Wednesday, July 18, 2012


One of the hardest areas to work around when BIANKA had the Westerbeke diesel was the stuffing box. Because the boat had a V Drive transmission the prop shaft ran under the engine and transmission:

Trying to get two wrenches to adjust the stuffing box was not in the category of what I would call fun. There was hardly enough room to move the tools because of the tight space:

Just looking at these old pictures of the limited space and the grime gives me the shakes.  That all changed once I put in the Thoosa 9000 electric propulsion system. Now access to the stuffing box for adjustment is no longer problematic as it was with the diesel:

The area is easy to get to and open and which means there is a lot of range to use the wrenches for adjustment. Best of all it is clean!  Capt. Mike is very happy about that. As I mentioned I've gone five years without a lot of maintenance on the system including the stuffing box once the initial adjustments were done.
I think part of the reason is because there is so little vibration when using an electric motor for auxilary propulsion there is little need to adjust or replace the packing around the shaft when compared to the vibration of operating a diesel engine. But, since this is a standard stuffing box and not one of the newer Dripless Shaft Seal type stuffing boxes that does not mean they won't drip a little bit. Indeed that is what they are supposed to do to make sure the packing is lubricated and not compacted to tightly around the shaft. 

 When I purchased my electric propulsion system five years ago. I had the distributor at the time provide me with a shaft coupler to connect the motor with the prop shaft. Unfortunately, the one he provided was made of steel but, not stainless steel. Since I was new to the idea of electric propulsion I trusted his choice. Here are the couplings side by side:

 Well, five years of drips from the stuffing box had started to rust one end of the original steel shaft coupling. Now there's a saying that "rust is natures Loctite" and it may perform that function for awhile but, it won't do that forever. Which brings me to why I'm doing this maintenance sooner rather than later.

 The fact is a stainless steel coupling would have been a better choice to connect the stainless steel shafts of the motor and prop. I decided that removing the motor would allow better access to the coupling and since removing the electric motor is easy and weighs only about 45 lbs it was a no-brainer. I just removed the four screws and two bolts shown in the previous post and lifted the motor away from the bracket :

Access to work on  the rusted coupling was now even better:

I was hoping that I would be able to remove the eight bolts holding the two piece shaft coupling to the shafts easily just using a ratchet with the proper allen head bit:

But, unfortunately despite spraying the bolts with PB Blaster  over several weeks I was only able to remove four of the bolts with the ratchet.  I guess it's true that "rust is natures Locktite" after all. Oh well time to take out the Dremel Tool  and cut through the rusted bolts in the coupling with a  Dremel reinforced cut-off wheel.

 and remove the old coupling:

Here is an inside view of the removed rusted coupling:   

and a look at the stainless steel replacement:

Once to old shaft coupling was off I cleaned the shafts with some denatured alcohol and heavy duty paper towel and clamped on the new coupling and torqued it down:

CAPT. MIKE NOTE: Before I put the screws in the coupling I coated the threads with Ultra Tef-Gel  which will help prevent any future corrosion issues and make it easy to remove the coupling in the future without having to use a Dremel tool to cut the through the screws. 

Once that was done it was a simple process of putting the motor back onto the frame. I tightened the two bolts and four screws and the motor was mounted ready to be hooked up to the controller:

Well, that was an easy repair and I did not have to contort and squeeze my six foot two inch frame into positions and spaces it was not meant to be in. I did the entire motor removal and coupling replacement while remaining inside the main cabin of BIANKA.  There was no need to empty the cockpit lockers and squeeze through a hatch like when I had the diesel on board. It's just another reason why I love my Thoosa 9000 electric propulsion system.
Since I had already removed the motor . It seemed like a time to check out the motor after five years of use. I'll show that in a future post.


SMR said...

Excellent post on changing out your coupling! From the pictures I can see there is some surface rust on the black motor frame. Just like any motor/engine in a marine environment there will be rust. This is not a sign of a problem with the motor, only that it is time to do some touchup with the anti-rust paint. The Thoosa & Triton dealer in Hawaii told us about a corrosion block product they swear by in the islands. We have not had a chance to try it out, but H&C Marine in Maui says that it is widely used on all boat systems over there. Here is a link to the product:
Looking forward to your next post Capt. Mike!
Sally Reuther, CEO
Clean eMarine Americas

Gregory Martin said...

Interesting post! Rust sucks and so I use stainless for as much as possible. I couldn't find a stainless coupling, so I used a regular steel one, painted with several coats of galvanizing/ zinc paint and with stainless bolts. I notice in your pictures, the shaft diameter of the motor and prop shaft is different. What are the sizes? Against the advice of the people in Denmark, I kept the same shaft as with my diesel- 22 mm, instead of the recommended 25 mm, figuring that the electric motor would vibrate less, be turned less and be subject to less stress than the diesel put on the shaft. Not to mention, replacing the shaft would have been a huge pain, as it would require a new cutless bearing, PSS seal, re-machine the prop... over 1500 NM logged now with the system (most under sail of course) and no problems yet! :) -Greg

Capt. Mike said...


The shaft on my boat is 1 inch (25.4 mm) not sure what the shaft size is coming off the motor but, it I suspect the standard ASMO Marine shaft size. I got the new coupling from Clean eMarine Americas the distributors for Thoosa systems in the US and just told them my prop shaft diameter.

driftwood said...

Thanks for the detailed post as always. I appreciate that you also link to the tools and materials you use so the rest of us can learn from your efforts as well.

Capt. Mike said...


Thanks for the nice comments. I'm glad the posts help inform others as well as serve as a log for me on the repairs and projects I'm doing on board.

Anonymous said...

thanks for sharing.