please help, need quality advice on a difficult prop removal

[morcambedigger1]

hy, ive a mid 80s jaguar25 yacht, with a 14hp lombardini inboard (5-10yr old). the prop I think is the original one,
and is absolutely tiny, a small slightly rectangular sided two bladed affair. Everyone at my club agrees its under-propped, as anyone whos been aboard agrees i dont get enough 'go' from it when the throttles are opened, and well, ive had comments that it reminds people of a wisk!
I presume its a compromise for less drag under sail. Ive been given, very kindly, a larger two bladed one, and intend to fit it, or possibly run to finding 'the right one' ie rt pitch size etc. - how would i suss the rt size?

- but, when i tried with all my might with a large spanner and the gearbox in drive to lock it; to get that single castle nut off the shaft, the thing wasnt budging (pin out of course!)
- i dont want to damage the shaft or gearbox by say hammering it, how do you get a really tough - on prop nut off please? - a torque wrench and plumbers strap maybe?

- Help!

- morcambedigger

[methodman]

it might be a left hand thread? use your thumb nail and try and follow the grooves.

[Discus]

In order to calculate the correct size and pitch for your boats setup, you could use a propcalc programme. You can download one from www.castlemarine.co.uk/pitch.htm . The usual caveats apply when choosing a new prop - 3 blades will give you more 'bite' compared to a two blader but will induce slightly more drag than a two blader. You could also drop an e-mail to T. Norris and supply them with the details of your vessel and they could recommend a prop for your setup ( www.tnorrismarine.co.uk/ ). I had our prop repitched by them last year and the results were very good. Somewhere on the boss of your current prop will be a stamp stating size and pitch, so at least you know what to avoid. To get the prop nut off, try soaking it with penetrating oil for 24 hours. If you have no joy, use a butane blow lamp to carefully warm the nut up. It will expand more quickly than the surrounding metal and should loosen off. If the nut is stuck solid, chances are the prop will have bound on to the shaft too so you may need to beg/borrow a gear puller to get it off (we had to do this). The prop you have been given may well have a different taper and keyway arrangement compared to your current one so may not even fit your shaft. Job definitely worth doing though as if you get it right, it will transform the motoring ability of the boat.

Hope this helps

Rob