Arminius
Well-Known Member
- Oct 30, 2019
- 1,068
- Boat Info
- Bowrider 200 Select, 2003
- Engines
- 5.0L MPI, 260 hp w/Alpha 1 Drive
I was looking at new boats and giving the 4.3/4.5 a fair shake. Volvo-Penta gets 280 hp out of their marinized GM engine which is 1.07 hp per cube. The 11.5:1 compression ratio on regular is the key. I had it in my XT-5 which produced 1.6 hp per cube. Not much ground clearance but a revolutionary engine. Gossip is a Corvette owner invented reverse cooling to prevent preignition in the heads and left it under seal at a GM garage as he tried to sell the tech. Next morning, he claimed his seals had been broken and a patent fight ensued with GM buying the technology as part of the settlement. I think this is where the 280 hp on regular comes from. The 4.3 remains a stub V-8 with a balance shaft added. Here are the guarded comments on Wiki:
"Commencing with the 2014 model year, a new LV3 EcoTec3 4300, based on GM's GEN V (LT1) Small Block V8, became the new base motor for the next generation Chevrolet Silverado/GMC Sierra light duty trucks, and was phased in throughout the rest of the truck/van line after the 2015 model year. This aluminum block and head design was significantly different to the cast iron block and head engine it replaced, signalling an end to a design dating back to 1955. Like its small block V8 counterparts, GM Powertrain also sells the motor for marine and industrial applications."
As to the secret sauce, Wiki says:
"The aluminum heads also incorporate steam vents to prevent gas pockets from building up in critical areas, and this is vital in allowing the coolant to manage heat build-up for high-performance applications. Such design features allow for a higher compression ratio with no fear of detonation. The thermostat has been located at a low position, which eliminates the possibility of a gas pocket preventing the thermostat from properly sensing the heat of the coolant."
Anyway, having 280 hp in an aluminum V-6 I/O sounds good to me. My big test of my first new boat purchase had me in a wet suit in Lake Union in early spring gauging its pull from on top my slalom ski. I went with the outboard then but this more civilized I/O might pass. A Chapperal maybe.
"Commencing with the 2014 model year, a new LV3 EcoTec3 4300, based on GM's GEN V (LT1) Small Block V8, became the new base motor for the next generation Chevrolet Silverado/GMC Sierra light duty trucks, and was phased in throughout the rest of the truck/van line after the 2015 model year. This aluminum block and head design was significantly different to the cast iron block and head engine it replaced, signalling an end to a design dating back to 1955. Like its small block V8 counterparts, GM Powertrain also sells the motor for marine and industrial applications."
As to the secret sauce, Wiki says:
"The aluminum heads also incorporate steam vents to prevent gas pockets from building up in critical areas, and this is vital in allowing the coolant to manage heat build-up for high-performance applications. Such design features allow for a higher compression ratio with no fear of detonation. The thermostat has been located at a low position, which eliminates the possibility of a gas pocket preventing the thermostat from properly sensing the heat of the coolant."
Anyway, having 280 hp in an aluminum V-6 I/O sounds good to me. My big test of my first new boat purchase had me in a wet suit in Lake Union in early spring gauging its pull from on top my slalom ski. I went with the outboard then but this more civilized I/O might pass. A Chapperal maybe.
