Parasitic Drag? What to call it.

[lots of boats]

Hi.
I want to know what the correct term is for the energy it takes to run the engine operating systems such as the alternater, and on the newer motors like Tohatsu TLDI the air pump, oil pump etc.

These systems use some of the engine's hp to make them work, what is that cost called? Once I get the right term I have some other questions related to how these engines are dyno rated, and whether the energy cost to make them work is linear.

 

[DJ]

Re: Parasitic Drag? What to call it.

You got it. "Parasitic Drag".

However, outboards (since about 1983) are rated at the propeller, so you are getting what the rated HP says it is.

 

[lots of boats]

Re: Parasitic Drag? What to call it.

Thanks,
It didn't seem like the right term. In an aircraft the faster you go the more parasitic drag you get. With a boat engine the faster it turns the more work the onboard systems must do too. I remember when the hp ratings went from flywheel to prop, all of a sudden our 50hp motors were only 40hp. So the next question is about how you rate hp. New posting.

Cheers.

 

[chevyjet]

Re: Parasitic Drag? What to call it.

LOB i think you are on the right track here as far as your TLDI being a dog on the jet, if you take the same size moter and add all this powersucking stuff to it and then expect it to pull like the old one you are bound to be disapointed.

 

[whitewater90]

Re: Parasitic Drag? What to call it.

Lots of Parasitic drag on Tohatsu engines, you ever look at the front of the gearcase? has a 5/16 flat that you are pushing throught the water not to menshion the fact that they are 45 LBs more than a Yamaha, add that up and take into account the big charging system and air pump you have a 70 HP that ways to much.