Re: [PSUBS-MAILIST] re-wiring trolling motors?

[MerlinSub@t-online.de (Carsten Standfuß)]

My 5 cents: 

The holder-shaft on the MK is made from carbon - carbon has a high 
electric potential against for example aluminium (I have not the figure 
- but it is high). I remove the shaft and use the hole with the thread 
for an o-ring sealed drain plug.
This hole is now at the deepest point of the engine and can be easy open 
from outside. 
Its on my pre-dive checklist to open this plug and look for leakwater
or moistures. The MK 55 Ex I purchase has 4 small wires which goes
inside the 
carbon shaft to the engine, 2 of them are + and 2 are -. Both +- wires
ends
on the same conector inside  the engine and inside the controller. 
So I replace the 4 wires by only 2 bigger wires for the reason I wish
not to 
drill four watertight cable connectors to the motor-hull and 4 others 
to the pressure hull. To connect this 2 cables inside the motor was much 
more difficult than the 4 small ones because of the space the bigger
diameter
needs, but it is possible if you use the small space between the
magnets. 

I used my engine with air-compansating on a central scuba regulator 
and a 0,7 Liter pressure bottle together conected
with the 4 thrusters and the 3 batteries (all outside). Works well. 
After a 3 hours dive last year the air compensator pressure system lost
all the
pressure air for the reason of a bad conection (the high pressure 
bottle connector was selfmade from stainless steel and the tread was
just 
a very little to short.)
All engines end batteries were flooded with freshwater 
from the lake. All engines runs - but clear much slower. 
The plug on the bottom of the engines helps much to drain the system
after this event. 
I have allways a small amount of motor-oil inside the engines to prevent
corrosion. 

If I remenber right the three motor-hull parts of the MK are connected
with o-rings. 
I used the Sgt.Peppers sub only in lakes and for that reason there are
no anodes 
on the engines. If I will use the sub in saltwater I will also maybe not
use anodes 
because of the relative short times the sub is in the water. The next
sub project 
Cssx will be used only in saltwater and will be in the water the hole
year. 
For this reason all steel parts in the water and special the sternpart
with the 
steel rudders and the (bronze-) propellers and will be protectet. 

Carsten

Herve Jaubert schrieb:
> 
> Pat,
> If you decided not to put a sacrificial anode somewhere on the end part of
> the motor, the one where is the little fin, and if there is no electrical
> continuity bewtween the axle and the steel shaft, then you would have to put
> a connecting wire between the parts of the case , this technic is commonly
> used by boat manufacturers they run a copper wire throughout the hull to
> make sure everything is connected. The motor case comes  in 3 parts( MK or
> MG) and is covered with a coating that probably does nt make good continuity
> when they are assembled ( 1 on 3 are correctly connected), to ensure
> continuity you have to attach a copper wire between the end part of the
> motor and the shaft or directly on the anode. This wire could be outside the
> body (uggly) or inside. you have then to open the body and attach the wire
> inside the end of the motor case on a non moving metallic part. There is
> another possibility : there is a small thread outside the case on the end
> part of the motor, if you could find a sacrificial anode that could be
> screwed in there you have your galvanic corrosion protection, unfortunately
> the available space between the motor and the prop is very small, so the
> anode should have the size of 1/4" screw and be replaced more often.
> I was not successfull in finding such small anode, but it is the best way
> since there is nothing more to do than screwing that little piece.
> Even if you don t use the shaft or if the shaft is not in contact with salt
> water, there is still galvanic corrosion of the engine with the motor axle
> and some screws being in the water.
> So if you keep your sub for long period of time in the ocean you should make
> sure that the anode is electrically connected to the axle.
> Before you make any work check your engine when you purchase it , may you
> get lucky and there is good connection.
> I don t know if the people of MK or MG are aware of this problem but they
> are selling motors for saltwater that fail corrosion control.
> It is true that part of the controller in the MG is in the lower unit. But
> in my subs I don t mind, because I don t use it!
> I don t beleive electronic variable speed is usefull for a sub, important
> momentum , too heavy and too slow , I choosed to power my subs with 2
> speeds, slow / fast, and in between I use bursts of thrust to achieve
> variable speeds taking advantage of the momentum.
> The advantages is you don t need the upper unit, slow speed is in 24 Volts,
> fast speed is in 36 Volts.
> you use only 2 of the wires and forget the controller and its wires inside
> the lower unit.
> Other adavantage is the cost, less expensive since you don t need the upper
> unit, if you were interested I sale lower units MG 107 alone , forward and
> reverse, 36 / 24 Volts, plus the stainless steel shaft, plus the sacrificial
> anode to be mounted on the shaft and the prop kit for only $280, not
> including shipping via UPS or check with your motor dealer, but this
> solution is the most cost efficient.
> I ll have to check tomorrow at the factory the exact dimensions of the lower
> unit.
> regards
> Herve Jaubert
> 
> ----- Original Message -----
> From: Captain Nemo <vulcania@interpac.net>
> To: <personal_submersibles@psubs.org>
> Sent: Saturday, November 25, 2000 6:59 PM
> Subject: Re: [PSUBS-MAILIST] re-wiring trolling motors?
> 
> >
> > ----- Original Message -----
> > From: "Herve Jaubert" <caribsub@coqui.net>
> > To: <personal_submersibles@psubs.org>
> > Sent: Saturday, November 25, 2000 7:54 PM
> > Subject: Re: [PSUBS-MAILIST] re-wiring trolling motors?
> >
> >
> > > It is actually simpler than to rewire the motor. (disassembling
> required)
> > > This procedure is important, otherwise under frequent use your motor
> will
> > be
> > > galvanic corroded.
> >
> > Herve,
> >
> > What kind of rewiring are we talking about here.  Please describe.
> >
> > VBR,
> >
> > Pat
> >
> >
> >