I am looking at a boat that claims 1600 horsepower (total) out of twin 3406 engines (no model letter specified)-are they off by about 800 hp? Thanks in advance for your replies-just joined the forum this morning
Well, you can disregard this post, now that I've downloaded the cat specs on the 3406E-it claims 450 to 800bhp. Fuel consumption is going to be a bit high, but I love the engines.
No model number is necessary if you can get the Serial Numbers for the engines. The specification can be found from the Serial Numbers as well as the factory dyno test results if you're interested. Marine engines of the well-tuned variety can turn out some serious horsepower.
Are they claiming they're stock? or how much did they hotrod it? Which new parts did they change? They get that much HP out of a Dodge truck, for several seconds at least.
Thanks, Nige Thanks, Nige. I will try to get the serial numbers on my next visit
With the Serial Numbers the specification and original BHP can be found. Standard engines seem to vary from 475 to 800 BHP at between 1800 & 2300 RPM. The higher HP engines tend to run at 2300.
You can get big horsepower figures from marine engines because, (a) as Nige said, by increasing the RPM. The same torque at at a higher RPM = higher horsepower. (b) The top horsepower engines are rated for intermittent duty only, and (c) you have virtually unlimited cooling available.
The unlimited cooling is the big thing. Marine engines can be fueled very highly; land equipment engines have to be fueled to survive in the worst conditions of high temperatures and altitude. Marine engines worst conditions are cold cooling water, cool charge air, and sea level altitudes... cool charge air from cold water charge air heat exchangers.
From my time in the USN marine engine are rated differently. As I recall main propulsion engines run at a really light duty cycle so those figures are peak horsepower and maybe for 20% at peak over the life cycle of the engine. A truck engine might be a 50% and a generator might be 70 to 90 %. My figure are examples only so don't hold me to the letter on them. The basic issue is a marine engine with the correct pitch screw only pulls high horse power when in an acceleration event. You can put high pitch propellers on and make the hull skip across the waves but your load factor goes up along with fuel usage and engine life goes down.
Cat marine propulsion engines are rated A to E. A = unrestricted continuous - 100% rated load and speed 24 hrs a day - eg. bottom trawlers or tug boats B = heavy duty - rated load and speed 80% - 10 of 12hrs - eg. ferries, crew boats C = Maximum continuous - rated load and speed 50% - 6 of 12 hrs - eg. harbor tugs, fishing boats D = Intermittent Duty - rated load and speed 16% - 2 of 12 hrs - eg. police boats, customs boats E = High Performance - rated load and speed 8% - 1 of 12 hrs - pleasure boats, some patrol boats So yes 800 hp out of 3406 is possible but it will be in the E rating therefore it should only be at that for 8% of the time - eg getting on plane As for fuel consumption is get ugly fast in the high hp range. For example a C18 propulsion engine at its lowest A rated hp is 454 bhp and uses 22.6 US g/hr. Now that same C18 at its highest E rating is 1136 bhp using 59.4 US g/hr !!!
Don't forget constant load, it's a huge factor compared to a truck engine or say a dozer engine. For the most part marine engines only run at high loads when there's room to run a long ways so relatively constant load and speed. Not like a dozer where the rpm is constantly changing all day. But yeah, keeping it all cool is undoubtedly the main factor. I remember asking a CAT service manager once what the upper limit was on horsepower for the 3208's. He replied that the twin turbo marine versions could do 425 horse without breaking a sweat. I told him "Not with me standing near it" but I guess they must have held together they were popular.
IIRC the accessory load is different in the ratings as well - marine does not include any of the accessories (water pump, alternator, etc) whereas automotive use does so part of the difference is simply the power lost to the fan, pumps, etc on the truck engine.
How could I find the fuel consumption for an engine using the serial number?
If you are referring to a Cat engine then post the engine Serial Number here.