HOTTZU98

I have seen 454 mag carb engines advertised as 350hp? Is this the 385hp engines prop HP?? The 1999 7.4l Is 310hp isnt it? So my question is does the 7.4L EFI make 310hp at the prop or is that crankshaft HP?

SkiDoc

The 454 mag carb is 365 at the prop. 454 mag efi is 385 at the prop. Not sure about the 7.4, but I believe is 310 at the prop.

East Coast B

The 7.4 carb is 300 at prop, 7.4 mpi is 310. 7.4 mag carb is 350 at prop, 7.4 mag mpi is 385 at prop. Here is a link to the engine list specifications. It doesn't list the 7.4mpi for some reason, but does list the LX which was only around for a short period. I had the 7.4mpi(not LX) and it was 310hp at prop. I forget what year it was, but it's been many years, that engines hp rating was changed from the crank to the propshaft.

http://www.outdrives.com/merc/sternspecs.html

East Coast B

7.4L MPI Sterndrive Specifications

Propshaft Horsepower: 310 (232 kW)
Displacement (Liter/CID): 7.4/454
Cylinders: V-8
Bore & Stroke (in/mm): 4.25 x 4.00/108 x 101
Compression Ratio: 8.9:1
Fuel System: MPI
Full Throttle RPM Range: 4200-4600
Ignition Type: Digital
Alternator: 65/917
Length (in/cm): 39/99
Width (in/cm): 32/82
Height (in/cm): 22/56
Weight (lbs/kg) - Alpha: N/A
Weight (lbs/kg) - Bravo One: 1158/525
Weight (lbs/kg) - Bravo Two: 1170/531
Weight (lbs/kg) - Bravo Three: 1179/535
Gear Ratio - Alpha Drive (primary/optional/high altitude): N/A
Gear Ratio - Bravo One (primary/optional/high altitude): 1.5/1.36/1.65
Gear Ratio - Bravo Two (primary/optional/high altitude): 2.0/1.81/2.2
Gear Ratio - Bravo Three (primary/optional/high altude): 2.0/1.81/2.2

East Coast B

I just ran into a guy with a 1990 454mag and it had 365hp on the carb cover label. Is that 365hp at the prop or on the crank?? My 94 454mag carb listed at the site above and in my seloc mercruiser manual lists me at 350hp. Where is the 365hp rated at? I know there was a change from listing hp on the crank to the prop, when did that occur?

Pat McPherson

The Gen V 454mag carb was rated 365 at the prop, and the Gen VI 454mag carb was 350HP at the prop. Gen VI 454MagMPI, 385 at the prop.

The Gen VI 7.4MPI (L-29 engine) was rated 310HP at the prop, 340 at the crank.

East Coast B

What year did they start the gen VI 454mag carb? My 454 mag carb is a 1994 and I didn't think they started the gen VI many years later.

East Coast B

Is there something in the engine serial number that states what gen it is?

Pat McPherson

Gen VI engines started in 1996.
They have roller cams and the easiest way to tell is by the timing chain cover. The cover is cast not sheet metal and has only 6 bolts.