I wonder

I think it may be the Dodge or Chrysler v10 in the first generation of the motor it produced 400 hp and 490 ft lbs of torque which makes this engine very close to the same specs I can imagine a marinized version doing the lower hp with slightly less torque. Chrysler matches the displacement at 8.0 L and the bore at 4.00 the stroke matches too at 3.88 so sounds like a truck motor to me.

from wiki

The Viper V10 is based on the rest of the LA family, and appeared with the Dodge Viper in 1992. It was conceived and prototyped as a Magnum 5.9 with two extra cylinders and a longer stroke of 3.88 in (99 mm).

Originally designed as a truck engine, Lamborghini revamped Dodge's cast-iron block V10 for the Viper by recasting the block and heads in aluminium alloy. Some within Lamborghini felt that the pushrod two-valve design, while adequate for the truck application for which the engine was originally created, was unsuitable for a performance car. However, Chrysler was uncertain about the Viper's production costs and sales potential and so declined to provide the budget for the modification.

The first-generation Viper V10 engine has a displacement of 8.0 L (488 in) and produces 400 hp (298 kW) and 490 lb·ft (664 N·m). The second-generation engine, also displacing 8.0 L, produced 450 hp (336 kW) and 490 lb·ft (664 N·m). The third-generation engine, introduced on the 2003 Viper, has a displacement of 8.3 L (505 in³) and produces 510 hp (380 kW) and 535 lb·ft (725 N·m). On January 8, 2007 Dodge released information at the Detroit Auto Show[citation needed] that the 2008 Dodge Viper engine's output would increase to 600 hp (447 kW) and 560 lb·ft (759 N·m) via a slight displacement increase to 8.4 L (510 in³) and the use of variable valve timing.