# relation of Engine HP to RPM

Discussion in 'Propulsion' started by majaregielou, Mar 12, 2013.

1. Joined: Mar 2013
Posts: 10
Likes: 0, Points: 0, Legacy Rep: 10
Location: United Arab Emirates

### majaregielouJunior Member

how can we relate the engine's horsepower to its rpm? without any given torque.. is there any formula for this? thanks and kind regards.

2. Joined: May 2004
Posts: 5,372
Likes: 256, Points: 93, Legacy Rep: 3380
Location: Italy (Garda Lake) and Croatia (Istria)

### daiquiriEngineering and Design

3. Joined: Oct 2008
Posts: 7,519
Likes: 1,408, Points: 113, Legacy Rep: 2488
Location: Japan

### Ad HocNaval Architect

4. Joined: Sep 2008
Posts: 721
Likes: 11, Points: 0, Legacy Rep: 57
Location: Great Lakes

### jonrSenior Member

In general, smaller engines can rotate at higher rpms without flying apart.

5. Joined: Oct 2007
Posts: 2,936
Likes: 148, Points: 63, Legacy Rep: 1593
Location: Arlington, WA-USA

### PetrosSenior Member

horsepower is the rate at which it holds a given torque. You have no hp without torque.

hp is in direct relationship to both torque and rpm, you can not related it to rpm only without reference to a torque value.

6. Joined: May 2009
Posts: 664
Likes: 113, Points: 43, Legacy Rep: 447
Location: Landlocked...

### YellowjacketSenior Member

hp = T x RPM / 5252

For each given hp and rpm there is a corresponding torque.

7. Joined: Aug 2002
Posts: 16,397
Likes: 1,432, Points: 123, Legacy Rep: 2031
Location: Milwaukee, WI

### gonzoSenior Member

The formula shows that at 5252 RPM HP=torque in ft/lbs

8. ### Submarine TomPrevious Member

Simply by looking at it's RPM to hp curve (graph).

9. Joined: Aug 2002
Posts: 16,397
Likes: 1,432, Points: 123, Legacy Rep: 2031
Location: Milwaukee, WI

### gonzoSenior Member

I think that it pretty much it. Otherwise, torque and RPM are the two variables in the formula for HP.

Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.