There can be many reasons, and / or combinations of reasons for engine
vibration. Start with the simplest possible problem, and proceed to the most complicated.
Is your engine
cooled? The 2GM20
is raw water
cooled, a 2GM20F is FW cooled. This does make a difference concerning the correct flexible engine mounts, as the engine is heavier on the starb'd side.
FIRST - how old are the flexible engine mounts? Does the rubber appear collapsed, partially dissolved or liquified, or cracked? Is the rubber still firmly attached to the steel parts
of the mount? Are they genuine Yanmar
mounts, or aftermarket ?
Are the correct Yanmar
mounts installed on the correct side of the engine? As I recall
, this engine model uses 2 different mounts. The mounts look identical, but differ in the shore rating [ measure of rubber firmness] The stiffer mounts are to be installed on the exhaust
manifold side of the engine.
Are the mounts firmly attached to the engine mount brackets? Are the brackets firmly attached to the engine? Are the flex mounts firmly attached to the engine bed