MRP Miss Bud Prop Recommendations

[JLG627]

I've got an MRP Miss Budweiser twin electric hydro with two 7 turn triple rc car motors hooked up to two RC Hydros Victory 6-14 cell esc's. After doing some serious research I came to the conclusion that I should probably invest in something like the Hughey 2:1 speed gear unit with a setup as hot as what I've got. Is this necessary? If not what size prop(s) should I be running with the factory 1:1 gear ratio? How about with the Hughey gear unit? If anyone out there can help me with this, I would be eternally grateful, as there just aren't any tips out there for a setup like this in this kind of a boat.

JLG627

[eboat]

I had one of those boats last summer
I think in the end you will find it will be easier to just take out the 2 motors and gears and put in one motor and a wire drive so you can adjust the angle at the prop and have more props to choose from
There is not much room to work with inside hull

[JLG627]

eboat:

Thank You for responding. I still need some prop recommendations for the setups I have listed though.

Sincerely,

JLG627

[eboat]

Is your boat still set up like the picture with the straight shaft and red prop ?

[eboat]

I still have the red prop in the picture
I just measured it and it is about a X430 size
The biggest 1/8 shaft octura prop is X435 that will fit unless you make a spacer for inside the bigger props
You should also get a drive dog on the shaft
I think mine just had the nut tighten the prop up to a flat shoulder
It was night and day difference when I took out the 2 motors and put in a single SS1 brushed motor with a m445 prop
I am not sure about the 2 motors you are using as I have never really fooled around with the car stuff
If they run real fast it will not take you long to wear out the plastic gears in the original boat setup
Try the X435 to see what will happen but in the end I think you will find one good motor will be easier than using 2 smaller ones

[JLG627]

Dear eboat:

I've got a 3/16x5/16 standard Octura drive dog and an adapter made from K&S copper tubing to fit standard size Octura props. All the performance electric boating websites that I've visited all give prop recommendations for 2:1 geared drive, so that is why I'm considering using the Hughey .05 speed unit, it is geared 1.95:1. The prop recommendations that all these websites give for a 2:1 geared setup on a hydro are as follows: X447, X447/3, X645, X646, X646/3. I have an
X646/3 from another boat but I have not bought the Hughey gear unit yet. Am I wrong in thinking that the Hughey setup swinging the X646/3 would give me the best top speed? It just seems like the props that they're recommending are outrageously huge for a boat this size!!!

[eboat]

How fast do the motors you have turn with the voltage you are going to use ?
If ( big if) you had say 30,000 rpm and then you go through the gear reduction of 2:1 you will only have 15,000 at the prop
I had about 20,000 and was using X445 so if you are turning slower but with more torque you are going to need a bigger prop than the one I was using so the sugestions you have should be in the ballpark
If you are still using the straight shaft you will not be able to change the angle of the prop in the water . Mine was running almost flat

Try the smallest prop you have on it the way it is and see what happens
Just do not go too far before you bring it back (30seconds) and see how hot things are getting

I think it will lift the back too much and make the front drag

[JLG627]

Thank You for the technical info I know it will come in handy in making my final decision on a setup. The rpm range on my motors is in 55,000 range, VERY HOT!!! So I guess my prop would be turning at 27,500 rpm(no load of course).

JLG627

[eboat]

If they turn that fast then the X445 is going to be on the big side of what you will want to use so you had better start with something smaller

[Ub Hauled]

Can I ask you what made you decide on 2 motors in this hull?
Was it the fact that it has a tranny in there already?
It would be much simpler if you had only one motor in there since there isn't much
room... just a thought.

Thank You for the technical info I know it will come in handy in making my final decision on a setup. The rpm range on my motors is in 55,000 range, VERY HOT!!! So I guess my prop would be turning at 27,500 rpm(no load of course).

JLG627

[domwilson]

They originally come with two "wizard" motors on a 1:1 geared transmission.

I think the original prop was a x431.

[JLG627]

Although I have all the confidence in the world to do it, I don't want to make any MAJOR modifications to this hull if I don't have to because I had this exact boat when I was 13 years old and tried to modify the drive hardware then only to have the hull material crack and split on me. I guess you could say I am very weary of messing with the ABS material. But if this setup does not work out then I will definately give the guys at Fine Design a call and go with a single brushless motor and speed control. The only obsticle I can see there is trying to get a motor mount that is close enough to the angle of the prop shaft because the stock prop shaft is at such a shallow angle to the bottom of the boat. Only time will tell if I have chosen the right setup or not, I can't wait to get everything together so I can run the damn thing!

[Scott T]

JLG,
If you want to stick with the twin car motors, I would definitely get a 2:1 gearbox. Coupled with an X440 or X442 (maybe even an X640), you should see about 40mph, based on some rough calculations. This would be a good starting point. I would not put that 646 on there!

If it was my boat (and I love those MRP Miss Buds!), I would go for a nice 2S2P set up, with a single Feigao 7L motor, or a 4S1P set up with the SV27 motor and ESC. Cheap, easy performance. And I'd buy from OSE rather than FDM.

If you're worried about the floor, there's a heap of guys on here that can describe how to laminate some carbon mat on there to really strengthen it up.

Cheers,
Scott

[JLG627]

Scott T,

Thanks a million for the info, it has definately been a big help!

JLG627

[Ub Hauled]

I have a friend that bought mine and did some nice paint job on it.. it looks great.
I am not sure what his plan is as far as drive and power, but it sure looks much better then when I owned it.
Attached is just a mockup of his boat.