Put my boat back together, but now vibratinnng!!!

[iamandrew]

After waiting for some parts for a while, ive put my Genesis back together, yet there seems to be a fair bit of vibration.
I havent put it back in the water yet, but just gave it a few bursts of power. Sounded normal at low speeds though, and no noise out of the ordinary.
It wasnt vibrating that bad last time I used it though, ive alligned everything again.
Ive also tryed it with no prop and it seems to be doing the same thing.
I put a fair bit of grease in the stuffing tube though
maybe I should just run it and see how it goes!?

[martin]

You need to have load on the prop, Unless their is a problem developed the vibration will stop when you have the boat in the water running with load on the prop.

[iamandrew]

haha yeah, im probably just a bit paranoid there was somthing that i missed. theres no knicks out of the prop or anything and the drive dog all looks fine

[sundog]

After waiting for some parts for a while, ive put my Genesis back together, yet there seems to be a fair bit of vibration.
I havent put it back in the water yet, but just gave it a few bursts of power. Sounded normal at low speeds though, and no noise out of the ordinary.
It wasnt vibrating that bad last time I used it though, ive alligned everything again.
Ive also tryed it with no prop and it seems to be doing the same thing.
I put a fair bit of grease in the stuffing tube though
maybe I should just run it and see how it goes!?

I believe I'd try harder to locate the source of the vibration before I set it in the water. What all did you replace on it?

[iamandrew]

the only thing that i actually "replaced" was a 4mm drive dog. with another 4mm drive dog which is exactly the same size, apart from that, i had removed everything from the boat and put it back together. it looks like the vibration is coming from the strut. I loaded it up with lots of grease but didnt think that could cause it..... not sure what else to check , everythings done up tight and seems like its adjusted to how it was previously due to like screw marks and tiny surface rust :D hehehe

[iamandrew]

well ran the boat, was fine at full speed however it ran very hot.
it even made the wires on my 4074 melt a tiny bit into the plastic mount on the motor... batts got pretty puffed up as well... im going to switch back to the 2 blade prop., maybe the 3 blade was just loading up too much? im not sure, it was okay last time though!

[iamandrew]

would going to 5S on my 2200kv reduce the amps on everything?

[Rumdog]

no. It will only make matters worse.

[sundog]

well ran the boat, was fine at full speed however it ran very hot.
it even made the wires on my 4074 melt a tiny bit into the plastic mount on the motor... batts got pretty puffed up as well... im going to switch back to the 2 blade prop., maybe the 3 blade was just loading up too much? im not sure, it was okay last time though!

Yup, it figures. If it has vibration when out of the water, putting it in the water ain't going to fix it. There's still something amiss. I'd run it (briefly) without the prop, then without the drive dog, then without the prop shaft (if square drive) or flex, etc. working my way back to the motor to see if you can determine what the cause of the vibration is. Vibration is never good. It might seem to disappear at higher RPM's, but as you found - it will just makes things worse.

[iamandrew]

the vibrating was definatly coming from the strut.
its still running the 2 peice flex shaft.
Maybe the drive cup in the strut peice is slightly worn and causing it?

[Rumdog]

I disagree. Simply putting it in the water can and very likely will eliminate the vibration of the driveline. Unless, you have an unbalanced prop. I've built a few cats that had this exact issue. Vibrates on the bench, runs smooth as silk under load.

[martin]

When you run them out of the water with no load on the drive system they will vibrate, When you put them in the water with load going through the drive system & motor your taking any slop for want of a better word out of the drive. I have had many boats that out of the water sound like a bag of nails but soon as their in the water with load their fine. That not to say you shouldnt look for anything that could be loose or out of true.

[sundog]

Yes, I know what you are saying about the water putting a load on the driveline and taking up slop. But loose, out of true, unbalanced, bent, installed incorrectly, worn, etc. isn't 'fixed' just because the vibration sound is deadened somewhat when in water. If something is wrong you need to find the problem and fix it - like iamandrew is discovering. "Put it in the water and run it" was not good advice in his case.

Iamandrew, when you say "everything was done up tight" did you leave a little clearance at the drive dog (easy to spin with fingers) and do you use a teflon/nylon washer? maybe you have some binding there causing the overheating. Packing the strut full of grease is not a problem.

[iamandrew]

I didn't leave much of a gap between the drive dog and the strut,
I do have Teflon washer between them.
I thought that I didn't need to leave much of a gap because when using a 2 piece flex cable its the cable inside the shaft which shortens when the motor loads up.
Ive confirmed with my programming card that I was running the 4074 2200kv at 7.5 timing.
According to most posts on this site I should have been using the 15 timing.
My question is now, should I do away with the 2 piece flex and go for a 4mm one piece, or should i remove the entire thing and use the 3/16th size.

I had very poor run times on the weekend. like 5mins MAX before it shut down into low cutoff.
I used to get a lot more. looks like it loaded up the batts a lot as they were defiantly puffed up a bit after the last run.

I allready have a 3/16th shaft/teflon tube collet, but the strut that came with that setup does not have enough clearance to run the brass tube into the strut, which is something i would want because of the single drive cat setup. So id probably just need another strut with 3/16 bushing in it?

[sundog]

No, you don't need a gap with a 2-piece, but it needs to turn freely - which you can tell by loosening the motor coupling and turning it by hand. I personally like a 2-piece flex arrangement, but it does make it difficult to lube. And 4mm flex should be fine. It could be that the timing caused the overheating. Why do you suspect the vibration is in the strut? Could be the coupling or collet was a bit unbalanced and you have it 180 degrees out from previous setting (screw marks will still line up). After checking the flex for binding, run it with the flex disconnected to see if the vibration goes away.