Sternthruster problems - advice?

[MapisM]

if the seal for the big deck hatch is leaking underway (which is 99% for sure the problem)

Why are you assuming that, J?
My swim platform stays bone dry underway, at least in decent sea conditions, and I'd expect the F630 to behave similarly.
I guess it might not be the case with your boat, but there's a big difference in this respect between platforms built above the hull vs. overhanging.

That aside, I wouldn't be surprised if the rudder stock bearings wouldn't leak one single drop when static, but let some water in while cruising, particularly at speed. Torsional forces on rudder shafts of a P boat are pretty substantial, underway!

 

[MapisM]

To mount the motor higher you have to cut a new 150mm hole in the boat.
And fill the old one in.....

I think PF was suggesting to move just the motor, not the tunnel/prop.
Not that I'd remotely consider going that way, mind. Getting rid of the whole s/t would be much simpler and more effective!

 

[Elessar]

I think PF was suggesting to move just the motor, not the tunnel/prop.
Not that I'd remotely consider going that way, mind. Getting rid of the whole s/t would be much simpler and more effective!

The motor sticks through the hull on the front of the tunnel to which it is bolted. To move the motor you have to move the tunnel.
And the hole.

 

[baylabayla3288]

Regarding upgrading the thruster prop with one with more blades I did this on my current boat. I think I feel more thrust in addition to more silent operation. Vetus actually increased also the spec for the max thrust despite using the same motor when they vent for the new propellers. Worth trying as these does not cost so much.

I also have some water ingress in the “spoiler” (Ferretti language) compartment despite new hatch seals. Sometimes in heavy seas with a lot of spray from the beam I can see both the engine and spoiler compartment bilge pumps running from time to time. I suspect that there is an opening between the engine room and the spoiler compartment, maybe higher up in the hull, where the water could find its way from the side vents all the way back.

 

[Elessar]

I think PF was suggesting to move just the motor, not the tunnel/prop.
Not that I'd remotely consider going that way, mind. Getting rid of the whole s/t would be much simpler and more effective!

I agree BTW that S/Ts are not essential on most planing, twin engined mobos.
Not true of displacement boats with a little keel and definitely not true of single engined, planing shaft drive boats which are almost impossible without them.
But if I bought a boat with one a) it would have to work and b) I wouldn’t take it off. They can be handy.

 

[MapisM]

The motor sticks through the hull on the front of the tunnel to which it is bolted.
To move the motor you have to move the tunnel.
And the hole.

That has nothing to see with what PF suggested (as I understoood), i.e. unbolt the motor alone from its original mount and place it higher, through a jackshaft or other tricks. Whether what he suggested is feasible, that's another matter altogether - probably not, as Vas commented in his post #11.

Btw, as an aside, in a s/t the hole in the transom is nowhere near 150mm (or whatever the tunnel size is: I'd rather guess 250 or so, for a 13hp motor), because it's only a shaft that has to pass through it.

Apropos, Deleted User: that's another potential water ingress point...

 

[Bouba]

If you box in the motor fully is it not possible to fit an electric fan from a car radiator in the box?

 

[simonfraser]

Why are you assuming that, J?
My swim platform stays bone dry underway, at least in decent sea conditions, and I'd expect the F630 to behave similarly.
I guess it might not be the case with your boat, but there's a big difference in this respect between platforms built above the hull vs. overhanging.

That aside, I wouldn't be surprised if the rudder stock bearings wouldn't leak one single drop when static, but let some water in while cruising, particularly at speed. Torsional forces on rudder shafts of a P boat are pretty substantial, underway!

not familiar with your steering setup, my steering bearing leaked with the wash of the tide or motor running in reverse.
mine has a grease nipple, once it was all unblocked its now dry.
has the grease washed out of your new bearing ?

 

[Portofino]

That has nothing to see with what PF suggested (as I understoood), i.e. unbolt the motor alone from its original mount and place it higher, through a jackshaft or other tricks. Whether what he suggested is feasible, that's another matter altogether - probably not, as Vas commented in his post #11.

...

Correct, mount the electric motor part remote .
Hang it above , way above the current water level in the box .
Fit on top of it little roof mini gazebo clip on , to protect if from any mysterious water drips from above .
Forget chasing your tail looking for leaks or worrying next time you open the lid possibly finding JFM s little sub box design full of water and a yet another dead motor .
It does not matter then how much or where any water gets in the regular OEM bilge pump deals with that in the normal way and there’s the whole air circulation for cooling like OEM .

Use alloy L in x section frames , mini mechano to build the motor mount .
Find a connection solution - belt , chain n gears ... hey nick some parts from a mountain bike like a gear set that INCREASES
The efficiency of a straight 1 to 1 drive connect ,
Google mini corden shafts etc etc .
Mini hydraulic set up = fit the pump to the now remote motor and the drive bit on the BF - connect with hoses accept a bit of loss .This solves any alignment issues involving belts / chains / shafts .

There’s 101 ways of potentially connecting the rotating motion of the now bone dry remote motor to the existing through the hull fitting once the motor is separated .

Any works .

 

[Portofino]

Just one of the 101 ways to connect the motor to the BF housing

https://www.ebay.co.uk/itm/BMW-MINI...e:Mini&hash=item1ec8e52fb0:g:YTEAAOSwNkJaPDm4

 

[Elessar]

That has nothing to see with what PF suggested (as I understoood), i.e. unbolt the motor alone from its original mount and place it higher, through a jackshaft or other tricks. Whether what he suggested is feasible, that's another matter altogether - probably not, as Vas commented in his post #11.

Btw, as an aside, in a s/t the hole in the transom is nowhere near 150mm (or whatever the tunnel size is: I'd rather guess 250 or so, for a 13hp motor), because it's only a shaft that has to pass through it.

Apropos, Deleted User: that's another potential water ingress point...

What you are saying is not true for any of the thrusters I’ve seen. And I’ve fitted 10 or so.
The tunnel is outside the boat. The gearbox/motor bolts to the tunnel in the same way it does to a bowthruster tunnel. The motor/gearbox is then half in /half out of the boat. You can’t remote the motor because it has to be bolted to the tunnel.

 

[MapisM]

Oi, I didn't say you can!
I just said that this is what (in my understanding) PF suggested.

 

[Elessar]

Oi, I didn't say you can!
I just said that this is what (in my understanding) PF suggested.

I was challenging your statement that the hole is nothing like the tunnel size - it is!

see diag

 

[Elessar]

I was challenging your statement that the hole is nothing like the tunnel size - it is!

see diagView attachment 80251

And I know it's a big hole as I once put the hole in the wrong boat. That was an oops moment and another story.......

 

[Portofino]

What you are saying is not true for any of the thrusters I’ve seen. And I’ve fitted 10 or so.
The tunnel is outside the boat. The gearbox/motor bolts to the tunnel in the same way it does to a bowthruster tunnel. The motor/gearbox is then half in /half out of the boat. You can’t remote the motor because it has to be bolted to the tunnel.

When you take the motor off you normally see the shear pin .
I don’t understand why you can’t split ( with a few Oz ,s of ingenuity not 1/2 Oz btw ) the motor and mount it where ever above the blue water line of ingress un bilge pump able swill able water sloshing around .

This Vetus as an illustration is already sat on a post .
Just move it up and away from water inside and reconnect .

 

[Elessar]

When you take the motor off you normally see the shear pin .
I don’t understand why you can’t split ( with a few Oz ,s of ingenuity not 1/2 Oz btw ) the motor and mount it where ever above the blue water line of ingress un bilge pump able swill able water sloshing around .

This Vetus as an illustration is already sat on a post .
Just move it up and away from water inside and reconnect .

You're right in a way, but there is no way you can "just" move it up, the forces are large. You are also introducing a gearbox or CV joint into the system.
They could manufacture one with a right angle gearbox or even a flexible joint which would give installation flexibility but as there are relatively few sternthrusters sold I can't see that happening any time soon.
As it is a bow and stern thruster is identical. So one lot of design costs etc.

 

[Croftie]

When you take the motor off you normally see the shear pin .
I don’t understand why you can’t split ( with a few Oz ,s of ingenuity not 1/2 Oz btw ) the motor and mount it where ever above the blue water line of ingress un bilge pump able swill able water sloshing around .

This Vetus as an illustration is already sat on a post .
Just move it up and away from water inside and reconnect .

Sorry but to me moving the motor wold be a no no.
It would look like a bodge
It would need substantial mounting to withstand a 13hp motor stop/starting/reversing direction
The drive system is just adding more complexity and points of possible failure/problems
Would not be cheap to do.

Far easier would be a 3 sided box that is sealed at the bottom and the vertical edges but could be removed. A lid that can be removed with 2-3 holes on the 3 side verticals near the top for ventilation.

But this is a bit of closing the door after............. Find how the water is getting in, my guess is coming up the rudder stocks

 

[simonfraser]

+1 But this is a bit of closing the door after............. Find how the water is getting in, my guess is coming up the rudder stocks

have you tasted the water yet ? salty ?

 

[kashurst]

a half decent engineering workshop could make an adapter for that with two or three big gears in it to give you the required height.
you would need the dimensions of the existing motor shaft and the motor mounting bolt centres. Two pieces of machined aluminium, lower gear with stub axle at the bottom with bearings either side, lip seal on the output side, intermediate gear on axle running in bearings, topmost gear on axle running in bearings with input socket for the motor shaft to engage. liquid gasket the two halves together with some gearbox oil inside. You can buy stock gears, bearings etc easily. Just need a CAD jockey to draw it up.

Another idea, if the hull in the main lazarette is lower than the stern thruster compartment, is it possible to create a drain from the stern thruster compartment into the lazarette and pump out any water from there instead where it (hopefully) isn't doing any harm.

 

[Elessar]

a half decent engineering workshop could make an adapter for that with two or three big gears in it to give you the required height.
you would need the dimensions of the existing motor shaft and the motor mounting bolt centres. Two pieces of machined aluminium, lower gear with stub axle at the bottom with bearings either side, lip seal on the output side, intermediate gear on axle running in bearings, topmost gear on axle running in bearings with input socket for the motor shaft to engage. liquid gasket the two halves together with some gearbox oil inside. You can buy stock gears, bearings etc easily. Just need a CAD jockey to draw it up.

Another idea, if the hull in the main lazarette is lower than the stern thruster compartment, is it possible to create a drain from the stern thruster compartment into the lazarette and pump out any water from there instead where it (hopefully) isn't doing any harm.

All so Heath Robinson. Just build a dam! Even a box is better than these daft ideas.