Stern Thruster “Thruster Tunnel”

[LindaFlorida]

Hello, we are thinking about installing a stern thruster on our 2009 34T Mainship.
The question that we have, has anyone installed the optional exterior thruster tunnel?

The stern thruster that we are interested in is the “Side-Power Sleipner SE100 / 185T Power Thruster”. There is an optional housing unit that covers the exterior props…. Not sure if we really need this housing. Was hoping someone has experience with not having the housing and if the thruster still works ok?

Also the thruster has a $1,600 upgrade option, It’s a thermal protection. I believe that this might be needed if you have a gasoline (vapors) engine? We have a Diesel engine and the bilge area where the new thruster is being installed is dry.

Thank you,

 

[Mambo42]

I have a thruster tunnel for the stern thruster. Am happy with it and it provides extra safety. The stern thruster is close to the swim platform and even though it should not engage by itself, there is always the odd chance.
On top of the the thruster tunnel does protect the stern thruster against debris in the water and it also makes it more efficient.

 

[jleonard]

I had a hydraulic stern thruster on my Albin that was exposed and it was never a problem. Nothing got caught in it. It could not start up accidentally.
I liked it being exposed as I could scrape growth off easily.
Can’t address the efficiency comment as mine worked well enough.

 

[Comodave]

I put a Sidepower stern thruster on our previous boat. It had a tunnel as standard. Actually you couldn’t install it without a tunnel. On our current boat I put in SideShift bow and stern thrusters. They have exposed props and work fine.

 

[LindaFlorida]

Comodave, Interesting that you could not install the SidePower without the tunnel. I contacted the manufacturer with the same questions that I asked on this forum.

Hopefully they will answer if we have to install the tunnel.

Thanks

 

[O C Diver]

I don't know whether you could or couldn't install it without the external tunnel, but it should certainly have more thrust with the tunnel acting like a kort nozzle.

https://en.m.wikipedia.org/wiki/Ducted_propeller

Ted

 

[Comodave]

I don’t see how you sould mount a Sidepower without the external tunnel. That is what seals the water out of the boat.

 

[sickatea]

Flex Seal. According to the commercials, you could build a boat with it.

Sorry Dave, couldn't help myself. Nice to have you back!

 

[Comodave]

Flex Seal. According to the commercials, you could build a boat with it.

Sorry Dave, couldn't help myself. Nice to have you back!

I have seen the commercials but have never tried it. Wonder how it would compare to a good marine sealant.

 

[DDW]

The thruster tunnel is to prevent ventilation I believe. If the props are too close to the surface they suck air. The PO of my boat had the stern thruster installed without the tunnel initially and felt it was not very effective. They then added the tunnel and he said it made a large difference in thrust. 1st hand hearsay anyway.

 

[twistedtree]

Hello, we are thinking about installing a stern thruster on our 2009 34T Mainship.
The question that we have, has anyone installed the optional exterior thruster tunnel?

The stern thruster that we are interested in is the “Side-Power Sleipner SE100 / 185T Power Thruster”. There is an optional housing unit that covers the exterior props…. Not sure if we really need this housing. Was hoping someone has experience with not having the housing and if the thruster still works ok?

Also the thruster has a $1,600 upgrade option, It’s a thermal protection. I believe that this might be needed if you have a gasoline (vapors) engine? We have a Diesel engine and the bilge area where the new thruster is being installed is dry.

Thank you,

I would ask for a copy of the stern thruster installation manual. It's referenced in the general installation manual, but not on their web site.


I did see a note saying that the prop and leg need to be fully inside the tunnel in all installations. I don't think the stern thruster tunnel is optional for any installation. They just sell the thruster and tunnels separately because there are stern and bow tunnels, different lengths, etc. But you need a tunnel.


The $1600 options must be a miscommunication of some sort. All electric thruster motors are thermally protected and will automatically shut off if they overheat. So the option is for something else. Perhaps a fancier control, or perhaps and ignition proof relay for gas boats as you speculate. If you have a link to whatever the option is, we can probably shed more light on it.


The installation manual will be a good cross check of what you need, and what a correct installation should include. Assume any installer doesn't know what they are doing until they have demonstrated that they do.

 

[Pete Meisinger]

I think I would go with the tunnel effect, primarily to prevent cavitation but another reason would be winter storage. Just having the unit hanging on your stern seems sort of vulnerable to theft of the prop or the whole unit and might invite problems during wrapping or tarping.

pete

 

[LindaFlorida]

Here is the response from the manufacturer: “ I would suggest the IP version of the SE100 for your stern thruster because the IP version gives the thruster water resistance protection. If you have any water in your bilge and hit the throttles all the water will come to the stern and possibly ruin the stern thruster.
Please feel free to ask any questions you may have.
Hope this helps “

 

[LindaFlorida]

TwistedTree, I looked up the manual. Yep the “Tunnel” was mentioned 57 times. Thanks for that!!

 

[CharlieO.]

Here is the response from the manufacturer: “ I would suggest the IP version of the SE100 for your stern thruster because the IP version gives the thruster water resistance protection. If you have any water in your bilge and hit the throttles all the water will come to the stern and possibly ruin the stern thruster.
Please feel free to ask any questions you may have.
Hope this helps “

That is not gonna happen in my boat.

 

[DDW]

The tunnel in question here isn't one bonded through the hull (like a bow thruster typically has) if I am not mistaken. These stern thrusters are added onto and hanging out behind the transom and are fairly close to the surface. It is really a shroud with the openings biased downwards so that it will tend to suck up water, not air. It isn't installed in the hull, but around the thruster props aft of the hull.

The response from the manufacturer is nonsense, it refers rather to waterproofing the motor inside the hull and has nothing to do with the props outside the hull. It looks like this. Unless I've completely misunderstood.

 

[LindaFlorida]

After reading the SidePower manual, the tunnel does not come with the thruster. I now understand that there is a tunnel and also separate wings. I was confused, I thought they were one in the same. I do not believe that I need the deflector wings. Well, unfortunately the tunnel is not included. The tunnel without the wings cost a whopping $520.00 on Defender Marine.

 

[Bacchus]

Linda,
There are a couple of options from SidePower but I have no idea what pricing is for them.
I tried to explain exactly what Mainship installed when stern thruster was selected as an OEM option or added by a dealer. I even provided pics of the external installation in your other almost identical thread.
https://www.trawlerforum.com/forums/showthread.php?t=65933

MS did NOT use the IP version...,I have never had a water issue and not heard of it being an issue w other 34T/HT owners. The compartment I described where it is installed has a small bilge pump and that might be something to consider vs a $1,600 option that is only "water resistant" and otherwise unnecessary w diesel power ( nothing else in the ER is ignition protected)

SP does offer a proportional thruster but if your bow thruster is on/off I don't know if mixing types is possible or recommended as the controls may be different and not convenient to have only one proportional and the other on/off.
AFAIK ALL thruster have a thermal overload feature if they are pushed for extended constant operation vs pulsed use.
Again AFAIK the stern tunnel is req'd and not optional. It is listed & priced separate from the thruster as the same thruster serves both bow & stern but the tunnels req'd are very different for B&S. The optional part is the "cowlings" (wings as you call them or top side tunnel extensions). These are purchased separately and simple bolt on. You could just go with them as MS OEM did or go without and see how they perform. The cost is likely nominal and IMO they provide some ptotection from sucking branches etc into the tunnel. They do need to be removed for prop removal, periodic maintenance etc and fairly easy on/off.

My philosophy and effort has been to do everything I can to have a dry bilge. Not to say I never get any water ingress but with the dripless packing the only water I've gotten is rain / wash water via rub rail / hull / deck joint and I address and solve the root cause vs accepting water ingress.