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[Murmanseld]

Anyone have some helpful advice on the best way to free a seized prop shaft on a ‘bought’ Maggie M model boat which has been laid up for some years.

[john44]

Hi, is the shaft sized solid or is there movement?
If you remove the coupling and motor to gain access to the shaft
you could try tapping the end of the shaft to knock out the bottom bush.
If it works use the shaft to knock out the top bush, re bush and renew the shaft.
If it fails heat the prop shaft outside the boat, slowly and carefully,
 Protect the hull with wet cloths. I use a plumbers heat resistant mat.
I Then use a small blow torch To heat up the shaft. Clamp the shaft with grips or pliers and
try to rotate the shaft, when you feel movement remove the heat and draw out the shaft.
using a twisting movement.
Works every time for me


John

[malcolmfrary]

emove stuff from the ends like pro and couplers, give the exposed bits a shot of penetrating oil, leave for a few hours, a few gentle taps on one end or the other with a persuader should break the seize.  When it does move, strip and clean.  If the bearings have seixed to the shaft, they might come out with it. 
Depending on the state, a new shaf and bearings might be needed, or even complete relacement. Several threads on here about the best way to replace a complete shaft assembly.

[Murmanseld]

John and Malcolm, many thanks to you both for helpful tips. Hope I can free it up as do not want to go for replacement - just want to get her in the water as quickly as possible. Do any of you two have any recommendations as what rc gear is best these days. Would like to add working lights, rotating radar, a sound card (?) for more realistic diesel engine sound and a speed controller. Sorry these likely sound pretty basic questions but whilst I've built static models in the distant past I never ventured near rc until now. Also have a second fishing boat that would be good to work off the same controller if that's possible..? Thanks

[malcolmfrary]

RC gear these days is mostly 2G4. 
This has the plus side that it doesn't need crystals for tuning/selecting the radio channel, and it costs relatively a lot less than the equivalent gear from just a few years ago. 
It has the downside that manufacturers can lock you in to their brand.  Most of it is aimed at aircraft  That doesn't stop it working with boats, but the instructions usually need a lot of translation to make them useful.
If you want a lot of functions, that will mean enough channels on the set, which will cost more.  Most makes, you can bind as many receivers as you want to one transmitter.  Best to have a look at questions, suggestions and comments in the radio section.  You might find that your questions, both the immediate ones and those you haven't thought of yet, are in there.

[john44]

Hi again, regarding radio gear, most of the sets now are 2.4 G to do throttle,rudder,sound and radar and whatever
else you would want to operate from the tx..
There is a good range about nowadays, it depends on how much you want to spend.
Check how much the receivers are for the set you choose some can be quite expensive.
I personally would not buy a set with less than 6 channels.
As already stated have a look at the radio section on mayhem.
Read reviews on the model you finally decide on.
On some models the instruction manuals are on line so you can have a read through them
to see if it will suit your needs.


John

[Murmanseld]

Malcolm / John many thanks again to you both for good advice and will check out the radio section on the site before deciding on what to go for. A final question (for now!) regarding the battery which came with the boat - a Power Sonic 12v Sealed Rechargeable battery, model PS-1270. The battery is old and doesn't hold its charge any longer so I planned to buy another of the same type as the previous owner thought they were good batteries that lasted longer than the more modern ones - any thoughts/advice on that as still a good buy? Thanks

[malcolmfrary]

When any SLA battery has been left unattended, it will die.  Yours sounds like an industry standard capacity (from the 1270, probably a 12 volt, 7AH type).  Have a look on the Component Shop site - you should find one the same size and shape.
I your boat, a lead battery makes sense, it has the right characteristics at fairly low price and doubles up as the required ballast.
Going for NiMH of the same capacity and voltage would almost certainly cost a lot more while needing extra ballast anyway.  But generally easier to look after.

[Murmanseld]

Thanks again Malcolm, advice much appreciated.

[Peter Fitness]

Adding to what John and Malcolm have said - I use SLA batteries exclusively in all my boats and have found them to be very reliable. One important thing to remember is to always store them fully charged. This piece of advice was given to me many moons ago, so I make a habit of putting my batteries on charge as soon as I return home from a sailing day. One of my batteries died recently, but it was ten years old, so I won't be making a claim under warranty


Peter.

[Murmanseld]

Hi Peter, many thanks for that very useful tip. John

[Geoff]

I do the same but recently I lost three lead acid batteries despite ad-hoc charging. Voltage was fine but under load the 6v batteries went down to 3v on one and 0.88v on the other! The 12v went down to 6v so basically all done. On checking they were 4 years old and for my applications I typically drain them every time I use them.


I was surprised how much battery costs have gone up though!


Cheers


Geoff

[Colin Bishop]

and for my applications I typically drain them every time I use them.

That could be your problem. The further you discharge any lead acid battery the more likely you are to damage it. I believe that even deep cycle batteries should not be discharged more than down to 20% of their capacity and as a rule of thumb 50% is the usual safety norm fora decent life which is why lead acids should only be considered to have a working capacity of half their nominal capacity unlike NiMH cells which can deliver virtually all their rated capacity without damage.

There is an exception with SLAs in the form of Cyclon cells which have a different construction and are much more tolerant of deep discharge. They also retain their charge for longer.

Colin

[malcolmfrary]

What Colin said - Lead Acid need to be kept charged.  Either periodically recharged or float charged will maximise its life expectancy.  Capacity can be checked by a test discharge under controlled conditions and noting how long and at what current subsequent recharging happens. 
Leaving one discharged just lets the acid rearrange the chemistry on the plates to the point where recharging is no longer possible.  I used to be able to quote the chemical formulas for the surface coatings of the plates in their various states, but I've had almost 60 years to forget them after having sat the exam.
Old type open cells "could" be reformed with the right procedures, but a sealed cell is sealed for life - once its dead there is no way short of rebuilding in an appropriately equipped factory it to bring it back to life.

[Akira]

One additional quick note about SLA's. because they are sealed, they can be mounted in any manner that fits, BUT they should always be charged with the vent in the upright position. This will allow any gas build up to vent out. The vent is a small 3 mm or so gap in the seam of the top of the case. It is not a bad idea to remove the battery from the model to charge it, as well.