Runnning Motors at WOT on the bench

[mtbenjamin77]

This has been a disccusion at our local pond and we never found any common ground. For my setups I have run the motor on the bench for only a split second to check for high frequency vibrations, correct rotation, endpoint verification, but never run at WOT for longer than literally a fraction of a second. I don't even like to punch the throttle with the boat in the water. I just believe that induces unecessary strain on every component involved. When I launch my boat I start slow and gradually get up to speed. Once on a plane I will accelerate hard out of a turn into the straight, but a lot of the guys at our pond just toss the boat in and nail the throttle. Anyone chime in here, what ill effects come from WOT w/ no load.

[lenny]

Well let see now,
No warming of the cells and no water flow to any thing and a full load dead start,
Sounds like they do not care about there boats,
When you get in any vehicle you should warm it up some and check things over,
Just like anything thing that is mechanical and could have a failure.
Just like people need to get stared moving slowly in the morning or from setting to long,
If I just jump on my girl with out warming her up that is not a smart move.

Also full rpm with no load is not the smarties thing to do with anything that is mechanical.

But that just me.

[Megabiker98]

If I just jump on my girl with out warming her up that is not a smart move.

Hahahahahaha perfect example! Lol couldn't agree with that statement more though, everything should be "warmed up" before anything!

[tlandauer]

@ mtbenjamin77, I feel exactly as you do and I also think that even with the correct clearance, sometimes the stub shaft has a bit of free play in the bushing ( especially brass) and at WOT, there is unnecessary fast vibration that will only be dampened by water, you can b/p/s a prop all you want, there is no perfect balance and since the motor , collet and flex cable are just assumed balanced, these things are not made for the NASA Space Shuttle.
@ Lenny, you could not have said it better. My 1990 Buick Le Sabre lasted 350,000 miles with NO repair done to the engine and trans. I did not pamper the car, just used common mechanical sense. Infact, every car I owned all lasted over 200,000 without major repairs.
As for the lady, well, we all know how goes the "drill...''

[Fluid]

Another question - what good does it do? Answer - none. It does not at all replicate WOT performance on the water. Too, BL motors running without load heat up FAST because the energy is converted to heat, not spinning a prop. The OP's friends can do what they want, it's their boat, but IMO one should NEVER run a water-propped boat WOT out of the water. Airboats are different for obvious reasons.



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[martin]

Apart from just checking everything is working & running in the right direction running with no load at wot is a waiste of time & will possibly just cause unnesessary damage. I have friends that when they connect up their boats to run always want to give a full throttle blast just to here the thing run. One even done this on the bench at home & had a wrag that was on the bench wrap around the prop & destroy the flex & bend the stub & also rip the stuffing tube out of the hull.

[Cooper]

Agreed, just not good mechanical practice to add undo stress to any components. Personally i don't think it is hurting much (if everything is in working order) but still just not sound practice to do for more than a second. When running without load and out of water the vibrations can and will magnify to the point of stressing the weak point to wear more or even for extended time to break. I agree there is no one running a balanced system so these minor vibrations and heat build up are just inviting the gremlins to work. But again a second or two shouldn't really hurt, just not what I do. Now I do "tap" the throttle after working on boat to make sure everything running correctly but only for a split second.
Guess its just preference on care of equipment, I'm organized and clean with my work area and that transfers to my equipment while I've seen some so cluttered and unorganized that I wouldn't know where to start but when we hit the water we are still at an equal, so just depends. I break stuff and so do they.

[oscarel]

When you get in any vehicle you should warm it up some and check thing over,
Just like anything thing that is mechanical and could have a failure.

Try telling my wife this! We have a 4runner with over 250K and it's never had anything major done to it. She didn't let it warm up any before driving.

[LuckyDuc]

I start up my vehicles and go too. Letting them idle for 15 minutes just wastes fuel. They warm up much faster under load/driving. The important thing is to keep the rpms low until the motor reaches operating temps.

While running a boat motor at WOT out of the water is not a good idea, it happens each time the boat jumps a wake and catches air momentarily. The motor hits full RPM and then is immediately loaded up when the prop makes contact with the water again.

[mtbenjamin77]

Thanks for all the input. I have yet to find any kind of direct ill effect of running at WOT w/o a load with an electric motor. Now if we're talking about an IC engine that's a different story. No load on a nitro motor will throw a rod in a heart beat. The only ill effect I can really think of in an electrics motor would be the bearings turning too many rpms or a risk of separating the magnents on the rotor if you spin more rpms than it's rated for. But then again If you're spinning higher rpms than the motor is rated for then you got the wrong setup all together. Good thing is bearings in an FE motor are simple and fairly cheap. Thanks again for all the input and keep it coming.

[viper1]

Not relevant to the OP, but I have high KV small BL motors for planes that would desintegrate in 2 seconds or less if I would run 'm without prop at WOT.
sorry

[Darin Jordan]

I never run motor IN the boat at anything other than a quick blip to make sure the prop is spinning the correct direction.

I have a bench testing setup, however, where I mount the motor and do bench testing where I've held WOT for many seconds in order to get a steady data reading on my EagleTree or Castle ICE. I've done this boat loaded (airplane prop) and unloaded (nothing attached). It's not common practice, and I wouldn't recommend it if you have to buy the motor you are testing. In my case, I know where the tree grows, and the testing was done in the name of "science"...

It's not generally a good idea to WOT the motors on the bench, especially if they are in the boat, connected to the driveline. Tears up shafts, bearings, etc...

[mtbenjamin77]

Darin,

Thanks for the input. I was hoping you'd offer some input. Thanks my friend

[lohring]

I ran this 2030 Kv UL-1 motor at WOT with the load off more as a dyno test than anything else. No problems with either. By the way, with no load there's very little power loss so heating isn't an issue.

Lohring Miller

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[madmikepags]

If your motor is close to its max rpm when loaded then it will be over that when unloaded, that's when rotors laminations can come unglued and start to fall apart, especially cheaper made motors. I've had this happen with cheap motors and had it happen with a high end German motor, one blip to wot and "bang". Run it in the water where it's supposed to be run.