Help with an outboard.

[kendt]

I am trying to piece together an outboard to push a 35"tunnel. I have a 4074 size motor on the way so I assume I would need a 7.5 cc lower unit to fit it on. Is a 4074 enough power for a tunnel that size and what would be the best choice for a lower unit. Would the proboat outboard work, k&b, hyper bullet drive.

I need all the help I can get
Thanks

[ron1950]

a OS lower unit wood be enough with a ul 1 motor or even bigger motor ....the boat in my avatar is 29 inches and runs low 50's so take your pick

[Make-a-Wake]

I'd use a 4082..............

[rcboatmanwithkids2880]

Hi Guy's ,

Have you seen this motor from Hobbyking.com Turnigy 56-74-1050 ( see attachment ) , it was pointed out to me by a guy on this site named Lohring . Seems like a perfect BL Motor for an outboard of over 32 inched long that will be powered by 6S + , seriously considering it for my current tunnel project . Good to see Turnigy coming out with good BL Motors at a reasonable price ....

All the best in F/E R/C Boating ,

Brad

[HTVboats]

Three important questions. What KV is your 4074? How heavy is your 35"hull? Are you sport running or looking for a competative race setup?
Best bang for the buck on a lower would be a used K&B .45 or new Hyperformance .45 size lower. Will hold up and handle well. A 35" is .45 size hull and light would be under 4 lbs. bare hull and heavy over 6 lbs. I have a 1400KV Leopard 4074 that pushes my .45 size hull 9lbs total weight in the water. With a M445 on 5S speeds are in the high 40's maybe low 50's. 6S definate 50's. If you have an 1800kv you could go 4-5S and a 2000-2200kv I would stay with a 4S. My 1600KV 4082 on 5S definately pushed my boat into the 50's and with 6S could be really fast.
Going down in KV's to the 1100-1300 range on 6s you could probably pull more prop but speeds will be similar.
Mic

[kendt]

The hull would be a hot shot .45 FG. Im not sure yet what the weight will be since i am just in the process of aquiring the hull. The 4072 is also a 1400kv. I will be running only for fun and shooting for a 6s set up. I have done some inquiring about a 7.5 lower end. MACOA doesnt seem to answer messages or even respond to online orders. The os unit is way too expensive to get all the pieces. If I cant get a k&b unit I may go with the 7.5 bullet drive.

[Darin Jordan]

The Bullet Drives are pretty nice, especially for the price. For that kind of power, the smallish .150 flex cable on the 3.5 sized units is not going to hold up. They are just barely adequate for our current P power systems... You'll want the beefier flex assembly, and for a boat that size, the 7.5 is more appropriate. The boat is likely also designed to HANDLE with a 7.5 unit, which has considerably different geometry compared to a 3.5 of the same manufacture...

[kendt]

Thanks for that. I hadn't thought of the shaft size/ strength. Glad I didnt drop the dough for the os parts.

[HTVboats]

I have run that 1400kv motor on 6S and you will get all the power the HotShot can handle and then some. MECOA just isn't what a suplier should be. For K&B stuff I rely on the 4sale section of International Waters or E-bay. Nothing wrong with the Hyperformance unit and their adapter is a bolt on setup. Props that should work are either an X442,M445 or Grimracer 42X66,44X66. or 45X68. Hope to see you report a successful build.
Mic

[kendt]

Thanks for the info on props. Glad to here I didnt buy a dud for a motor. I'm hopeing to make the hull into a more scale version of boat with a driver and an interior like pleasure boat style of tunnel. That will all depend on how the batteries and stuff fit in the hull.I will def be posting the progress of the build.

[kendt]

Ok I finally hear back from MECAO, They dont have 7.5 lower units and wont for several months. How can a company stay in business like that.Oh well fortunately there are other options.