671 GM big horse power.

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Wow ...480 HP @ 2500 revs...……..
…………………..Billy...…………………...

I cant imagine their life been very long at this rating
Im pretty sure this is the maximum rating for electronic 671 from the factory

Paul

Something I have never fully understood, the difference between marine propulsion horsepower ratings and the ratings for a identically specced automotive application. Even allowing for the higher RPM settings of the former, that sounds like a bit over the top. But then the US Navy we’re getting some ridiculous figures out of the Cummins 903 (as well as ridiculous RPM) even in N/A forms in some of their landing crafts. Maybe had something to do with either the resistance of water, the expected shorter life expectancy of the military use or they simply rated them differently. Years ago marine applications were often quoted as SHAFT HP, always seemed to be higher.
Even a twin turbo 903, best I ever read was around 375 Hp @ 3000 RPM. for truck use.Some naval specs almost doubled that. But, then those advertised photos and figures in the ad look like a bog standard item, so what would I know?

I don't know anything about the above mentioned motors but i do know that a lot of people, manufacturers and hot rodders included, quote a horsepower figure with the engine in peak tune, on a test bench, with no accessories such as pumps, fans, clutch, alternator, etc. This gives a much higher reading than horsepower "at the wheels."

I think it is a bit like we used to say when Japanese trucks came on to the market:- they were designed to carry "little Japanese tons" not our usual British, European or American tons.

Horsepower is just one particular named measure of the rate of doing work. It is defined to be 745.7 watts. There are others.

Brake horsepower simply refers to the way that horsepower is measured. That is typically done using a machine called an Dynamometer which in one form or another uses a brake to constrain the engine’s output.

The dynamometer measures the braking effort and that gives an estimate of the torque the engine is producing and given the rpm, it also yields the rate at which the engine is doing work. That is, it gives you a measurement of the engine’s power. Scale that appropriately and it comes out as Horsepower, or Kilowatts, or whatever unit you like.

There are qualifiers for the measurement methodology. The SAE Gross standard is based on an engine running without its fan, water pump, air filter and full exhaust (gross HP). The SAE Net and European PS standards are run with all of those parts installed as they would be in a car (net HP). Power can also be measured through the drive line as installed in the vehicle using a chassis dynamometer. Those measurements will be uniformly lower because of driveline losses.

I have a fantastic manual produced by GM Detroit called Marine Library.

It gives every engine they made (except that supersonic one mentioned above) in the 53/71/92 series with relationship to boats. It has pages on working out boat hull dimensions and prop sizes and pitches to achieve the best result.

More importantly it it gives all the standard variations on each engine to achieve the aim. Basically the only difference is bigger injectors and higher rpm - only bolt on stuff different, no internal changes.

The 6-71 M and N are rated at 185 BHP (bare engine) 174 SHP (with accessories)@ 1,800 rpm with N55 injectors and 265BHP (240SHP)@ 2,300rpm with N70 injectors and 280BHP (257 SHP) @ 2.300 with N80 injectors.

The most interesting one is the 6-V53

It ranges from the basic 100SHP @ 2,400RPM with N40 Injectors right through 7 progressively more powerful engines just boosted by injector size until we reach the 6V-53T. Same engine but @ 2,800RPM with N70 Injectors and turbo-boost giving 292SHP. In other words they tripled the power just by stuffing more fuel and air into it!

Lang

Squirrely AD, says for 1 engine then both engines for sale.
My take is they are 240 HP each and they are quoting it as a package at 480 HP.
Cheers Steve.

No. Looks like he is right. Some beaut Screamer noise here!

.

24 gal - 100 litres per hour!

At one time I was going to build a "Prony Brake", I think that is what it is called. It uses a friction pad to be applied against say the flywheel of an old engine and the arm is pivoted and a counter balance weight is used as well. Then out with the calculator and with known RPM and weights and diameter you can work out the HP.
Way beyond me at the moment so the idea never got off the ground.

That plate says M 95 squirters and that is for a 450 hp job.
Guessing that the 485 hp will be larger again
………………..Billy...………………..