yes, I am new, I have an aquacraft mini thunder and just tried it with a lipo, it seems to slow down and rev up a lot now. it's almost like the prop comes out of the water or something. My question is- Is my problem due to the lack of weight in the rear? the lipo i am using is just a small 1100mah, it is considerably lighter than the nimh that comes with it. should I add weight to the rear to keep the prop down?

I know its probably newbie stuff, but I am honestly not sure how to correct the problem. Any Ideas? what is this called? If it helps, I let off and get back on it and it goes fine but it cuts down alot.

Any info at all?

Hi mate can you not move some of the weight thats allready in the boat further back?

battery is already all the way back and everything else is mounted. Is this the problem?

If the only problem is that the boat is porpoising (hopping in the water) then yes, work on your center of gravity and weight.

If it came with NIMH and you switched to LIPO, is there a low voltage warning that maybe you're hitting? I checked the manual, they don't make mention of it - just that a 7.2 volt battery is recommended. If you're using a lipo without a low-voltage cutoff, you are might run the battery to a level that it can't be recharged.

Is there any way to adjust your prop depth? Maybe it needs to be lowered?

I am positive it's not the lipo, it seems to be a balance type issue, it is not porpoising, but the prop revs up and seems to be out of the water and the boat slows because the prop is not moving any water. It is almost like it gets a bunch of air trapped under it or something.

Can you post a couple of pics of the back of the boat showing the driveline depth & angle & the prop?

Sounds to me like the prop is cavatating. Try lowering the strut ( if you can ) a little bit. If the strut can`t be lowered, you might have to make a cavatation plate and mount it to the transom. I had one of my boats do this, and the plate took care of the problem untill the hull got up on plane. After that, the boat had enough speed that the prop could get a good bite in the water.

cavatating sounds like my problem! the prop angle is fixed on this one, can you show me an example of a plate?

Hi
I took a look at the boat. The prop is angled down at a fairly steep angle. This is a problem with any hydro and a fixed angled down prop shaft. With the lipo cells and more power ,you have changed the ballance. The least attractive solution is to add weight to the rear. You could test this easily by tapeing weight on the top outside of the hull. Add more as needed to acheive what kind of ride you want. If this works ,you can easily find a way to add that same amt. of weight to the inside.Perhaps make it removeable for future changes. A prop change to one of less lift may help but, that prop angle is going to give a lot of lift no matter what prop you use. A change of prop angle is the best solution and also the hardest to do . This requires a lot of work and I suggest you try the weights first.
n.h.schmidt

Thanks, will do! Also, does anyone else have these boats? it seems to be fairly poor quality, I have had it for 2 weeks and already the stock battery came unsoldered, the steering servo quit, and the radio has broken on me twice! other than that, when it works, I am fairly happy. Am I expecting too much for a beginner boat, or did I just get a lemon?

The servo quited, but did water ever got into the boat ? How did the radio quited ? Simply lost control ?
Check your battery, make sure it is not tightly binded by the holder and the batteries should be allowed to move
back and forth a bit. If any battery is binded by the holder, then sometime the connections between the batteries may be losted
causing the radio to turn off unexpectly.

I have one that did not have the same problem as you described; however, the Thunder is not terribly fast and trying to hop it up is not easy due to the limiting space inside the hull, and as someone pointed out that the angle of the prop is sloped down at a steep angle, making the hop up difficult and too much effort. The MiniRio and MiniV are much better boats in similar class of boat for speed and handling.