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1 inch prop on 25mm prop shaft?

9K views 12 replies 11 participants last post by  ReefMagnet 
#1 ·
Lost my prop last weekend. After hours of swimming in cold water, it looks like I'm going to have to buy a prop. Can I install a one inch bored prop on a 25mm shaft? Where do I find the right metric prop nut and anode for the old metric prop shaft on my 1972 Dufour Arpege. I'm in the Tampa Bay Area.

Thanks,
Lawson Mitchell
 
#2 ·
It's not a good idea to put the wrong size prop on the shaft. The tolerances are close with a proper fit and you risk losing another prop if you try to fudge it. If you're buying new, any local propellor repair shop will be able to supply one with the proper bore.
 
#3 ·
What is more important is the angle of the taper. Find out if the 1" prop has the same taper as you your shaft .

If it has the same taper then the only point to note is it might sit nearer the small end of the taper but there should be no problem.

the taper of some imperial props is 1 in 12 and the taper of some metric ones is 1 in 10 however if you have a 1 in 10 shaft and prop or a 1 in 12 shaft and prop then it should work for you. A good machine shop could alter the taper in the prop to fit.
 
#4 ·
I fitted a 1'' prop to 25mm shaft and dually lost it,though I did stop the motor twice running over heavy kelp at night coming into harbour, I was lucky in that because I hadn't put her into reverse to clear the kelp I managed to motor into the marina and lost her when I put her into reverse or neutral inside the marina, no damage, dived for hours-never found it.on the good side I replaced with a kiwi prop,briliant.
 
#6 ·
The difference is .4mm. Not too much of a difference. The taper has a greater significance, but the keyway takes a lot of the force. The nut should be metric though. I would use a readily available cheap 1'' prop until I could find a better overall prop, during haul out.
 
#7 · (Edited)
The taper is the problem, you will not get the prop to seat.

Running with a loose and or out of balance prop will cause damage, possibly very considerable damage to the shaft, the cutlass bearing, shaft seal, maybe the P bracket and maybe even the gearbox. Please don't do it.

Especially as the price for a new prop WILL BE THE SAME regardless of the shaft size and taper.
 
#10 ·
Mixing SAE & Metric is a mugs game. It's bad enough when you have both types on the same boat or car but to mix them on the same piece is asking for it - they are NOT the same, even though they get close some times.
 
#11 ·
as long as both pitches are the same ( I mean the pitches of shaft and hub, not the prop pitch ) you are fine. To find out, blue print them. If it matches up you are good to go, if not go shopping again.

ATB

michael
 
#12 ·
Lawson, there should be plenty of machine shops in the Tampa area that can make it work. They shouldn't have to move a lot of metal to make such a slight change.

But for the past 20 years or so, "Metric" has been spoken in most of the US, even in places like Tampa. You should be able to get the right prop and save a fast hundred bucks in machine shop work. And if no one local has what you want?

I'm afraid to joke that you can buy the prop on Amazon.com after all, they have everything else there. (sigh) But I'd still bet that buying the right prop and having it shipped in via Priority Mail or UPS is going to be the fastest, cheapest, AND most reliable solution. If not from Tampa, there may be a prop shop in Jax, FLL, or Miami and those are all overnight shipments via UPS ground, no big deal. They habla lots of metric in Miami.
 
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