Shaft Seals Care and Maint

[John_S]

I have seen it posted in a number of threads:

- Never run trolling motor out of the water. It will destroy shaft seals.

- Use STP Stop Leak (or other) to recondition the seals.


Until recently, never seen this info posted on iBoats or other places. At 1st, didn't give it much attention, but after numerous threads, and no question/discussion about it, began to wonder.


I have run all my trolling motors out of the water, at numerous times, checking things out. While I haven't run them for extended times (don't know why I would), never thought there was emminent danger of destroying the seals. Given there is no load on the prop, they spin right up, and there is no heat to speak of. I even went and downloaded the very latest user manual for one, and walked through all the recommendations, warnings, etc. Nothing about running out of water. Is this something that was a problem with very early designs, and not to worry with any modern ones? In other words, people should not be worried about running the motor out of the water for testing. Or have I just been extremely lucky?

I have never used any reconditioning on the seals, and again nothing in the manuals. Does anyone else use STP or other conditioner on seals? It sounds like an easy thing to do, but not even sure the seals are made of rubber. I thought they were more a oil based product. Is the Stop Leak fixing something else? In fact, the way I thought Stop Leak worked in a radiator system, wouldn't seem like it be the best for direct apply. ???

 

[fucawi]

Re: Shaft Seals Care and Maint

These posts have probably all come from me ..remember the rpm will be very high out of water compaired to in the water and if the seal is dry ...there it goes..you always lubricate lip seals when fitting but when do you lubricate the seal on your shaft ... Maybe the maker wants it to fail eventually.....I had an old oil seal internal dia 21mm ..soaked it for 3 weeks in the stop leak stuff ..19 mm . Its standard to put this stuff in engines with weeping seals causes a 4 % expansion ..I also put some in my lower unit...good for trim tilts too ...
Nothing to do with radiator seal .thats fine blocking particles/clumping agent for holes .this stuff soaks into the Neoprene of the seal
Now let the argument commence ......

 

[John_S]

Re: Shaft Seals Care and Maint

Well, I'd like to keep it to a discussion, not an argument.

I didn't think the seals relied on water for lubrication. I haven't seen any extreme rpms from running in the air. Be it speed coil or digital control. I have run them in the air at all speed settings. Have you seen or expeirenced damaged seals from running briefly in the air?

It has been a while, but thought a basic DC motor speed is goverend by the windings in it and voltage across it. A given DC motor with X voltage across it, will have Y rpms. With no load, there is little current draw. Put a load on it, and the motor has to maintain the same rpms. The amp draw will go up as the motor trys to maintain the rpms. If the motor can not reach rpms, the windings will start to overheat. Now, a heavy amp draw would tend to cause a slight voltage dip, and a lower speed. TM's use very low pitched props, such that the rpm can be reached. If you turn a trolling motor on high from a dead stop (not recommended) it is almost instantly up to speed. You don't hear rpms climb as the boat moves forward. Just reduced prop slip as boat comes up to max speed.


Sorry for the cross to radiator vs engine. I generally don't have allot of "faith" in additives. Back in the day, cork engine seals were famous for weeping. Didn't know there are issues with modern seals including neoprene.

 

[dingbat]

Re: Shaft Seals Care and Maint

The dry seal stuff is BS.

The seal faces are impregated with a variety of anti-friction substances as the natural lubricate. Carbon/ graphite or teflon is most common. In operation the graphite separates from the mixture and transfers to the hard face. This means that the seal face combination you are normally running is carbon on graphite and no additional lubrication is required.

Using a chemical to swell the seals to make them last longer is a stop gap measure that typically doesn't work very well, if at all.

 

[bassman284]

Re: Shaft Seals Care and Maint

emergencypopcornrun.jpg

 

[fucawi]

Re: Shaft Seals Care and Maint

As for rpm ..starter motor free running 11000 rpm cranking 2000 rpm ..some lube in the seal areas is a good idea .resisting corrosion and making sure it does not run dry ...If you dont like the gearbox seal expander use ATF or engine oil ...your motor your choice

Re props ...many people here use Model areoplane props instead of the standard plastic thing in about a 10 x8 size less amp draw for the same speed....you need 1 inch of pitch for every mph at 1000 rpm not allowing for slip ( 20 % or less )

 

[John_S]

Re: Shaft Seals Care and Maint

Out of the two items, the running in air destroying seals is of most concern. If you have any evidence or data on this, please post. When I get some time, I'll call MK and MG tech support and get their take on both. I'll report back what they say.

I do not agree with the rpm, but that is not the real question here. I did remove the prop on a couple of my trolling motors and looked at the back of the seals. Well tried to see them.

On the MG Wireless, there is a screw in plug. It looks like it is made of nylon. Not much of, if any gap at the shaft. The braid line that was wrapped around the shaft hadn't found its way in. From a schematic, it looks like there is a seal and bearing behind it. Decided not to remove plug to investigate further. There was not the hint of corrosion on any part.

I got a new to me MK this year, with a used boat purchase. It is a 36lb 4WD model, probably from the 90's. I have only run this in the air, so far. I removed the prop, and this one has a brass type plug, with no real access to the seal. Looks pressed in. Again, no corrosion.

I didn't look at my older one, a MG HVT. I'll take a look tonight.

A seal designed to keep water out, is not about to let oil in. At best applying any oil, will only touch the outside edge of the seal. Not sure if the oil would reach the seal edge on my wireless models.

 

[John_S]

Re: Shaft Seals Care and Maint

.you need 1 inch of pitch for every mph at 1000 rpm not allowing for slip ( 20 % or less )

How can I measure rpm?, especially in the water? I have been looking at ways to measure in the air with stuff I have around the house. My tractor uses a sensor that just counts the number of times a magnet on the flywheel passes by. Thought of taping a thin magnet to hub, and trying that. That won't work in the water, of course.

 

[fucawi]

Re: Shaft Seals Care and Maint

Will try some measurements..but many people here use electric boats ..you only need about 180W for about 4 mph some have test the motors with and without the oil seal and have discovered that a lot of power is absorbed by the seal ..10 Watts difference with seal in and out ..now not much but some of these boating nutters are fanatical about power loss ..so there is the potential to heat up the seal ..thing of a 15w soldering Iron ...thats hot ..the reves quoted were for a vehicle starter motor just as an example...

for rpm you could use one of those bicycle compouters ..that has magnet on wheel and pick up ..just need to calibrate it

 

[John_S]

Re: Shaft Seals Care and Maint

The bike computer sounds similiar to my flywheel measurement. But, what are they/you using in the water to get 1000 rpm readings for these prop modifications?, ie that is waterproof and not big enough to cause turbulance right in front of the prop? A picture of that set-up would be great.

On the electric boat, are we talking about a boat that is powered by a trolling motor(s) or some specialized boat? I think most/all trolling motors have been using perminently lubbed/sealed bearings for quite some time. So, not sure what oil seal that is eating 15W of electrical power???

My X voltage will yield Y rpm theory, is just that. I'm not sure and welcome explainations to why it is not. Starter motors are designed for very high current. Before gear reduction starter motor, you could burn them up turning the motor over for extended times. ie if you had enough battery reserve power to do so. On my diesel tractor there is a specific warning not to keep the starter motor engaged for over X minutes, or you will damage starter.

 

[fucawi]

Re: Shaft Seals Care and Maint

Have bought a bike computer so will let you know..also have lazer tacho to check accuracy ....

 

[kahuna123]

Re: Shaft Seals Care and Maint

complete bs on running the motor out of the water. So, think it though. If the seal was lubed by water it would have to leak. IN CLASS we learned to add a little grease besides what was already there. Once you water intrusion its all over. It was a long time ago but of course we ran the motors on a test bench out of water. I had to go to school to be able to get paid for warranty issues. ONCE in a great while we did a locked rotor amp measure. With motorguide, they were made so cheap at the time you would break them doing that. They had to be run in a tank with a amp meter. Besides the heat sinks for the speed controller were so cheap on the MG that they were mounted in the foot to have cooling.

 

[John_S]

Re: Shaft Seals Care and Maint

Was that Special Lube 101? That stuff is sticky and holds up well underwater.

One thing I did notice, I haven't put a dab of rtv on the prop pins of my newer motors, to keep them from easily sliding out and getting lost.

 

[fucawi]

Re: Shaft Seals Care and Maint

Bike tacho arrived today ..small magnet for the wheel and pick up for the fork...easily mounted to the Minn Kota 24v 85 lb Trolling motor ...gave 845 rpm free on 12v and 574 in the water butt ....only reads to 1000 rpm so could not read on 24 v and barrel too small to run on 24v ( too violent)

Magnet easy to mount inside the prop hub with the sensor on the end of the motor case inside the hub ..too cold to do much more ...

 

[TerryMSU]

Re: Shaft Seals Care and Maint

complete bs on running the motor out of the water. So, think it though. If the seal was lubed by water it would have to leak. IN CLASS we learned to add a little grease besides what was already there. Once you water intrusion its all over. It was a long time ago but of course we ran the motors on a test bench out of water. I had to go to school to be able to get paid for warranty issues. ONCE in a great while we did a locked rotor amp measure. With motorguide, they were made so cheap at the time you would break them doing that. They had to be run in a tank with a amp meter. Besides the heat sinks for the speed controller were so cheap on the MG that they were mounted in the foot to have cooling.

Kahuna:

I suspect that the intent of the water was for cooling of the seal and shaft, not for lubrication. I am not saying that one should or should not run out of the water, just that the water would provide a lot of cooling.

TerryMSU

 

[dingbat]

Re: Shaft Seals Care and Maint

Kahuna:

I suspect that the intent of the water was for cooling of the seal and shaft, not for lubrication. I am not saying that one should or should not run out of the water, just that the water would provide a lot of cooling.

TerryMSU

You don't need any type of cooling on a shaft running at 1000 RPM. Most radial shaft seals are designed for continuous operation between 200 and 400 degrees F. The flow of air induced by the shaft/prop would be more than enough to keep the seal and shaft temps well below those values.

Containments, bad bearings and ozone (dry rot) wipe more seals than everything else combined

 

[fucawi]

Re: Shaft Seals Care and Maint

so a spot of lube regularly on the seal will prevent " dry rot" are you saying

 

[TerryMSU]

Re: Shaft Seals Care and Maint

You don't need any type of cooling on a shaft running at 1000 RPM. Most radial shaft seals are designed for continuous operation between 200 and 400 degrees F. The flow of air induced by the shaft/prop would be more than enough to keep the seal and shaft temps well below those values.

Containments, bad bearings and ozone (dry rot) wipe more seals than everything else combined

Perhaps I mis-spoke. I still contend that the motor and thus the shaft will heat up, and that in water, they will be much cooler due to the contact with water. Hypothetically, it is possible that the shaft is dry and the motor is wet (or vice-versa), but not likely. Heat (whether from the seal friction or from the motor itself) will still damage the seal, and water will cool the motor and the shaft.

TerryMSU

 

[dingbat]

Re: Shaft Seals Care and Maint

so a spot of lube regularly on the seal will prevent " dry rot" are you saying

You would get better results with suntan lotion.

 

[kahuna123]

Re: Shaft Seals Care and Maint

No not really. The seal is not much different than a pinon style seal and it runs hot all day. I dont know on the new ones but on the old ones there were two seals back to back. We always added a little grease to the shaft when putting them back together. There is no heat running one out of the water unless something is wrong. I think it was a triode, but not sure that was mounted in the foot on the MG's. It did get hot but only under a load.