A25 19mm Prop Nut

[MikeF]

Has anyone had to replace an A25 Prop nut? After removing and replacing the prop on my 1978 A25, the original bronze castellated (or crown) 19mm nut disintegrated due to it's age. I believe
it's the original shaft in the boat, which was connected to a Volvo MD17C.

I have tried without success to find a replacement nut. Does anyone know where I
can find one...? Even a non-castellated one would do. Perhaps a supplier in Europe?

Many Thanks,
Mike A25 Hornbay
Dallas

[jleonard]

I just bought spares for mine thruMcMaster-Carr online. Mine were standard english threads and stainless, however McMaster carries metric as well. They were also relatively cheap.

[MikeF]

Thanks jleonard - I called McMaster. They don't list a 19mm, but asked for exact measurements. My sample is with a local prop dealer who was trying to locate a duplicate nut. I'll fetch it & contact McMaster again with more exact dimensions. Any further leads appreciated.

[Phoenix27]

Has anyone had to replace an A25 Prop nut? After removing and replacing the prop on my 1978 A25, the original bronze castellated (or crown) 19mm nut disintegrated due to it's age. I believe
it's the original shaft in the boat, which was connected to a Volvo MD17C.

I have tried without success to find a replacement nut. Does anyone know where I
can find one...? Even a non-castellated one would do. Perhaps a supplier in Europe?

Many Thanks,
Mike A25 Hornbay
Dallas

[Phoenix27]

I got a metric nut from a local industrial fastener place,But it was nylonlocking SS fastener nut and I used red locktight on the threads. I had to make a rudder suport fitting and I used a piece !.75X2 inch nylon block and just drilled a couple of holes in it.I tried to buy one but they seem unavailiable .I also had to make two rudder bushings out of Delrin a local machine shop helped with that. ,But I need a drain plug that goes into the bottom of the skeg I'm not sure what size it is. my next project is to make a wideshield .I bought the moulding so I have some idea of what needs to be done Sincerely Phoenix27

[jleonard]

Thanks jleonard - I called McMaster. They don't list a 19mm, but asked for exact measurements. My sample is with a local prop dealer who was trying to locate a duplicate nut. I'll fetch it & contact McMaster again with more exact dimensions. Any further leads appreciated.

Yes get dimensions. I didn't see 19mm listed, so maybe it's really 18 or 20mm. Tomorrow I'll look in my machinery's handbook and see if there is a 19 mm thread that's a standard.

[jleonard]

My machinery's Handbook does NOT list a M19 thread.
M18 x 1.5
M18 x 2.5 should measure about 17.9mm to 17.7mm over the thread OD

M20 x 1
M20 x 1.5
M20 x 2.5 should all measure about 19.9mm to 19.6mm over the thread OD

Basically you are going to measure the thread OD. If it is about .700" it is 18mm. If it measures about .772" or just over 3/4 inch it is 20mm.
The second number is the pitch which is measured thread tip to tip. 2.5 mm is almost .100", 1.5 mm is about .060", 1 is .040" . I would guess it would be the M20 x 2.5.

McMaster-Carr lists nuts in stainless steel

Hope this helps

[MikeF]

Thanks for that research jleonard! Other sources are also convinced of the the non-existence of a 19mm thread. Armed with all this info, I will contact the suppliers afresh.
Thanks again for the help.

[sandro]

Has anyone had to replace an A25 Prop nut? After removing and replacing the prop on my 1978 A25, the original bronze castellated (or crown) 19mm nut disintegrated due to it's age. I believe
it's the original shaft in the boat, which was connected to a Volvo MD17C.

I have tried without success to find a replacement nut. Does anyone know where I
can find one...? Even a non-castellated one would do. Perhaps a supplier in Europe?

Many Thanks,
Mike A25 Hornbay
Dallas

[sandro]

What is the speed of A25 whit Volvo md2b engine,and full rpm on load? I have an A25 with md2b and i am having 1850 rpm on full load going 7.5 knots but i think this is not ok? thanks

[Brian]

Hi Sandro,

Geez, 1850 rpm and going 7.5 knots is great!!! I'm thinking I've got a problem...2400rpm and 6.5 knots? I have a Volvo MD2030 (30hp).

[sandro]

Hi Sandro,

Geez, 1850 rpm and going 7.5 knots is great!!! I'm thinking I've got a problem...2400rpm and 6.5 knots? I have a Volvo MD2030 (30hp).

Hi Brian,I think that this is not ok becouse there is no smoke at full throtle and the engine is not torchering it self at all,and everything is original by albin and they say it should go 8knots