Bowthruster - hex-nut securing he motor to down-tube is stripped out


David Vogel
 

Greetings fellow Amelians,

Requesting help with a 'small' problem. After an extended service interval (>3-years since last service of the Bowthuster by AMEL MQ, the unwanted delay due to cruising French Polynesia in COVID times, closed borders, and so on), we're now securely in NZ, primarily for the purposes of attending to long-overdue rounds of routine maintenance - including as a high priority the Bowthruster and C-Drive.

Three of the four 6mm hex-bolts that secure the bowthruster motor to the fiberglass (?) torque-tube have been removed without undue problems - desite some rust clearly evident (due I think to the aging neoprene compression seals) with just the regular tightness as expected, but overcome with normal force of a 15cm shifter (no heat or penetrating oil needed).

Unfortunately, the fourth bolt - the starboard-hand one oriented forward - was found to be almost completely stripped, and the limited attempt to shift it finished the job. It now presents a round hole, which provides no ability to use an Allen key (either 6mm, or the next size up in imperial) to gain the necessary purchase. The forward-facing location presents challenges in terms of access needed to drill and tap in an "Easy Out". Without drilling, the easy-out can not be inserted far enough to gain any useful purchase. I have applied heat (MAP//Pro torch) as close as possible to the nut head. I am also soaking the joint (and the whole motor-tube interface area) with PB Blaster (now also anticipating problems with dropping the tube away from the motor assembly).

Has anyone faced this problem with a rounded hex-bolt before, and found a solution?

Or are there any other tips and trick, hints or suggestions?

Thanking you in anticipation, and with kind regards,

David
SM#396, Perigee
On-the-hard, Riverside Drive Marina
Whangarei, New Zealand


Colin - ex SV Island Pearl
 

Hi David

Nice to see you guys are slowly progressing closer to home. Congrats on your trip so far since we last shared drinks together on Island Pearl in Panama. We look forward to seeing you guys back in Brisbane someday.

I do not have a solution for your problem, so best wait for the smarter engineer folks to wake up in Europe & the USA with good answers to this, which I am sure will not be too hard.

The reason for this note is a suggestion ..... Go down to a local bicycle shop near you and purchase a new rubber inner tube for a large and as broad as a possible bicycle wheel. Take this, cut it across to make a long tube, then cut a slit all the way up through it to form a new long, broad single layer of rubber. Always keep this on board to wrap tightly around the base of your thruster if ever you see any leaks there in the future. It works perfectly and even with a badly damaged seal if that occurs at anytime whilst out cruising. In such an emergency it will keep every drop of water out! 

We did this in the Indian Ocean after replacing our bow thruster in the Maldives. At the time we did this in-water, and Amel sent a complete new bow thruster out from France but did not send us a new top rubber ring (the one inside the boat) and hence, although we never ever got water in there at any other time ever, between Chagos and Rodrigues we had huge 6m seas and winds and extreme conditions and en route found about 1 liter per day of seawater getting into the front bilge on that trip. All I could come up with in Rodrigues was this primitive bicycle-type solution, but it worked a treat, and we never had another single drop of seawater till reaching Durban where we were able to lift the boat for all her two-year maintenance, including replacing that all-important top seal. In fact, this system worked so well that it became my standard practice for us to wrap it around that base area of our bow thruster just after leaving the harbor on each and every ocean crossing thereafter "just in case"!  Of course, for all local, Caribbean, and Pacific Country cruising we never put it on, but for long crossings, it was a wonderful comfort to have handy.

Best regards to you both
Colin 
ex Island Pearl II
Brisbane

On Tue, Dec 7, 2021 at 11:10 AM David Vogel <david.vogel@...> wrote:
Greetings fellow Amelians,

Requesting help with a 'small' problem.  After an extended service interval (>3-years since last service of the Bowthuster by AMEL MQ, the unwanted delay due to cruising French Polynesia in COVID times, closed borders, and so on), we're now securely in NZ, primarily for the purposes of attending to long-overdue rounds of routine maintenance - including as a high priority the Bowthruster and C-Drive.

Three of the four 6mm hex-bolts that secure the bowthruster motor to the fiberglass (?) torque-tube have been removed without undue problems - desite some rust clearly evident (due I think to the aging neoprene compression seals) with just the regular tightness as expected, but overcome with normal force of a 15cm shifter (no heat or penetrating oil needed).

Unfortunately, the fourth bolt - the starboard-hand one oriented forward - was found to be almost completely stripped, and the limited attempt to shift it finished the job.   It now presents a round hole, which provides no ability to use an Allen key (either 6mm, or the next size up in imperial) to gain the necessary purchase.  The forward-facing location presents  challenges in terms of access needed to drill and tap in an "Easy Out".  Without drilling, the easy-out can not be inserted far enough to gain any useful purchase.  I have applied heat (MAP//Pro torch) as close as possible to the nut head.  I am also soaking the joint (and the whole motor-tube interface area) with PB Blaster (now also anticipating problems with dropping the tube away from the motor assembly).

Has anyone faced this problem with a rounded hex-bolt before, and found a solution?

Or are there any other tips and trick, hints or suggestions?

Thanking you in anticipation, and with kind regards,

David
SM#396, Perigee
On-the-hard, Riverside Drive Marina
Whangarei, New Zealand







--
Colin Streeter
0411 016 445


Dominique Sery
 

Hello David,

I had a similar problem. I used a Torx bit (slightly larger size) inserted with force with a hammer.
I then used a ratchet wrench and the recalcitrant screw came.
I don't know if this would work for you but it did for me.

Sincerely
Dominique
A54#16 Irko
Ashore, Kilada, Greece


Chris Doucette
 

Hi David,

I have done a lot of work on the bow thruster these last few months..  In Fact I have rebuilt the entire thing inclusive of the motor bearings.  Basically, count on drilling out that bolt and re- tapping the hole..  It really does not matter if it ends up 9mm vs the original 8mm. But first- get it drilled out. You might have to find a short 8mm drill bit with a right angle drill adapter. Those steel screws go into a brass fitting inside the bow thruster shaft.  It  is what you will tap eventually. Replace the bolts with quality 316 SS bolts, with copious anti-seize. 

Once you get it all out- be sure that the bearing in the base of the motor is going to be shot! I took everything appart in the motor also to change the bearings and snap washers, cleaned, brushed off rust, chemically treated the rust, and sealed that large steel base with epoxy and paint.  It looks like new and will not rust as it did. Re-tapped all the screw holes in the brass part. Almost all done here - bow thruster painting is underway and then assembling. 

Chris

Amarok, SM 385 



On Mon, Dec 6, 2021 at 8:10 PM David Vogel <david.vogel@...> wrote:
Greetings fellow Amelians,

Requesting help with a 'small' problem.  After an extended service interval (>3-years since last service of the Bowthuster by AMEL MQ, the unwanted delay due to cruising French Polynesia in COVID times, closed borders, and so on), we're now securely in NZ, primarily for the purposes of attending to long-overdue rounds of routine maintenance - including as a high priority the Bowthruster and C-Drive.

Three of the four 6mm hex-bolts that secure the bowthruster motor to the fiberglass (?) torque-tube have been removed without undue problems - desite some rust clearly evident (due I think to the aging neoprene compression seals) with just the regular tightness as expected, but overcome with normal force of a 15cm shifter (no heat or penetrating oil needed).

Unfortunately, the fourth bolt - the starboard-hand one oriented forward - was found to be almost completely stripped, and the limited attempt to shift it finished the job.   It now presents a round hole, which provides no ability to use an Allen key (either 6mm, or the next size up in imperial) to gain the necessary purchase.  The forward-facing location presents  challenges in terms of access needed to drill and tap in an "Easy Out".  Without drilling, the easy-out can not be inserted far enough to gain any useful purchase.  I have applied heat (MAP//Pro torch) as close as possible to the nut head.  I am also soaking the joint (and the whole motor-tube interface area) with PB Blaster (now also anticipating problems with dropping the tube away from the motor assembly).

Has anyone faced this problem with a rounded hex-bolt before, and found a solution?

Or are there any other tips and trick, hints or suggestions?

Thanking you in anticipation, and with kind regards,

David
SM#396, Perigee
On-the-hard, Riverside Drive Marina
Whangarei, New Zealand






Bill Kinney
 

David,

I feel your pain! I never ran into that particular problem in that place, but I have an idea or two for you.

Rather than using the long version of the "EZ Out" try the shorter ones, usually called "multi-spline extractors"  They are short enough they will frequently grab in a stripped hex hole without drilling, and short enough you can put a good deal of torque on them without them tipping over.

The look like this: 


The down-tube is fiberglass, so be careful with heat!  Since the bolt is not threaded in to the motor casting, applying heat there is not likely to help.

Last idea, I am not sure the exact alignment, but you can get some REALLY long drill bits.  Electricians use them when running wires.  They might make it possible to drill out the bolt in it's current location if you do not have to fit the drill head in there.

Bill Kinney
SM160, Harmonie
Brunswick GA, USA (For the next few hours...)