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[andyn]

I've had this for a while sitting in a spares box, and have realised it may be useful. So I cleaned it up and polished it, but I have no idea what size it is. I think it's a Mocom prop, judging by the tailcone. It is stamped, however it's very hard to read, and even if I could read it I don't understand Mocom numbers...

Maybe Ian, Danny or W3bby could help? It's 44mm diameter.

[bogstandard]

That looks very much like a prop from the AMPS stable, maybe from the early to late 70's, I think they sold them in either bronze or aluminium versions.
The force fitted hub allowed fitment to standard screwed shafts, otherwise they could be sleeved and a drive dog used.

But on the other hand, it is a long time since I handled one. Plus around that time, a prop was a prop was a prop, there was very little difference unless you went for the very expensive American imports like Gale, which were like being from another planet.

Bogs

[omra85]

Bogs is right, it's an Amps prop. Can't remember the number code but if its 44mm diam, it will be the equivalent of around an 1818.
It was used for submerged drive (hence the rounded rear corners) and would probably have been used on a Merco 35 or a Webra 40.
You could possibly still use it on a low powered modern engine such as an SC or ASP.  The thread "should" be 5mm but it could also be 3/16 (UNF?) or more likely 2BA.
Unfortunately hardly an heirloom 

Danny

[andyn]

So would it be any good on a geared .21? (If I get one...) Or possibly geared 7.5cc?

[omra85]

It would work on either - but not well as the revs would be far too high!  Its too small for gearbox use, (even with a geared 21 you will probably need at least 2023 or above).
The main reason I wouldn't use it on anything is that, suppose you spend ages setting the carb, pipe length, mixture, etc for THAT prop - then damage it on a bouy, bank, another boat - what do you replace it with??  Also if you wanted to try one size bigger or smaller, you can't because the range is finished.
Your best bet is to keep it in the bottom of your toolbox "for emergencies"  and use a prop which you can replace with an identical one with known setup.
Course - if you never go racing, you'll never damage it ...   

Danny

[andyn]

Course - if you never go racing, you'll never damage it ...   

Don't mean you aren't going to lose it in the bottom of the pond

Thanks for that, I'll stick it back in the box...

[omra85]

Put a 6mm bit of silicone water tube on your shaft between your coupling and your top bearing (or collet and outer tube end if using a flexy).
Then if the shaft comes out, it won't slide out to the bottom of the lake 
Danny

[andyn]

I've not actually done that one yet, the one that was on the multi at Wiki Park snapped half way down, just after being launched. I think it needed more grease. Problem of course being that Racing Models shafts don't have a tailstop.

[SteamboatPhil]

I've got a prop just like it Andy, used it with a Frog 500 (dates me)

Mines in the bottom of my tool box now

 

[bogstandard]

It does date you a bit Phil, myself as well. I bought my Frog 500 in 1966, cost I think about 3 pounds something (a weeks wages), and was fitted into I think a Veron torpedo boat, with RCS single channel single button radio, with a quick blip for throttle control. Minimite and Minimo servos spring to mind.

I started to use Amps props about 1973/4 time, first with a Merco 61 and tuned internal watercooled home made pipe in a large Huntsman, then with an Arrowshaft with the then mighty OS80, complete with about a pound and a half full sized brass flywheel. As for damaging props, the OS combination would cut thru weed banks and anything else with no damage to the prop all, they were almost indestructable, unlike the stuff they hit.

It was after this heavyweight time I discovered OPS engines and the fantastic (for then) Gale props. They were like precision razor blades mounted onto a hub compared to the Amps offerings.

All now well in the past, but very nice to be reminded of old times and just what sort of things we used to get up to. No such thing as CNC made running fittings then, if you wanted it, you made it yourself.

Bogs

[Martin (Admin)]

I used to visit Miller Agnew (AMPS) in his workshop (Chateris) quite often in the 80/90ties what a great old bloke!
I had one of his hulls, a Chris Craft something I believe.