Nitro Hammer Dual Outboard conversion

[wheelnut]

Hey guys, This is a new project I am working on. I picked up this Nitro Hammer Hull pretty cheap and it is in great shape. I have already cut off the subsurface drive and sealed the hole. I also recently picked up a Tekin Marine 432M esc fairly cheap that I will be using. It is rated for up to 300 amps and should work fine. The hull has plenty of room for cells so to start off with I will be running it on 12 cells. I ordered and received the Orion V2 12X1 motors. I am getting them installed and wired up. I am going to set it up so each motor gets 8.4v. I will be running two 7 cell packs, so basically each motor will be running on its own 7 cell pack. To accomplish this I think I need to wire the motors in parallel and the batteries in series. Is that correct or is there a better way to do it? I know that if you wire the motors in Parallel each motor will receive half the voltage and if I wire two batteries in series it will double the voltage.
Or I guess I could wire the batteries in parallel and the motors in series. Not really sure if there is any advantages or disadvantages for doing it either way. Someone has said that if the motors are wired in parallel then the batteries have to be wired the same. Is this true? I thought they were seperate circuits and did not need to be the same. Someone please help me out.

[SJFE]

What a kewl build:). If I may... I think your motors are a little to hot. I would try something around 19 turns first. It would cost you less in the long run.

[Eyekandyboats]

i like the look of that OB. i'd do a OB project ( scale) if they were not so bloody expensive
I might as well buy the whole boat and sell the rest of the parts and make money off it

[Quicksilver]

In my villain with the tekin 432m, I did the batteries in series and the motors in series. I figure if you're putting 7.2 in 7.2 is coming out of the esc, or in my case 14.4v went in and 14.4 came out and divided by two. So I would also think parallel in and parallel out should also work. 7.2 in 7.2 out.

One tip with that esc, be careful soldering to those posts, I found it quite difficult, since there's only three posts, I would suggest series on the motors like I did. I didnt think about till I got the esc in front of me.

-batt -motor +battery+motor So if you went parallel,
|---------|------------|

you'd need one wire on the first post two wires on the second post and three wires on the third. That is a bit scary imho.
With the motors in series, its one wire on the first post, one on the second and two on the third. I'm sure you could wire up parallel some way, but think about all the juice trying to go through one post from three wires.

Sounds like a cool project, some day I'm getting some outboards, especially if I see someone successfully make a real fast one.

[Fluid]

A few comments if I may. First, don't count on the "300 amp" rating on the Tekin. It was a very good controller (I had three of them) but don't plan on running more than 75-100 amps thorugh it for very long. That is still a lot of amps.

There are several ways to get the 8.4 volts to the motors...but I believe that is too much voltage. Frankly I'd not go over 7.2 volts to each of those motors. What size props will you be using? There is much more drag in an OB compared to an inboard, and 12 turns on 8.4 volts will burn up soon unless you use small props.

I know that if you wire the motors in Parallel each motor will receive half the voltage and if I wire two batteries in series it will double the voltage.

Nope, you have it backwards for the motor. If you wired the the motors in parallel each motor gets the full pack voltage. Like Quicksilver said, wire your packs in series for 16.8 volts, then wire the motors in series so each sees just half tha pack voltage - it is best that way. You have to know what voltage you want at each motor to determine how to wire the motors and packs, it is not interchangeable unless you want to fry your motors or run really slow.

.

[la_zcar]

Be careful with that out drive I found that you need to watch the gear mesh very close on the lower unit and I suggest up grading to bearings if you plan to use it much. You will need to mount the batteries almost at the front of the boat to keep the cg right. I deffinatly agree with SJFE on the 19 turn motor thing. Id suggest using 2 mild 19 turns and a Novak Superduty speed control then just run two 6 cell packs in parrallel.

[SJFE]

The Novak EVX will handle down to 19 turns and is watercooled also. In the event you blow the lower unit gears OSE stocks them. I am planning a build with a set of these OB's next winter. Havent decided on a hull yet.

[wheelnut]

:)

Well, I appreciate the suggestions but, I have already spent over $100.00 on the motors so I am not changing them before I try them. I also already knew better than to trust the amp rating of the esc, but I was guessing that it was a max amp burst rating. The Tekin should handle this setup, we will see.
I will be using the stock props to start.
I will also test it on 12 cells to start.
I will wire the batteries in series and the motors in series.
I am going to the LHS to pick up a long double servo horn. I called and the longest one they have is about 2.5". I was trying to get the motors as far apart as possible. Any ideas on how far apart they should be would be helpfull. I do have other servo horns. I will be running the motors in opposite directions. Meaning the props will be turning the opposite way of each other. Outwards.
Thanks for all the help guys.

[SJFE]

Ok I have to point out somthing. If you run stock prop you will not be able to counter rotate them. You need to pick up a set of counter rotating props.

[SJFE]

I guess these would work... I am unsure of the shaft size.
Product ID: grp-2317.40L
Graupner K Series 40L
Product ID: grp-2317.40
Graupner K Series 40mm

[wheelnut]

Ok I have to point out somthing. If you run stock prop you will not be able to counter rotate them. You need to pick up a set of counter rotating props.

Good point. I did know that, but I wasn't thinking.
Would I really need to run counter rotating props? you think?

['83 chevy]

Good point. I did know that, but I wasn't thinking.
Would I really need to run counter rotating props? you think?

it might want to twist with the props, but not as much as it would be with inboards because of the way the motors are mounted

[SJFE]

Yes. You will get torque roll and it will not track straight. It's not a big deal to get the props.

[wheelnut]

I guess these would work... I am unsure of the shaft size.
Product ID: grp-2317.40L
Graupner K Series 40L
Product ID: grp-2317.40
Graupner K Series 40mm

The upgrade prop I used on one of these when it was on my profisherman was a Octura x632. So it has a 1/8" shaft. Keep in mind that there is very little clearance between the prop and the fin thing on the foot of the outboard. I could probably go one more mm larger. So what props do you think I should use?

[SJFE]

Ask Steven...He will know..I don't own any of them yet.