Newbie with tunnel hull project

[HANNlBAL_KING]

I finally got my hands on the RC boat that my dad got for me almost 20 years ago. My stepmother wouldn't let me have it when he passed away in 2001 and my brother finally got it back for me. This obviously has sentimental value so I would like to completely restore it. My goal is to make this a good looking boat that is fast, fun and reliable. All out speed is somewhat important, but not having to worry about the boat going up in flames due to mismatched equipment is paramount.

I've been doing a bit of research and trying to learn as much as I can over this past week, but need a little help when choosing a few things.

First of all, I plan on converting the boat to electric so I will need a new outboard lower unit. I am looking at getting one of the following, but would like some thoughts on which is better and why. I like the thought of not having an adapter if purchasing the second one listed, but I can't seem to find much information comparing the two products or anyone talking about the second one. the OS unit seems to be pretty popular though.

O.S. Outboard Unit Assembly 21XM V2 Outboard

Outboard lower unit

If there are any other lower units I should be considering please feel free to post up.

Next up is what motor and ESC to go with. I am completely lost in this arena and was curious if anyone has any inputs or advice on where I should start and what things I should be looking for. I found this video on YouTube that was very helpful, but it is a few years old and I assume technology has changed a bit since then.

I want to keep the boat as light as possible so I've weighed it with everything in it, weighed it "empty", and weighed the parts I've removed so I can make sure I don't load it up with too much weight during the conversion.

Also, I think I will need a new canopy top. Does anyone know where I could find one?

Any other tips or advice on setting the boat up in terms of balance or lower unit height / angle would be greatly appreciated!

[HTVboats]

As far as the lower goes I prefer the OS because if its mount adjustments and a superior prop shaft. A simple Hyperformance mount sold by OSE is a bolt on. Not knowing the other lower and it's prop shaft I cannot say good or bad either way. Looks great but if the shaft wears and wobbles in short order then you might as well just get an adapter for the K&B you already have mounted.
The easiest FE would be the AQ 2030 or similar on 4S (UL-1 setup), and a T-120 or T-180 controller which is overkill but you won't burn it easily.
Rather than going into the FE unknowns it would be easier to just stay nitro and resurrect your dads hull with an OS complete outboard. Super reliable and no new rigging to explore. Of all the nitro world that OS is the best thing since the original K&B and outperforms it hands down.
Mic

[HANNlBAL_KING]

That is great feedback! Thank you!

I made some progress over the weekend sanding and doing a bit of reinforcing / adding epoxy around the corners for strength of the rear bulkhead where the motor will mount.
2016-06-04 21.04.03.jpg

I cleaned up and removed most of the servo mounting points that were in place before.
2016-06-04 21.06.23.jpg

I decided to go ahead and start purchasing some of my new equipment as well.

Motor:
Watercooled Brushless Inrunner 3660SL 3180kv

ESC:
Turnigy AquaStar 120A Watercooled ESC w/Programming Card

Battery:
ZIPPY Flightmax 5000mAh 4S1P 30C

Lower unit:
OSE lower unit

TX / RX:
Spektrum 4020W Dx4s Dsmr 4ch Tx W/Sr415

[HTVboats]

You went a bit high on KV's for a 4S setup. 3180 is better suited for 3S. Volts times KV= no load rpm. 14.8 times 3180 will give a no load in the 46,000 rpm range and close to 38,000 actual. Need a X438 or less for prop. A 1600-2100kv would work better on 4S.
Mic

[Tails Up]

I am following your build. I can't offer much advice as I am new to electrics. I have a similar plan with my old fiberglass Dumas Hotshot 3.5 KB. I plan on going with an inboard I believe . You may change my mind though. So keep posting your progress.

[HANNlBAL_KING]

Thanks for the info Mic!

I'm still learning about the battery voltages and motors so that is very helpful.

With you saying it would be better suited to a 3s battery, should I assume that would put my no load rpm at around 35,000 range? How would that affect my prop choice and the speed of the boat? I'm guessing multiple factors come into play when looking at the actual rpm range like the type and weight of the boat along with the prop chosen.

This will be a learning experience for me, but I love data and testing so I will probably be getting a GPS and experimenting with different combos and posting up my results with each.

[HOTWATER]

If I were you I would go with what Mic says on the motor...AquaCraft UL-1 motor. I have been running one in my Vision tunnel for a few years now and is plenty fast enough with the right prop. The prop I am using is a Grim Racer 42x55.

[HTVboats]

4S will be faster but buying a cheap 3S battery to start with you will have an easier time getting setup. Then add speed. You can buy another motor later when you get more familiar with FE equip. I can't tell you all the uses for a 3S, basically 12v battery I have found.
Yes you're no load will be in the 33,000 range and actual will be in the high 20's which will be a better shaft speed to work with. Stay low on props 438-440 to start.
Mic

[HANNlBAL_KING]

Parts are starting to show up :)

[Tails Up]

Looks good, I do like the looks of that outboard. What battery power are you going to use?

[HANNlBAL_KING]

I currently have a 4s battery, but am going to order a 3s to start with. Once I get everything configured I will drop a 4s in and see what happens.

I've been doing some research and learning more about prop selection and I am curious if there is any reason I can't go with a more aggressive prop to bring my RPM under load to a more manageable number? It seems like that would be a good way to get my RPM in the ideal range and still utilize this motor.

[HTVboats]

http://www.offshoreelectrics.com/pro...?prod=leo-3660
Or just buy a correct 4S motor for $53. Which is pretty cheap compared to all the hardware you already y have. Don't waste time and money experimenting and re-inventing the boat. If you choose an over aggressive prop you WILL burn down your ESC and possibly your motor. I take back the 3S solution as it compounds problems for someone new. I was trying to let you use the motor you had but a correct motor is as cost effective as a new battery. More than one solution here, but ultimately the right RPM range will save a lot of headaches.
Mic

[HANNlBAL_KING]

Fair point. ok, so that motor with a 4s battery. What prop would you suggest to use with it? Should I find a water jacket for it to keep it cool?

[HOTWATER]

That motor will be good...yes, get a jacket for it (water IN at the LOWER nipple of the jacket, OUT at the TOP nipple)

ABC/ Grim Racer 42x55 - check Temps after running for a minute or so on your 1st couple runs - watch runtimes!! Should get about 3 1/2 - 4 min if everything stays just warm... - 5.5 - 6mm bullet conectors on esc, batt and motor leads...

Here's some pics of my Vision tunnel converted to FE...you may get some ideas from... http://forums.offshoreelectrics.com/...hp?albumid=365

[HANNlBAL_KING]

Thank you Hotwater and HTVboats for all of your feedback! It is very helpful and greatly appreciated.