Hi,
My boat has a MerCruiser 400 TRS in it currently (the owners' manual also calls it a MerCruiser 400 TRS). However, the original bill of sale from 1981 says the boat came with with a Mercruiser Cyclone 400.

I'm trying to figure out if they are the same engine as the engine owner's manual makes no reference to the word "Cyclone".

The reason I'm trying to figure out if a MerCruiser 400 TRS and a MerCruiser Cyclone 400 are the exact same thing, is that I'm trying to figure out if my boat has the original factory installed motor in it or whether it was replaced

Also, if the 400 TRS and the Cyclone 400 are the same thing, anyone know why it's called a Cyclone?

Thanks!

same motor. They were just called 400 cyclones

400 cyclone with TRS, 1980-1986, block code XF.

Cyclone's was just a series of engines merc came out with. They were 400,440,and 460 hp. They had 4 bolt main blocks,aluminum high rise intakes,rectangular port heads,forged crank-rods-pistons,and aluminum roller rockers.The 460 hp model was stroked .25" to give it 482 cu. in.'s and 9.2:1 compression. The others had 8.8:1 compression.

That makes sense. Thanks guys.