trolling motor verses small petrol motor.

[jurgenscraft]

trolling motor verses small petrol motor.

is there any way that the output of trolling motors quoted in pounds thrust can be equated in HP. I think that the thrust stated in trolling motor specifications is measured at the propellor,( actual pushing power ) and HP> is measured at the flywheel of the petrol motor. What I am trying to find out is how much thrust can be delivered by a 5 hp motor that I want to use as a trolling motor. Kind Regards William Wright

 

[Silvertip]

Re: trolling motor verses small petrol motor.

Re: trolling motor verses small petrol motor.

Outboard horsepower is currently measured at the prop, not the flywheel. HP and thrust are two different values. Push against your house wall with 50 pounds of pressure and that equates to 50 pounds of thrust pushing your boat. A 5 HP outboard will develop far more than 50# of thrust. How much is a function of prop diameter and pitch. You really have two problems to consider. #1 is which type of motor do you want (gas or electric). #2 is how much power you actually need. If you slow troll hour-after-hour you would be better off with a petrol engine. If you position fish, a bow-mount electric is probably better.

 

[--GQ--]

Re: trolling motor verses small petrol motor.

Re: trolling motor verses small petrol motor.

There is no set rule or standard to compare Horse power to Thrust. They are two different types of measurement. H.P. is a constant measurement where Thrust is a variable measurement defined by many factors.

The ability of an object(boat) to move through a medium(water) can be measured in term of thrust. Basically Thrust is the same as the unit Force which is defined by MASS times ACCELERATION. To find the accurate Thrust(force) exerted by an object(trolling motor), it has to be in motion. Thrust by nature is a "conditioned" measurement.

Horse power on the other hand is a relative constant in a sense that it is not defined by the type of medium in which an object travel. Horse Power can be converted into Thrust through gearing mechanism, but the amount of Horse Power doesn't necessary predict the amount of Thrust output because again it is a variable.

Case and point. NASA tested different engines of varying Thrust at different altitude. The H.P conversion variation was huge thus making it useless in any comparison. P=FxD/T

In my opinion, you are better off converting the electrical rating of your trolling Motor into Watts and compare it to H.P. rating. Which is 746 watts/H.P. Also consider the motor efficiency factor. In general 90% is pretty good. So 90% of the motor V A rating is the number to use.

Note: Most manufactures provide a comprehensive motor data sheet with the manual. You will find the efficiency factor there.

In summary Thrust and Horse Power are types of measurement used to measure Force and Power but they are not the same.Kinda like comparing apples and oranges. They're both fruits.

Speaking of fruits; most Iboats members are fruits but some of us have more seeds if you get my drift. 8)8)8).