Small Prop as Temporary Solution

[Pendragon35]

I have an Albert 35 with a Yammer 3gm30F engine, the standard transmission which I believe is Kazakh 2.1. The prop is an aperture in the rudder. The shaft is .75 in.

Last summer, I discovered I'd lost a blade on my 3 blade prop. After many false starts, I finally had a diver get the prop off, went to a prop manufacturer who recommended a 14R14. The one that came off with was a 13R, not sure of the cup. In the event that's what I bought, from Millers Island Props in Baltimore. It's a thing of beauty. But when the diver attempted to put it on, it would not fit. We've tried lots of things, it's just no go short of dropping the rudder, which I'm not prepared to do.

So I'm going to buy a 13R prop at some point. However, I'd really like to get sailing. Last week I bought a 2 bladed 12R7, a little prop, because it was cheap and immediately available.

My question is: is this ok to use with the Yammer 3GM30F? I know it's not big enough, I know the boat won't go very fast but I just need to get in and out of the marina and get back to at least day sailing while I work on getting a bigger prop.

Things I already know and don't need discussed:
1. 2 blade vs 3 blade - I'm going to get a 3 blade for the final
2. folding props - won't fit
3. I can sail without an engine - no, my marina is such that I can't get out that way without endangering others
4. drop the rudder - just no, not doing that

Thanks for any/all helpful comment!

[smith8273]

I'm not experienced in this, so I should just shut up -- but -- I can't see a problem... everything is a compromise. I would say to be sure to monitor the engine and make sure it doesn't labor or overrev.

[DougR]

Sure, you can use the undersized two blade as a temporary prop. Of course you won’t have the thrust and cruising speed that you used to have, but you know that already.

I think I might ask Millers Island if they have a 14” used prop,( or whatever fits the aperture) or call around to the other prop shops and see what they have available. Or maybe Bacon Sails and used marine stuff in Annapolis. If you’re going to put os something temporarily you might as well try to get as close as possible to the optimum prop.

[Pendragon35]

Originally Posted by DougR

Sure, you can use the undersized two blade as a temporary prop. Of course you won’t have the thrust and cruising speed that you used to have, but you know that already.

I think I might ask Millers Island if they have a 14” used prop,( or whatever fits the aperture) or call around to the other prop shops and see what they have available. Or maybe Bacon Sails and used marine stuff in Annapolis. If you’re going to put os something temporarily you might as well try to get as close as possible to the optimum prop.

I'm definitely calling Millers and I've been to Bacon Sails, that's where I got the small two bladed prop.
thans for the reply

[hpeer]

A question for Millers. If the final prop will not fit in the apature will it be too close to the apature to work properly? IOW is there a minimum clearance you need between the til of the blade and the aperture?

As to prop size you will be able to over rev the engine. So just be mindful of your RPM.

[Kettlewell]

As to prop size you will be able to over rev the engine. So just be mindful of your RPM.

This. Lots of boats spend their whole lives with props that are too small and/or don't have the proper pitch. The engine doesn't care as long as it is within its rpm range. Think of all the engine hours done not in gear, essentially with no prop on there. Pushing your sailboat will present plenty of load. Just don't over-rev it.

[RaymondR]

Sound like the "boss" on the new prop is longer than the old and will not fit between the rudder and the end of the prop shaft. If you were able to know the shaft forward to enable the prop to fit into the aperture could you get the nut on?

It's a diesel and the governor should prevent the engine from over revving.

[Lee Jerry]

Originally Posted by Pendragon35

I have an Albert 35 with a Yammer 3gm30F engine, the standard transmission which I believe is Kazakh 2.1. The prop is an aperture in the rudder. The shaft is .75 in.

Last summer, I discovered I'd lost a blade on my 3 blade prop. After many false starts, I finally had a diver get the prop off, went to a prop manufacturer who recommended a 14R14. The one that came off with was a 13R, not sure of the cup. In the event that's what I bought, from Millers Island Props in Baltimore. It's a thing of beauty. But when the diver attempted to put it on, it would not fit. We've tried lots of things, it's just no go short of dropping the rudder, which I'm not prepared to do.

So I'm going to buy a 13R prop at some point. However, I'd really like to get sailing. Last week I bought a 2 bladed 12R7, a little prop, because it was cheap and immediately available.

My question is: is this ok to use with the Yammer 3GM30F? I know it's not big enough, I know the boat won't go very fast but I just need to get in and out of the marina and get back to at least day sailing while I work on getting a bigger prop.

Things I already know and don't need discussed:
1. 2 blade vs 3 blade - I'm going to get a 3 blade for the final
2. folding props - won't fit
3. I can sail without an engine - no, my marina is such that I can't get out that way without endangering others
4. drop the rudder - just no, not doing that

Thanks for any/all helpful comment!

"...not sure of the cup." - I assume you mean pitch. It would be nice to know for comparison.

With respect to fitting the recommended prop, have you (your diver) tried turning the rudder to one side?

As to the main question, as long as it is "temporary" (a very ambiguous term), I would think it would be OK to use the smaller prop for a short while. The over-revving could be a concern (and should also be governed by the engine, as RaymondR said), but I have two others. First, the engine will be lightly loaded, so be sure to run it "at speed" to get the temp up. Second, and probably most importantly, maneuvering will be compromised (perhaps a lot), so be careful the first couple of times docking as the response to the throttle will be much slower than you may be used to with the old prop.

[Wotname]

Originally Posted by Pendragon35

..........
Last week I bought a 2 bladed 12R7, a little prop, because it was cheap and immediately available.

My question is: is this ok to use with the Yammer 3GM30F? I know it's not big enough, I know the boat won't go very fast but I just need to get in and out of the marina and get back to at least day sailing while I work on getting a bigger prop.................

It is OK as a temporary measure. It won't harm your engine in the short term.

[Pendragon35]

Originally Posted by Lee Jerry

"...not sure of the cup." - I assume you mean pitch. It would be nice to know for comparison.

With respect to fitting the recommended prop, have you (your diver) tried turning the rudder to one side?

As to the main question, as long as it is "temporary" (a very ambiguous term), I would think it would be OK to use the smaller prop for a short while. The over-revving could be a concern (and should also be governed by the engine, as RaymondR said), but I have two others. First, the engine will be lightly loaded, so be sure to run it "at speed" to get the temp up. Second, and probably most importantly, maneuvering will be compromised (perhaps a lot), so be careful the first couple of times docking as the response to the throttle will be much slower than you may be used to with the old prop.

Yes we've worked hard at getting the rudder over. No go. The top end operating rpm on the engine is 3,600 and I've only had it up to that running it in neutral. And yes, you're right, cup is wrong, pitch is right, thank you.

[boatpoker]

Originally Posted by Pendragon35

Yes we've worked hard at getting the rudder over. No go. The top end operating rpm on the engine is 3,600 and I've only had it up to that running it in neutral. And yes, you're right, cup is wrong, pitch is right, thank you.

Propeller cup is not the same as pitch.
https://www.miwheel.com/propeller-cu...9Ccup%E2%80%9D.

[skipperpete]

For a kickoff, ¾” is pretty slender for a 3GM 30 propshaft unless its Aquamet or some similar alloy, I don’t recall ever seeing a ¾ shaft even on much smaller engines. The bigger issue is getting the taper and key to match and being able to easily get it all snugged up correctly underwater….. and knowing that its fully engaged on the taper, not getting this right will at the least mean vibration and at the worst, loss of the prop.

[Fore and Aft]

Raymond R has the right idea. If you have a coupling between the engine and shaft removing that might give you enough room to slide the shaft forward so you can squeeze the prop in place.
I would be more worried about the keyways matching, shaft taper being correct and there being enough thread for the prop nut to engage properly.
Cheers

[RaymondR]

Since you have the old prop off you should be able to do a side by side comparison to check whether the taper and diameters and keyway dimensions are the same.

[Pendragon35]

Originally Posted by hpeer

A question for Millers. If the final prop will not fit in the apature will it be too close to the apature to work properly? IOW is there a minimum clearance you need between the til of the blade and the aperture?

As to prop size you will be able to over rev the engine. So just be mindful of your RPM.

Good question, I'll find out.