View Full Version : Mini Cat Racing Micro Hydro help

06-29-2007, 08:00 PM
Just got this and installed everything. Battery is mounted on the left side of the motor mount and esc is on the other side. Receiver is towards the back. I noticed until it got up on plane it almost looks like its sinking. The front dips into the water...enough to make me nervous(its my first real boat besides the mini-v) Is this normal for hydros or is something off.

It also cavitates a good amount. Once its on plane its freaking awesome but im afraid of it taking on water and going under. After 10 minutes of running I noticed a few spoonfulls of water inside the hull. Im planning on putting a sponge or two in to help soak it up but is this normal? Its not coming in through the tape, the hatch is sealed very well.

Any tips and help is greatly appreciated. I want to run it tomorrow but dont want to risk loosing such a cool boat. Thanks.


06-29-2007, 08:13 PM
James are you taping up the hatch?

06-29-2007, 08:20 PM
whenevr i see hydros speeding up from a stop, the front end does look like its about to submarine and they do cavitate a little bit, but when they do get up to speed they run good...i think this is because the CoG of hydros are more up front than with other boats........although, im not exactly sure this is normal, i see it happen alot w/ hydros, so im guessing it is....

as for the water, it could be coming in from the drivshaft or maybe there could be a small leak in the watercooling....

06-29-2007, 08:27 PM
Im taping up the hatch well. Taking my time making sure the tape is all the way down. Ill take off the fuel line and test it all to see if thats it. I put the boat in my bath tub and didnt notice any water coming in. Maybe there is a tiny crack where the hull is joined together? I ran for a good ten minutes and their wasnt too much water like I said. Enough to make me worry. The last thing I want is to short out my electronics when im no where near shore. Ill check those and report back. I took video of it so I will upload that shortly....maybe it will give you a better understanding of the cavitation.

06-29-2007, 08:30 PM
Make sure the drive cable is greased good. preshure test the cooling system...Be sure the water jacket is not leaking.

06-29-2007, 09:26 PM
I tested the water cooling system and all seems fine. No leaks.

I filled up my bath tub and submerged the rear end of the boat. I was holding it vertical and submerged the whole rear end(prop, steering linkage, rudder, antenna mount) up to where the rear hatch tapes shut. After about 30 seconds I noticed some water. It looks like if water is seeping in from the rightmost rear bottom...where the back of the boat meets the bottom of the hull. ---I dont really see how though. It doesnt look cracked or anything. Clear coat looks fine. I added some 5 minute epoxy in that corrner and around where the driveshaft is epoxied just to make sure. Im going to stick it in water again in a bit and see if it stopped. I sure hob thats what it was.

06-29-2007, 09:43 PM
Get a flash light and shine it through the hull....It will give you a better look.

06-29-2007, 09:58 PM
It seems that seeping in the back right was it. I submerged it again and no water. I then let it float for a bit and then pushed down to submerge the whole boat all around(obviously not all the way up to the hatch opening as it was open).

NO WATER inside!! Nice! im planning on putting the receiver in a ballon and bringing the battery towards the back more to alter the CG. I watched two vids of this boat on the page where its for sale and neither of them do what mine is doing. They pretty much get up and go from the start.

Can anybody tell me what happens if I bring the prop up or drop it down more? Thanks :)

06-29-2007, 10:38 PM
although moving the batts might help solve the problem, the ideal CoG of a hydro would be a little bit behind the transom of the sponsons....althogh you did say once it gets up and going it runs great, i would probably leave it as it is...although adjusting the strut angle might help it from almost submarining when speeding up, it might have negative effects on your performance once you are up to speed...

06-30-2007, 12:35 AM
Here is the video guys:


You can clearly see what I mean by cavitation and the front sinking in every now and then. The two vids ive seen of these, neither of them do this. They just get up and go! Its clearly got to be related to the prop depth and cg but im not sure what to start with first. Im assuming its cavitating alot because the front wants to dip in pulling the rear of the boat out of the water.

You can see in the video that it is a fast boat and small....damn small! Hull is cramped for space but its very nice.

The only real complaint I have is the fact that there seemed to be a leak in the hull. Hopefully the small leak I found was the only leak. I guess I will find out tomorrow.

I was having a blast running it. Once on plane it just straight up rips, the pond I ran on is realativly small too.

The ending of the video is pretty funny. When its only my second boat, and my gf flipped my mini-v earlier that day and shorted it all out, and the hydro suddenly cuts out in the middle of the pond I sure got nervous:)

06-30-2007, 02:43 AM
The water going over the front is normal, next the hydro is not designed to turn left, right turn only! when getting going from a stop just punch it, and avoid any rudder movements as this can prevent the boat from getting on plane. The cavatation can also be normal due to a high rpm motor/ small prop. If you use a ballon over the receiver make sure you remove it when your done running as it cause condesation inside the ballon/receiver.

thats a sweet boat, to small for my tastes though!!!!! ENJOY:D

06-30-2007, 09:07 AM
I know its right turn only. But it turns left at moderate speeds well. I have spare stock 27mm props and I also picked up a package of 30mm props. What type of difference might I see switching out to the 30mm?

What can I lube the drive cable with? Im looking for something I can pick up around me(maybe at home depot or something similar) There is a boat place near me would they have anything?

06-30-2007, 11:57 AM
I just changed the prop and realized that it had a 30mm on it stock. Im switching out to the 27mm to see if that helps anything. Ive lubed the drive cable with some Team Losi clear grease that comes with their vehicles. When I removed the cable there seemed to be some water droplets on it. How thick can the grease be that I put on the cable. I dont want to create alot of friction but I dont want to use light stuff if its not going to do anything.

06-30-2007, 08:37 PM
Just got back from the pond.

With the 27mm prop it cavitates ALOT MORE. I could hardly get it up on plane. I put the battery more towards the rear and that helped alot. I put the 30mm prop back on and ran like that for a battery pack. Once the lipo cutoff kicked in I brought it in and checked for water. There still was some. not as much, maybe like a teaspoon or so. I put a piece of sponge in the rear and it was damp so that helped a bit. My guess is its coming in from the driveshaft.

Should I put some thick grease on it to help stop it from coming in?

06-30-2007, 08:53 PM
some cable grease or think grease woulf work good to keep out water....

07-01-2007, 12:00 AM
Why don't you just give it a toss when you launch it? Also, brushless systems where ment to run WOT all the time. hammer it buddy! Coming on and off plane constantly is gonna draw more amps and create more heat. IMO.

Thats a cool boat. I kinda want one. If there are 10MPH winds or so, can you still run it? Kinda looks like it just might blow over...............

07-01-2007, 09:52 AM
Ive had no problems running it like I am. The esc/motor have never been over 100 degrees. They lipo is around 111 or so. It turns tighter to the left than the right. I have to set up the linkage better. Its a fun little boat, definitly worth the price.

07-01-2007, 07:14 PM
Did you say the ESC has battery cutoff? What voltage does the ESC cutoff at? I may pick one of these up to play around with on nice calm weather days.

Doug Smock
07-01-2007, 10:19 PM
The instructions say to lubricate these with a mixture of STP and light oil. It sounds to me like the CG is too far forward. The correct CG is 6.1" from the transom. About even with the aft end of the motor. Not the typical 1" behind the sponson transoms. We have a few at the club and none of them stay completely dry.
Hope this helps

07-02-2007, 09:40 PM
Thanks Doug. What exactly is STP(dont mean to sound stupid)? I just got my Maxamps 11.1v 1550mah lipo and its alot smaller than the ones i was using. Once I changed the CG back it performed better. Im going to try some grease on the driveshaft to see if that helps. I think i might need to go a bit bigger on the prop to help stop the cavitation.

'83 chevy
07-02-2007, 09:54 PM
What exactly is STP

its a brand of oil and other car liquid products

07-02-2007, 09:58 PM
I remembered it as being an oil treatment (http://www.stp.com/products.html). Not an oil.

07-02-2007, 11:19 PM
I remembered it as being an oil treatment (http://www.stp.com/products.html). Not an oil.

Thats what I thought too:confused: It seems like they make that and fuel stabilizer or something.

Doug Smock
07-02-2007, 11:33 PM
Thats what I thought too:confused: It seems like they make that and fuel stabilizer or something.

It's real thick, thats why they want you to mix it with light oil. Seems like alot to go through huh?
I think I would try some of the silicone brake grease that you can get at the auto parts store. The stuff I have used in the past is pretty good and it's not as thick as the Prather grease.

Let us know how you make out.:)