Bow Thruster Travel Adjustment


pstas2003 <no_reply@...>
 

We recently serviced our bow thruster and now the unit now longer comes up high enough to insert the pin easily.  There are (what appear to be) three adjustment pots.  Two are located above the control box and one below,  Of the two above, the one to starboard is labeled “B”  the one to port is unlabeled.  The one located below the control box is labeled “H”.

Are these indeed the adjustment pots and if so, which one is used to adjust the upward stopping point.

I have searched the manual and forum and can’t seem to located the information.

Thank in advance for any and all responses.

All the best,

Paul Stascavage
SM #466 - s/v Rita Kathryn
Cruising St. Lucia

www.RitaKathryn.com


thomas.kleman <no_reply@...>
 

Hey Paul- it seems like almost a two part problem......first, you want to get the pin in to create the seal. This can be done by just pulling the lift wire, lifting the thruster the remaining few millimeters to get the pin in. The second part involves the more complex task of adjusting the lift mechanism to achieve the correct height when the red indicator light indicates full lift on the unit.........personally, I have never mastered this. At one point I had it perfectly aligned but this yielded a new problem. With the holes perfectly aligned at full lift, there was no friction on the pin and in rough seas the pin actually slipped out after it was fully inserted. So I now lift it the last few millimeters by hand and insert the pin so the weight of the thruster holds the pin in place while keeping the seal firm. Bottom line, not a drop of water in the bow thruster bay. I will be anxiously reading these responses because one of the old salts always has a way to improve processes like these.

Tom Kleman
sm2k 422 L'ORIENT


---In amelyachtowners@..., <no_reply@...> wrote :

We recently serviced our bow thruster and now the unit now longer comes up high enough to insert the pin easily.  There are (what appear to be) three adjustment pots.  Two are located above the control box and one below,  Of the two above, the one to starboard is labeled “B”  the one to port is unlabeled.  The one located below the control box is labeled “H”.

Are these indeed the adjustment pots and if so, which one is used to adjust the upward stopping point.

I have searched the manual and forum and can’t seem to located the information.

Thank in advance for any and all responses.

All the best,

Paul Stascavage
SM #466 - s/v Rita Kathryn
Cruising St. Lucia

www.RitaKathryn.com


Craig Briggs
 

Hi Tom,
On the SN there is a fixed retaining post for the locking pin. You insert the locking pin fully through the shaft hole, then rotate it so the bent end goes behind the retaining post, preventing it from accidentally slipping out. 
When removed the locking pin stores down a hole on top of the port side the vertical support tube.
I suspect the SM is the same, but perhaps not.
Cheers, Craig SN#68 Sangaris


---In amelyachtowners@..., <no_reply@...> wrote :

Hey Paul- it seems like almost a two part problem......first, you want to get the pin in to create the seal. This can be done by just pulling the lift wire, lifting the thruster the remaining few millimeters to get the pin in. The second part involves the more complex task of adjusting the lift mechanism to achieve the correct height when the red indicator light indicates full lift on the unit.........personally, I have never mastered this. At one point I had it perfectly aligned but this yielded a new problem. With the holes perfectly aligned at full lift, there was no friction on the pin and in rough seas the pin actually slipped out after it was fully inserted. So I now lift it the last few millimeters by hand and insert the pin so the weight of the thruster holds the pin in place while keeping the seal firm. Bottom line, not a drop of water in the bow thruster bay. I will be anxiously reading these responses because one of the old salts always has a way to improve processes like these.

Tom Kleman
sm2k 422 L'ORIENT


pstas2003 <no_reply@...>
 

Tom,

Thank you for your response. 

I have been using the cable grab method to insert the pin, but what is the procedure to adjust the lift mechanism?

All the best,

Paul Stascavage
SM #466 - s/v Rita Kathryn
Cruising St. Lucia

www.RitaKathryn.com


greatketch@...
 

Paul,

On mine (which is older and might be a bit different...) the primary adjustment is where the cable attaches to the top of the motor.  If you loosen the jam nut, and pull the pin that hold the cable in place, there is a significant amount of vertical adjustment in the position of the motor by turning that fitting and varying the depth of thread in the motor.

I wouldn't adjust the position of the limit switches unless it was clear that was needed, and there was room in the travel of the jack screw to accommodate the change.

Bill Kinney
Sm160, Harmonie
Fort Lauderdale, FL


greatketch@...
 

Tom,

The correct adjustment is where you ended up.  The last few millimeters of lift certainly should be by hand, squeezing the wires together.  This makes sure the pin is actually taking the load of the motor (which is HEAVY).  It would be not good at all to have the jack screw supporting the weight of the motor when pounding into a head sea.  As you also noted, if the pin is not doing any actual lifting, it just falls out.

This adjustment also prevents the jack screw from "dead heading" against a excessive load.  This would also be very bad for it.

This is one case where the correct adjustment is much easier to actually achieve than the wrong one!

Bill Kinney
SM160, Harmonie
Fort Lauderdale, FL


Craig Briggs
 


Craig Briggs
 

Granted we're only talking millimeters, but it seems the lifting action should stop exactly at the level at which the pin can be inserted without squeezing the cables.. This will provide the proper compression of the shaft seals whether you pin it or not.
That is, if you need to squeeze the cables to get the pin in, either you're over-compressing the seals or they are under-compressed with the pin out.
We have ours lined up so the pin goes in snugly without squeezing the cables. Then, when we're making a passage and want to use the pin we insert it and then give a quick flip of the down switch to unload the cables so all the weight is on the pin..
As I mentioned in a previous post, we rotate the pin behind the locking post to prevent any possibility of it falling out, which is highly unlikely anyway what with all the weight on the pin. 

Craig Briggs, SN68

---In amelyachtowners@..., <greatketch@...> wrote :

Tom,

The correct adjustment is where you ended up.  The last few millimeters of lift certainly should be by hand, squeezing the wires together.  This makes sure the pin is actually taking the load of the motor (which is HEAVY).  It would be not good at all to have the jack screw supporting the weight of the motor when pounding into a head sea.  As you also noted, if the pin is not doing any actual lifting, it just falls out.

This adjustment also prevents the jack screw from "dead heading" against a excessive load.  This would also be very bad for it.

This is one case where the correct adjustment is much easier to actually achieve than the wrong one!

Bill Kinney
SM160, Harmonie
Fort Lauderdale, FL


Miles
 

Hello Craig,

Many years ago, Amel told me to never adjust the bow thruster the way you have done.  Making the lift motor raise it to the pin puts too much force on the motor.   It should stop where it requires a strong squeeze on the cable to get the pin in.  This is how the Amel people demonstrated it to me.  

Regards,

Miles

S/Y Ladybug, at dock 4 m Le Marin, Martinique


Craig Briggs
 


Craig Briggs
 

Hi Miles,
Interesting advice from Amel  I think it's a bit odd, frankly, and it seems not to have come with a "why" do this..

I rather think the logical adjustment, which I've done, is to have it simply and gently snug up against the "donut" gaskets AND have the pin hole in alignment. There is no strain or overload at all needed by the lifting motor.  

When, infrequently, we insert the pin for boisterous sailing, its taper on the end picks the motor up only about one more mm when inserted and it goes in snugly, keeping the weight of the motor off of the lifting mechanism. Then we "pop" the down switch for a second to totally unload the lift motor. And we rotate the pin behind the locking post.

I should think a "strong squeeze", as you (or "Amel") put it, will compress the donuts a whole lot.  Eric (or was it Bill?) said he squeezes up about 10mm, almost 1/2 inch - I don't think the donuts are even that thick, so when not pinned that logically means they wouldn't be making firm contact with the BT box at all.. As I said, "odd advice".

Do you "squeeze and pin" every time you use the BT?  Seems a pain especially for coastal day-hops. I'd posit that most of the time most of us are day hopping and not pinning the BT (and shouldn't have to), so why not have the donuts be in firm and proper contact with the BT box all the time so they can do their job for those inevitable times when it kicks up a bit and you haven't put the pin in?

Oh well - lot's of ways to skin a cat.

Cheers, Craig SN68


---In amelyachtowners@..., <milesbid@...> wrote :

Hello Craig,

Many years ago, Amel told me to never adjust the bow thruster the way you have done.  Making the lift motor raise it to the pin puts too much force on the motor.   It should stop where it requires a strong squeeze on the cable to get the pin in.  This is how the Amel people demonstrated it to me.  

Regards,

Miles

S/Y Ladybug, at dock 4 m Le Marin, Martinique


Craig Briggs
 

Hi Miles,
Interesting advice from "Amel", although lacking a "why" makes me wonder.

I've set my BT so when retracted the "donut" gaskets are gently compressed AND the hole in the lift is just a fraction below the pin. There is absolutely no strain on the lifting motor. Then, if-or-when I insert the pin it lifts the motor only about 1mm because of the taper on the end of the pin.  Maybe the Captain engineered it that way!, That relieves almost all force on the lifting mechanism. Then I "pop" the down switch to put absolutely all the load on the pin, not the cable/motor. I also rotate the pin behind the locking pin. No way to get loose.

If you need to put a "strong squeeze" on the cable you are lifting the motor a lot. Eric -or was it Bill? - said the squeeze lifts the motor 10 mm - about 1/2 inch - which, I think, is more than the thickness of the "donut" gaskets. Logically that says the donut gaskets are either not touching the BT housing without the pin or they are way too compressed after the squeeze - maybe that's why many owners are needing to replace them very frequently.

Do you "squeeze and pin" EVERY time you use your BT?  What a pain and I sure don't., Like most of us I think, most of my sailing is day hopping without the pin inserted. So why not have the "donut gaskets" do their job either with or without the pin in place.

Oh well, lots of ways to skin a cat.

Cheers, Craig SN#68

---In amelyachtowners@..., <milesbid@...> wrote :

Hello Craig,

Many years ago, Amel told me to never adjust the bow thruster the way you have done.  Making the lift motor raise it to the pin puts too much force on the motor.   It should stop where it requires a strong squeeze on the cable to get the pin in.  This is how the Amel people demonstrated it to me.  

Regards,

Miles

S/Y Ladybug, at dock 4 m Le Marin, Martinique