With a free boat, comes some problems for sure, but any good backyard mechanic can do this. This is why I had to change my Harmonic Balancer plus an explanation of how they work.
A harmonic balancer (sometimes called crankshaft damper, torsional damper, or vibration damper) is the same thing as a harmonic damper except that the balancer includes a counterweight to externally balance the rotating assembly. The harmonic balancer often serves as a pulley for the accessory drive belts turning the alternator, water pump and other crankshaft driven devices.
Each time a cylinder fires, the force of the combustion is pressed to the crankshaft rod journal. The rod journal deflects in a torsional motion to some degree under this force but harmonic vibrations will result from the torsional motion pressure on the crankshaft.
In some engines, the torsional motion of the crankshaft at certain speeds can synchronize with the harmonic vibrations, causing a resonance. In some cases the resonance may stress the crankshaft to the point of cracking or complete failure.
The harmonic balancer helps minimize torsional crankshaft harmonics and resonance. The damper is composed of two elements: an inertia mass and an energy dissipating element. Most often made of rubber, this element is composed of a synthetic elastomer, a clutch, a spring or fluid. The mass counteracts the torsional crank motions and in concert with the energy dissipating element absorbs the harmonics vibrations.
An OEM damper consists of an outer mass bonded/vulcanized to an inner hub. An aftermarket performance damper consists of a mass which is attached/mounted to a housing (steel, aluminum, titanium, etc.) based on the different types of damper and where the mass is controlled differently. The first three use older technology; First is the liquid type damper which surrounds the mass immersed in the housing which is then bonded or welded together. Second is the o-ring type which surrounds the mass with a number of o-rings as it sits in its housing. Third is the friction type which has clutches and spring acting on the mass inside the outer housing. Fourth is the newest type in which the mass sits over and is attached an elastomer ring which is then attached to the outer housing. The crankshaft and damper together become (in its torsional response) a spring-mass-damper system again which can only occur by the two being interference fit together.
Thanks for watching, stay well, and God Bless.
Dave