---I heard that Mercury was afraid that supply of automotive blocks was at risk.
I doubt this
When GM was manufacturing long blocks for mercury they would assemble one year's supply of every displacement engine for mercruiser in 48 hours. Serious volume capability
The colloquially known 470 was introduced in the late 70's to fill the option spot left from the GM 3.8L engine that mercruiser determined didn't produce the torque required to push a small runabout efficiently
In house designed with the aforementioned Ford parts the 470 aluminum block and large cylinder displacement met the proper torque to weight ratio for the slew of 17-20 foot runabouts being manufactured
Sea ray (and others) even used twin 470 sterndrive setups for mid size cabin cruisers, 270 AJ, Sundancer, Weekender, etc...
When the 4.3L became the ubiquitous GM V6 option the 470 phased out in the late 80's due to better 4.3L performance, warranty issues, specific parts manufacturered only for the 470 requiring less volume in manufacturing, ease of complete long block built to spec acquisition, etc.
The 470, when sound in operation performs quite well in a 17-20 foot runabout with a quick hole shot and wot speed easily in the mid 40's. Kind of a shame it eventually lost support from mercury but they had to cut their losses and move on
