Bowthruster Service - HELP requested - sheared bolt


David Vogel
 

Hi all,

On the hard, and servicing the bow-thruster.

One of the four bolts that secure the carbon-fiber torque down-tube to the motor assembly has been particularly difficult to remove. Heat, penetrating oil, patience - no joy. Wait a few weeks until good humor returns. Return for more of the same - no improvement. Wait some more. Eventually, the hex hole rounded out. Now, finally, returning today with some more penetrating oil and heat, and then use of maximum own force via a 8" spanner and a so-called 'easy-out'.

Result: movement, but of the wrong kind -- the head of the hex-bolt has sheared off at the point the bolt thread enters the metal base of the electric motor. (I didn't know that I could muster enough strength to do that.)

Unfortunately, the broken bolt is that one on the starboard side, facing 45º forward, and thusly very difficult to get access to; no direct 'straight-on' access or line-of-direct-sight is possible. The three other bolts have been easy to remove, although with rounding of the hex, and some thread damage, indicative of earlier travails - so all are due for replacement.

With the remaining (broken) bolt still securing the torque-tube to the base of the electric motor, it seems impossible to be able to rotate the electric motor assembly, to enable to drill out the bolt. So, how to disengage the torque-tube from the electric motor, to enable to drop the bow-thruster out of the hull for service?

Does anyone any experience in solving this problem? Or, any ideas at all on how best to proceed?

Thanks, in advance.

David
SM#396, Perigee
On-the-hard, Marsden Cove Marina


 

David,

This happened to a client of mine when I was with him for training in Malta. We used a 90° Angle Drill Attachment and drilled the bolt out. We got lucky and did not damage the threads. I hope you are lucky.

Once you drill the remaining bolt to a point just inside the cast iron motor base (green circle below), the bow thruster tube will fall from the motor. This allows you to seek the aid of a machine shop to use a drill press to drill the remaining bolt out without damage to the threads which are tapped into a bronze inner tube inside the GRP shaft.
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CW Bill Rouse Amel Owners Yacht School
720 Winnie, Galveston Island, Texas 77550 
   

On Tue, Oct 18, 2022 at 12:34 AM David Vogel <david.vogel@...> wrote:
Hi all,

On the hard, and servicing the bow-thruster.

One of the four bolts that secure the carbon-fiber torque down-tube to the motor assembly has been particularly difficult to remove.  Heat, penetrating oil, patience - no joy.  Wait a few weeks until good humor returns.  Return for more of the same - no improvement.  Wait some more.  Eventually, the hex hole rounded out.  Now, finally, returning today with some more penetrating oil and heat, and then use of maximum own force via a 8" spanner and a so-called 'easy-out'.

Result: movement, but of the wrong kind -- the head of the hex-bolt has sheared off at the point the bolt thread enters the metal base of the electric motor.  (I didn't know that I could muster enough strength to do that.)

Unfortunately, the broken bolt is that one on the starboard side, facing 45º forward, and thusly very difficult to get access to; no direct 'straight-on' access or line-of-direct-sight is possible.  The three other bolts have been easy to remove, although with rounding of the hex, and some thread damage, indicative of earlier travails - so all are due for replacement.

With the remaining (broken) bolt still securing the torque-tube to the base of the electric motor, it seems impossible to be able to rotate the electric motor assembly, to enable to drill out the bolt.  So, how to disengage the torque-tube from the electric motor, to enable to drop the bow-thruster out of the hull for service?

Does anyone any experience in solving this problem?  Or, any ideas at all on how best to proceed?

Thanks, in advance.

David
SM#396, Perigee
On-the-hard, Marsden Cove Marina






Bill Kinney
 

David,

Do a google search for “flex drive angle drill chuck” and you’ll find the same idea as Bill R suggests in a more flexible format.  It MIGHT make reaching a bit easier.

You might need a shorter drill bit than standard to reach.  Don’t be afraid to shorten one if needed.  Also, once you get a drill in there, this is a bit easier than you might think because the steel base of the motor is quite hard, and this makes it easier to drill straight down the screw.  

Patience will will this battle.

Good luck!

Bill Kinney
SM160, Harmonie
Port Louis, Grenada
http://www.cruisingconsulting.com


David Vogel
 

Hi Bill x2,

Thanks for the assistance – this is still a works in progress.

As you say BillK, patience, a great deal of it, and perseverance, is being called for with this particular job.

Best,

David





From: <main@AmelYachtOwners.groups.io> on behalf of Bill Kinney <cruisingconsulting@...>
Reply to: <main@AmelYachtOwners.groups.io>
Date: Wednesday, 19 October 2022 at 5:43 am
To: <main@AmelYachtOwners.groups.io>
Subject: Re: [AmelYachtOwners] Bowthruster Service - HELP requested - sheared bolt

David,

Do a google search for “flex drive angle drill chuck” and you’ll find the same idea as Bill R suggests in a more flexible format.  It MIGHT make reaching a bit easier.

You might need a shorter drill bit than standard to reach.  Don’t be afraid to shorten one if needed.  Also, once you get a drill in there, this is a bit easier than you might think because the steel base of the motor is quite hard, and this makes it easier to drill straight down the screw.  
Patience will will this battle.
Good luck!

Bill Kinney
SM160, Harmonie
Port Louis, Grenada
http://www.cruisingconsulting.com


From: <main@AmelYachtOwners.groups.io> on behalf of Bill Kinney <cruisingconsulting@...>
Reply to: <main@AmelYachtOwners.groups.io>
Date: Wednesday, 19 October 2022 at 5:43 am
To: <main@AmelYachtOwners.groups.io>
Subject: Re: [AmelYachtOwners] Bowthruster Service - HELP requested - sheared bolt

David,

Do a google search for “flex drive angle drill chuck” and you’ll find the same idea as Bill R suggests in a more flexible format.  It MIGHT make reaching a bit easier.

You might need a shorter drill bit than standard to reach.  Don’t be afraid to shorten one if needed.  Also, once you get a drill in there, this is a bit easier than you might think because the steel base of the motor is quite hard, and this makes it easier to drill straight down the screw.  
Patience will will this battle.
Good luck!

Bill Kinney
SM160, Harmonie
Port Louis, Grenada
http://www.cruisingconsulting.com