What prop for my setup on 3s?

[boilo56]

Hi my boat is a Pursuit. The ESC is Turnigy marine 180 amps. the motor is a 3974-2200kv. I wish to run it on 3s 500mah 40c, only for sport. What prop would give me some speed, a good runtime(5 - 6 minutes would be good) without to much heat. I plan on running this for FPV driving.

Thanks for your advices!

[Jamey]

On paper 2200kv on 3s is about equivelent to 1650kv on 4s. Or very close to the stock SSS motor if that helps you any. What prop did you like with the stock motor on 4s?

[kevinpratt823]

Maybe start with old faithful,- a x442, and see how it goes.

[boilo56]

On paper 2200kv on 3s is about equivelent to 1650kv on 4s. Or very close to the stock SSS motor if that helps you any. What prop did you like with the stock motor on 4s?

I liked the Grimracer 42x55, and the x442.

[785boats]

boilo56.
If the revs with your 3s set up are about the same as the original 1650kv motor on 4s & you use the same size prop, you will have a higher current draw for the same boat speed. The same number of watts are required to spin that prop to that same speed & Ohms Law dictates that because of the lower voltage the current must be higher.
Therefore your run times will be lower with the same capacity battery. You will need to run a couple of packs in parallel.

I assume that is a typo in your first post, & you meant to type 5000mah not '500'mah.

[boilo56]

boilo56.
If the revs with your 3s set up are about the same as the original 1650kv motor on 4s & you use the same size prop, you will have a higher current draw for the same boat speed. The same number of watts are required to spin that prop to that same speed & Ohms Law dictates that because of the lower voltage the current must be higher.
Therefore your run times will be lower with the same capacity battery. You will need to run a couple of packs in parallel.

I assume that is a typo in your first post, & you meant to type 5000mah not '500'mah.

So i can run 3s x442 with 2 3s packs in parallel. Yes it was typo, 5000mah is the right number. Now another question, what about temps? With higher amp draw, i'm guessing the heat will also go up?

[Jamey]

The amp draw will be higher than the stock motor on 4s but the stock motor is a smaller 3660. Your larger motor should easily be able to handle the same prop and higher amp draw without getting hot. One of the most common Pursuit set ups is a 2200kv 40xx motor on 4s with a 45mm prop. Without changing kv, dropping down to 3s is going to drop the amp draw just as long as the boat still airs out good at the slower top speeds. In other words you will be running more conservative a setup as most. I personally would start with the x442 and move on to the m445 likely. Let us know how you like it. I have a feeling you will be asking about props for 4s very soon

[boilo56]

Can you tell me what is the difference between ''x'' props and ''m'' props?

[Jamey]

The m series basically has less "tongue". That is the portion of the leading edge of the blade closest to the hub. It extends out as the first part that hits the water as the prop rotates. Compare the octura x442 to the stock pursuit prop in that area and you will see what I am referring to. Picture the M series sort of half way between the stock and x. There are some prop diagrams in this forum that will help too. On paper the x should give a little better low speed bite. I am sure that depends on the size and application.

You go from the x442 to the m445 because it would normally draw less amps and is easier to turn than an unmodified x445.

[boilo56]

Thanks for the info! i appreciate! I am building up my prop box, i'll check to buy one m445 to add to the collection!

[zooma]

I have a box-stock HK Pursuit. I have stayed with the stock 1620kv motor and four cells. I have propped up from an M445 to M545. Went from 37 to 41 MPH. So, assuming the 2200kv on 3s is equivalent, you might use an M545 too. On the other hand, it may be uncomfortably fast for FPV.

Note, that I had to replace the two-piece shaft with an OSE one-piece part, in order to get an Octura prop to fit at the end. Before that, I was able to fit a Prather B220 prop to fit the stock shaft. A little slower, but got me in the water quicker. Stock prop was a dud, even on 4 cells.

BTW - I have the 3974-2200kv on the shelf for a later date.

[Jamey]

Very mixed reviews on the stock Pursuit prop. I felt the same as you about it, just never would bite and push the boat. Too much ventilation to get up on step but still no speed once there. Going from the stock prop to the octura x440/3 and x442 was like night and day. Both of these props fit on the original two-piece shaft by the way.

[boilo56]

Very mixed reviews on the stock Pursuit prop. I felt the same as you about it, just never would bite and push the boat. Too much ventilation to get up on step but still no speed once there. Going from the stock prop to the octura x440/3 and x442 was like night and day. Both of these props fit on the original two-piece shaft by the way.

Well, i can say the stock prop on the Pursuit is more on the ''learn-to-run'' side... But on 5s, that prop is not doing bad, in fact, i think this boat is meant to run 5s on the stock setup! I did sharpenned and polish the stock prop, and we'll see how it is going tomorrow!

[boilo56]

Here are some pictures of my stock prop.IMG_20150626_212924.jpgIMG_20150627_092717.jpgIMG_20150627_092731.jpgIMG_20150627_092750.jpg

[martin]

The stock prop has a low blade area ( detongued & backcut ) also with a low pitch. It is a 43mm diameter x 1.2 pitch ratio = 51.6mm pitch or 2.03" pitch, as a comparison an x442 is 42mm diameter with a 1.4 pitch ratio = 58.8mm pitch or 2.31" pitch which will also have less slip with the extra blade area as well as more pitch for higher speed over the stock prop.