foot or bracket closer to lower end of dimension 'H' if possible.