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[Edward Pinniger]

Last summer I bought one of the ready-to-run RNLI Severn lifeboats (this was actually what got me interested in R/C model boats in the first place). I ran it several times on local ponds and it ran perfectly; I was careful to clean up + dry the lower hull after running it and make sure no water got in the battery compartment.

However, today I decided to give it a test run as it hadn't been run for about 6 months, and discovered that one of the motors had burnt out/corroded due to water leakage around the prop shaft (or the seam between the two halves of the pod). Since it has twin-prop steering with no rudder, this makes the boat useless unless you want to run it in circles 
The RTR Severn has "pod" motors - in sealed (supposedly!) plastic pods beneath the hull, rather than having motors inside the hull. Quite a few RTR boats are like this; the "Tornado" MTB from the same manufacturer as the "Smasher" destroyer is another example. This setup seems to be much more prone to water damage than the usual one, as there is very little distance between the prop shaft exit and the motor itself.

I had exactly the same problem with another RTR boat - the "Pelican" US Coast Guard lifeboat - but assumed this was just due to shoddy manufacturing quality, it only cost £20 new! The Severn, on the other hand, costs about £50 (luckily I got mine second-hand for much less) and is produced in association with the RNLI; I'd expect better from a product like this!

Short of completely replacing the motors with proper in-hull ones (not an easy task) does anyone have any ideas for how to prevent this happening? I've thought of using epoxy glue (or similar) to cover the pod in an attempt to seal the seam in the pod moulding, then apply plenty of grease to the prop shaft exit. Dismantling the pods is not possible without taking the entire boat - including wiring - to bits, due to the way it is assembled (I found this out when attempting to repair the "Pelican")

I may be able to repair the Severn by replacing the defunct motor with the working one left over from the Pelican. However I don't really want to attempt this without having some way of preventing the motor leaking again!

[dan]

hi edward,
have you got any pics?

[Philipsparker]

I'd say that at 50 quid for a second hand boat you had paid over the odds - I don't think thay are much more than that at an RNLI shop where you can be sure the lifeboats are getting some money. There are many places offering them for 30 quid - which probably means a manufacturing price of less than a tenner. That means some will come out of the Chinese factory less than perfect - you get quality or low price but not often both.

Now the good news - replacing the motors is NOT difficult. While doing this you can also put a proper X-tal controlled radio set in. The top unscrews easily enough and ther battery compartment is big enough to offer you quite a choice without having to alter the superstructure much.



There are a couple of threads on Mayhem where people cover this conversion in more detail. I suspect that any of these will be easier than fixing what you have - I bet that spare pod motor isn't a good match speedwise for the one you have for example. Sods law doesn't work in your favour !

On the plus side you will get a really nice boat out of it for relativly little effort. It will be faster (that hull is good and will plane), more manouverable and sailable with other model boaters. Cost will be around 75 pounds (Radio set £35, Speed control £20, Servo <£5, 2 props, motors and couplings). Go for it, you won't be disapointed.

Phil

[Edward Pinniger]

hi edward,
have you got any pics?

This is what I mean: (see attachments below)
I don't know what the technical term (other than "flimsy cheap shortcut"!) is for this setup; "pod motors" was the term that came to mind as the motors are in sealed plastic housings fitted below the hull.

The third photo shows the lump of rust which the motor has ended up as. It looks like the problem was caused by the prop shaft seal (a greased rubber washer) being missing - this must be a manufacturing fault, the other pod has a seal. The damage is FAR worse than on the Pelican - which just had a bit of water seepage around the seam between the pod halves, causing one of the motor coils to corrode.
I'm going to replace this pod with the working one left over from the "Pelican" and will seal both pods with extra grease around the prop shaft and silicone sealant around the seam + hull join of the pod moulding (I noticed when removing the defunct pod from the Severn that water had collected around the top where it meets the hull; this could end up seeping through to the motor if there's even a slight crack in the seam)


Thanks to Philip for the advice - however (as I've mentioned in previous posts)  R/C boats are a "secondary" interest of mine - I mainly build static display models - and I'm on a rather limited budget, so I try and spend as little as possible (I paid £5 for the model second-hand, not £50 - I was just quoting that as the RRP)- I usually stick to rebuilding/detailing RTR models and using the built-in motors/radio gear without modification. I do have a couple of models that I intend to buy a decent radio set for - one is the Billings Calypso (an eBay bargain) the other is my scratchbuilt steam yacht, which has only cost about £10-15 in materials + fittings to build so far, but has turned out as such a nice model that it really deserves good quality radio + running gear. However I couldn't afford to spend £50-75 on radio gear for everything I build, and if I were going to spend that much I'd probably buy a decent kit rather than a RTR boat to put it in.

I will, however, try and avoid models with "pod" motors in future!

[roycv]

Hi, I had a seized up pod motor in the RNLI boat.  So thinking that there was nothing to lose I took off the propeller and used a pair of pliers to turn the motor shaft.  After a bit it revolved and so I used WD40 on it and then some oil and it has worked ever since.  Perhaps I got there just in time!
Roy

[derekwarner]

Hi....looking at the last motor jpg above.......in both the as shown upper half shell and lower half shell [completer withe corroded motor], neither plastic shells display water or corrosion evidence relative to the motor output shaft

This would indicate that the ingress of water was not around  the motor prop shaft axis....but possibly from the casing joint    ...not sure...but could conclude may be best to strip or split a new POD motor casing & re-glue with a compatable waterproof adhesive.......Derek

[Edward Pinniger]

Hi....looking at the last motor jpg above.......in both the as shown upper half shell and lower half shell [completer withe corroded motor], neither plastic shells display water or corrosion evidence relative to the motor output shaft

This would indicate that the ingress of water was not around  the motor prop shaft axis....but possibly from the casing joint    ...not sure...but could conclude may be best to strip or split a new POD motor casing & re-glue with a compatable waterproof adhesive.......Derek

That was what I originally thought - but as the rusted Severn motor has a missing prop shaft seal, this surely must be the cause of the problem. There was nothing to stop water getting in through the prop shaft, so it had probably been rusting away ever since I first ran it! The fit of the motor against the prop shaft is quite tight, so water must have gradually seeped in and all around the motor (otherwise, it would probably have died after the first run).

As I mentioned previously, I'm going to replace the dead motor with the working one left from the "Pelican", glue the casing halves thoroughly and seal it up with silicone sealant. If this one also bites the dust, the Severn will have to be shelved until I can afford a replacement radio + motors!

I was originally planning to detail + repaint the Severn but never got round to it due to other projects - I'm glad I didn't now as I would probably have wrecked the added detail when dismantling the boat to remove the motor.

[derekwarner]

Hi all....Edward........point taken...the motor shaft could be an austenitic series stainless steel  so hence no corrosion...the next element is an alloy bearing housing that holds a sintered bronze shaft bush ..outboard of this is a void space

These simple Mab*****Ichi type motors were never designed to operate in water so I am not sure where the shaft seal was intended

For corrosion to occur, we also need oxygen

I am not a fan of "silicone sealant" it sticks to everything but the intended critical part .....Derek

[Edward Pinniger]

I found this comment (as a "customer review" on a commercial site), regarding the RTR Coast Guard patrol boat (see my other post)

"As a long time RC Model Boater one learns that there is no boat where the propellor shafts are competely sealed against water getting in . You must after each usuage set the boat up on end take tissue and wrap it around props where shafts join and let water drain out and wick into tissue. Also it is highly recommended to buy a good grade of Wet Bicycle Chain oil, for use in wet enviornments, dropper it into where the shaft comes out of the motor, hand rotate the propellor forwards and reverse to work the oil in . This boat has had problems with wires inside coming un sodered , the deck does remove but its a time consuming process, better to sent it back to NKOK in Los Angeles under warrantee repair. I have had my boat now for about 2 years and with proper care it works just fine, yes water does get into the motor housings , but the oil mostly keeps it out. The smaller scale NKOK USCG Motor Lifeboat model requires similar care.I sail both of these with other model boating friends on a larghe pond all summer long."

I'll try this, and see how long the motors last!

Anyway, thanks to all for the advice.

[Edward Pinniger]

Returning to this subject, does anyone have any spare, unwanted motor pods left over from converting their Severns or similar, which they'd be willing to trade?
I could do with a couple of pairs; one to repair my own Severn, the other to repair the USCG patrol boat - which arrived today and is NOT "as new" as it was sold as, but a complete write-off motor-wise, with one of the prop shafts completely rusted through(!). The radio is OK, so it should be repairable with a new pair of pod motors.