Sternthruster problems - advice?

[Deleted User YDKXO]

In the 5yrs I've owned my current boat I have had recurring problems with the sternthruster, specifically failures of the electric motor and electrical control box attached to it. The control box has been replaced and the motor rebuilt but now it seems the motor has failed again and it is beyond repair. Both my bowhruster and sternthruster are Sidepower units and have the same 13.1hp motors. I have never had a problem with the bowthruster so I know there is no inherent problem with the motors

The problem with the sternthruster is that the motor sits at the aft end of the boat (obviously!) in a separate bilge compartment under the bathing platform

This compartment always has water sitting in it despite my best efforts to keep it dry and obviously any water tends to migrate to the aft end of the compartment when the boat is on the plane. This means that the sternthruster motor is often sitting in water or being splashed with water. No wonder it keeps failing

There are 2 questions I wanted to ask

First, I approached Osmotech in the UK (Sidepower agents) for their advice. They suggested I replace the standard motor with an IP motor ie one that is protected from moisture. Unfortunately Sidepower do not offer a like for like IP replacement for my 13.1hp motor and Osmotech have offered a 10hp motor but suggested that it will give similar thrust to my existing 13.1hp motor if I also replace the existing 4 bladed prop with a new 5 bladed one. I'm not sure I believe this. Any comments?

Second, I want to make further efforts to keep this bilge compartment drier. I have already replaced the hatch seals and the rudder stock bearings and I am really at a loss to understand where the water is coming from now. The mechanic who replaced the hatch seals swears blind that the new seals are not leaking because he's sat inside the compartment with the hatch closed and had somebody else spray water over it. There is no sign of any leaks from the rudder stocks either. There is quite a large bilge pump in the compartment but it cant empty all the water. I am thinking about fitting an additional small bilge pump to get more of the water out but that still doesnt tell me where its coming from. Any ideas? There is no connection between this compartment and the engine compartment forward of it

 

[markc]

Hi Mike, I have the same problem with water sitting in the same place and am also not sure where the water is coming from. I had assumed it was excess rainwater, but the hatch seals are OK. The 2 thoughts I had were 1 - a weep around one of the bolts that joins the platform to the hull (unlikely) or 2 - I know the water from cockpit drains around the engine hatch run through the BP and out the the back, and maybe there is a leak from here.

My stern thruster looks to be in a similar position to yours and is boxed in - i think it's a Vetus unit, and haven't had any problems caused by moisture, but I'm not sure on their power rating, or quality!

 

[Richard.C]

Is there any way to build a small enclosure around the stern thruster to prevent the water moving/splashing on the motor?

 

[BartW]

fwiw,
this summer I've replaced the old and broken 4 blade propeller from the bow thruster
with a new 6 blade prop,
6 blades is now standard at Vetus, they don't claim anything about the thrust, they claim (and it gives) less noise compared to the 4 blade.
my feeling is that the thrust is the same, for sure not more then before.

regarding the moisture,
boxing the existing motor seems a good solution

do you really need a stern thruster ?
I don't have it never missed it

 

[Elessar]

In the 5yrs I've owned my current boat I have had recurring problems with the sternthruster, specifically failures of the electric motor and electrical control box attached to it. The control box has been replaced and the motor rebuilt but now it seems the motor has failed again and it is beyond repair. Both my bowhruster and sternthruster are Sidepower units and have the same 13.1hp motors. I have never had a problem with the bowthruster so I know there is no inherent problem with the motors

The problem with the sternthruster is that the motor sits at the aft end of the boat (obviously!) in a separate bilge compartment under the bathing platform

This compartment always has water sitting in it despite my best efforts to keep it dry and obviously any water tends to migrate to the aft end of the compartment when the boat is on the plane. This means that the sternthruster motor is often sitting in water or being splashed with water. No wonder it keeps failing

There are 2 questions I wanted to ask

First, I approached Osmotech in the UK (Sidepower agents) for their advice. They suggested I replace the standard motor with an IP motor ie one that is protected from moisture. Unfortunately Sidepower do not offer a like for like IP replacement for my 13.1hp motor and Osmotech have offered a 10hp motor but suggested that it will give similar thrust to my existing 13.1hp motor if I also replace the existing 4 bladed prop with a new 5 bladed one. I'm not sure I believe this. Any comments?

Second, I want to make further efforts to keep this bilge compartment drier. I have already replaced the hatch seals and the rudder stock bearings and I am really at a loss to understand where the water is coming from now. The mechanic who replaced the hatch seals swears blind that the new seals are not leaking because he's sat inside the compartment with the hatch closed and had somebody else spray water over it. There is no sign of any leaks from the rudder stocks either. There is quite a large bilge pump in the compartment but it cant empty all the water. I am thinking about fitting an additional small bilge pump to get more of the water out but that still doesnt tell me where its coming from. Any ideas? There is no connection between this compartment and the engine compartment forward of it

I Used to fit sternthrusters Mike and we used to build a dam around them as Richard suggests as a matter of course. It's the only way IMO. The operation of a bilge pump float switch is a foreseeable event no matter how many seals you replace and you don't want it to cost you a k (ie a new motor!)

Just epoxy in some marine ply or some GRP offcuts if you can get them. About 6" high will do the trick as your pump will be shouting at you long before that's inadequate.

 

[vas]

boxing it in, wont it create heat dissipation issues?
OK, it's stern so wont be used alot, but still, no?

I recon cheapest solution would be a hydraulic pump on the PTO on one of your engines, 2 pipes to stern and modify the housing to accept a hydraulic motor

cheers

V.

 

[Deleted User YDKXO]

boxing it in, wont it create heat dissipation issues?

That was my concern but if Elessar says its OK I will do that. I dont use the sternthruster a lot. Its more a nice to have rather than essential but I hate having anything on the boat which doesnt work!

I cannot imagine that a hydraulic solution would be cheaper although if I was speccing a boat from new I would certainly go hydraulic

 

[BartW]

That was my concern but if Elessar says its OK I will do that.

pls realise that Elessar proposes the smart solution to make a "dam" = wall around the motor,
not a fully enclosed box,
then, heat is no isuue, I'm just not 100% sure if this is enough protection against moisture "spray" inside that compartment

 

[vas]

I cannot imagine that a hydraulic solution would be cheaper although if I was speccing a boat from new I would certainly go hydraulic

I'm pretty sure the "motor" you'd have there would be really peanuts (couple of hundred euros?) The PTO adapters etc is another mater though

pls realise that Elessar proposes the smart solution to make a "dam" = wall around the motor,
not a fully enclosed box,
then, heat is no isuue, I'm just not 100% sure if this is enough protection against moisture "spray" inside that compartment

+1


cheers

V.

 

[Portofino]

When on the plane and bouncing about .....
1- May the rear box section flexes and looses it static seal your guy tested out ?
2- the lid move and thus water ingress ?

Fix
Is there any way of mounting the motor higher ( accept the water ingress in a chasing tail kinda way ) ......
Longer shaft , belt n pulley , chain n sprockets ?
I,am writing this without the benefit of a pic of the existing set up / arrangement in the box .

 

[vas]

When on the plane and bouncing about .....
1- May the rear box section flexes and looses it static seal your guy tested out ?
2- the lid move and thus water ingress ?

sounds reasonable (and difficult to sort ...)

Fix
Is there any way of mounting the motor higher ( accept the water ingress in a chasing tail kinda way ) ......
Longer shaft , belt n pulley , chain n sprockets ?
I,am writing this without the benefit of a pic of the existing set up / arrangement in the box .

this I doubt is feasible, we are talking 13hp motor, moving it and mounting it even 200mm away is going to be pure engineering hell I recon (pulleys double v-drive et al..)

 

[jfm]

Ref box or dam - I prefer box, with a top lid made of perspex screwed on and sealed, so you can see into the box to check for water.

The problem with a dam is that if the seal for the big deck hatch is leaking underway (which is 99% for sure the problem) then the leaking water, if coming in directly above the box, could fall into the box and fill it up, thus totally killing your new motor.

So fit a box, and don't worry about heat. IMHO

 

[spannerman]

Most thruster motors have an inbuilt overtemp sensor which will shut them down if they get too hot. The other alternative is the external sternthruster which is a sealed housing which just bolts to the transom, I have fitted many if these and its a simple installation, obviously you will need to fill the existing hole but its a totally waterproof thruster.

 

[simonfraser]

show us some pics of this compartment, its either from above or below that the water is getting in ....

 

[vas]

show us some pics of this compartment, its either from above or below that the water is getting in ....

+1

also, would the water level rise (or if wiped, appear) even when the boat is left in the marina for say a month (and a dry one preferably)?

 

[Deleted User YDKXO]

show us some pics of this compartment, its either from above or below that the water is getting in ....

Sorry if I had a pic like that I would have posted it. Unfortunately I’m not on my boat at present. All I can say is that the motor is horizontal below the cover in the photo

 

[Elessar]

That was my concern but if Elessar says its OK I will do that. I dont use the sternthruster a lot. Its more a nice to have rather than essential but I hate having anything on the boat which doesnt work!

I cannot imagine that a hydraulic solution would be cheaper although if I was speccing a boat from new I would certainly go hydraulic

The box doesn’t have a lid on it. It’s just a 6” or so high dam. Maybe higher depending on config but not lid.

 

[MapisM]

I have already replaced the hatch seals and the rudder stock bearings and I am really at a loss to understand where the water is coming from now.

Does the hatch get washed while cruising?
If not (mine doesn't, unless in very rough seas), any water ingress from the hatch can only be due to rain or boat wash.
Either ways, sorting your doubt is as easy as tasting the water, I reckon!

 

[Elessar]

Ref box or dam - I prefer box, with a top lid made of perspex screwed on and sealed, so you can see into the box to check for water.

The problem with a dam is that if the seal for the big deck hatch is leaking underway (which is 99% for sure the problem) then the leaking water, if coming in directly above the box, could fall into the box and fill it up, thus totally killing your new motor.

So fit a box, and don't worry about heat. IMHO

Just seen this. All the thrusters I’ve done have not had a hatch above so a lid has been pointless.
If there was a potential water source above a hood yes but sealed no.

They are whopping motors. If you are using it until the thermal cut out trips you are either terrible at boat handling or in some sort of big pickle.

If you seal it in it will cut out sooner and take longer to reset.

You may never overheat it even in a box, but you don’t want to find out you’ve made it worse if you are in a pickle.

Just IMO.

 

[Elessar]

When on the plane and bouncing about .....
1- May the rear box section flexes and looses it static seal your guy tested out ?
2- the lid move and thus water ingress ?

Fix
Is there any way of mounting the motor higher ( accept the water ingress in a chasing tail kinda way ) ......
Longer shaft , belt n pulley , chain n sprockets ?
I,am writing this without the benefit of a pic of the existing set up / arrangement in the box .

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