Propeller Play/Movement?

[Scherbacj]

Should my propeller have a small amount of movement fore/aft? Or should it be completely snug with no movement? 
 

I have a new boat with about 6 trips on it, and I just noticed that there is a tiny bit movement or play fore/aft or front/back. I know some bearings and stuff are supposed to have a small amount play to account for thrust, etc. but is that how an outboard propeller should be? Or should I snug up the prop nut a little more? 

[Capt Ed]

The new Mercury quiet propeller hubs have some fore and aft movement.  

[Way2slow]

Many of the props today use and adapter so they can make one prop fit several motors.  If the movement is just where it's moving on that adapter, I wouldn't be too concerned.  If however, it's the actual prop shaft moving back and forth in the lower unit, then I would be getting concerned.   There should be not movement of the prop shaft in the LU other than rotational, unless it was made in China, then all bets are off on how it's made.

[WRB]

Not knowing the make or size the prop shouldn’t move in/out on the shaft splines.

I used a 12” length of 2x 4 wood under the cavitation plate to keep the prop from rotating when tightening the prop nut until the nut was tight. The lock washer has tabs to fold over the hex out flats. Tighten the nut and align the hex nut flats to 2 tabs and fold the tabs up to prevent the nut from loosening.

Tom

[Scherbacj]

It’s a Mercury Spitfire 4 Blade 13.4” x 15P and I believe it has the FloTorq 2 Hub.Attached is a picture from my owners manual that shows all the pieces.  It does use some sort of adapter piece and a thrust washer based on the Owners Manual. It seems like the propeller is moving slightly back and forth on the hub adapter piece. I can’t tell

for sure, but it seems like the propeller and part “D” are moving back & forth on part “B”. It’s hard to tell though so the prop might be moving and part “D” might be staying still. When I push it all the way forward, the Nut Retainer has a little play in it so I think part “D” is also moving. That makes me think I might need to tighten up the nut a little. But I guess since you have to line the nut flats up with the retainer tabs, you might have to back the nut off a little and make that retainer be slightly loose, right? 
 

It’s definitely not the shaft moving in and out of the lower unit. At most, it would be the adapter moving back & forth on the splines, but I’m pretty sure it’s the prop moving on the adapter.

 

I just remembered last time I was out I was in a narrow cove and the wind blew me back into a underwater tree or rock. It wasn’t very hard, and there are no marks or scratches anywhere from on the prop, cav plate, skeg or anywhere so I can’t even tell where exactly it hit. I caught it right as I was about to hit and engaged the trolling motor so it wasn’t like a hard slam, but if the whole weight of the boat hit right on the propeller I could see the possibility of it damaging the thrust washer. I just can’t remember if that play was there to begin with. 
 

I guess tomorrow I will just pull the prop off, inspect the thrust washer, if it looks okay I’ll re-install it per the instructions and tighten the nut to the proper torque spec. If it still has a little play at least I’ll know that it was installed correctly. 

 

[gim]

1 hour ago, Scherbacj said:

I guess tomorrow I will just pull the prop off

 

I take the prop off routinely during the season to ensure there isn't any debris in there that isn't supposed to be.  Do the same with the prop on my bow mount.

 

Old fishing line can do a number on both of them.

[Jigfishn10]

I’m not a mechanic but I thought props had to be tightened by a torque wrench to a specific specification? 

[J Francho]

4 minutes ago, Jigfishn10 said:

I’m not a mechanic but I thought props had to be tightened by a torque wrench to a specific specification? 

Yep. Better get a prop wrench. They're plastic. Torque rating is about 40 lbs., or basically snug.  The plastic prevents going any higher. 

[Capt Ed]

Your propeller nut requires 55 lb-ft. of torque.  Use a torque wrench. The thrust washer should be snug after you torque properly.  If the tabs do not line up in the center if the flats, you should tighten until they do with a torque wrench.  Always add torque, do not reduce below requirements.  .  

[Scherbacj]

After looking at more closely it’s a combination of the two. A little movement of the prob on the hub adapter, and a little movement of the shaft. But after doing more research that’s normal. I put a torque wrench on it at 55ft-lbs and it clicked without moving the nut so it’s at least to spec. 

[Scherbacj]

2 hours ago, Scherbacj said:

After looking at more closely it’s a combination of the two. A little movement of the prob on the hub adapter, and a little movement of the shaft. But after doing more research that’s normal. I put a torque wrench on it at 55ft-lbs and it clicked without moving the nut so it’s at least to spec. 

I decided to pull it off, and I think when I put the torque wrench on it the first time I must not have had the locking tabs flattened out enough because when I went to take it off, it required almost no resistance. I took it all apart, inspected it, and put it back on, torqued it to 55ft-lbs, and then had to torque it a fair amount more to align the tabs. But now it has zero slop, just the tiniest amount of shaft movement which is normal based on all my research. I guess that’s probably why they say to re-torque it after the first couple uses. 

[Capt Ed]

Just to double check, you bent the two tabs  up against the lock nut tabs, not down?

[Scherbacj]

13 hours ago, Capt Ed said:

Just to double check, you bent the two tabs  up against the lock nut tabs, not down?

 I bent them down when removing it, bent them back up after checking everything and retorque of the prop. 

[TnRiver46]

Hmm I’ve never used a toque wrench for a prop, I must have the magic touch. I also don’t have many horsepower so maybe it doesn’t matter ? Running a 16 yr old engine and it runs perfectly so I’m not terribly concerned 

[J Francho]

That assembly diagram looks nothing like mine.  Merc 50 4 stroke w/ Bigfoot LU.  Spec says 40 lbs.  I've never dragged my torque wrench out it's case for this since I have a Merc prop wrench.  I keep it in the boat.  This looks exactly the same as the last four Mercs I've owned - a 90, 115, 2.5 L  ProMax, and this 50.

 

[Scherbacj]

6 hours ago, J Francho said:

That assembly diagram looks nothing like mine.  Merc 50 4 stroke w/ Bigfoot LU.  Spec says 40 lbs.  I've never dragged my torque wrench out it's case for this since I have a Merc prop wrench.  I keep it in the boat.  This looks exactly the same as the last four Mercs I've owned - a 90, 115, 2.5 L  ProMax, and this 50.

 

Yes, it’s a different hub system. I’m obviously not an expert, but from what I have seen you might have a FloTorq 3 or 4 Hub system whereas I have a FloTorq 2. The only reason I used the torque wrench was to make sure it was done properly since I didn’t do the initial install. As it turns out, the torque wrench wasn’t very helpful anyhow because when I reached the suggested torque the nut and locking tabs were nowhere near lined up so if I had just tightened the nut until I felt it was tight and then lined it up, I probably would have ended up in the same place. 

[J Francho]

Is this a smaller motor?  All of mine have had torque master lower units except the pro max, which had a sport master. I've seen different set ups on older motors too. Our old stern drive actually had a cotter pin. 
 

At any rate, a prop wrench and a spare hub are must haves in my boats. I've even carried a spare prop at times. 

[Swamp Girl]

I try to establish a firm grip on my canoe paddle.

 

 

Wait, that wasn't the least bit helpful, was it?

[TnRiver46]

15 hours ago, Scherbacj said:

if I had just tightened the nut until I felt it was tight and then lined it up, I probably would have ended up in the same place. 

That’s how I do it 

[Jigfishn10]

On 11/25/2024 at 4:49 PM, TnRiver46 said:

Hmm I’ve never used a toque wrench for a prop, I must have the magic touch. I also don’t have many horsepower so maybe it doesn’t matter ? Running a 16 yr old engine and it runs perfectly so I’m not terribly concerned 

It’s probably because you’ve been doing for so long you have that mind muscle connection to know how tight the nut needs to be. I don’t take on mechanical work enough to have that connection. 
 

Happy Thanksgiving

[J Francho]

I don't think it's as critical a spec so much as it is to prevent difficulty in removing the prop.  The retainer keeps it from coming loose.  Anytime I stayed at a camp site or motel with my boat, I always removed the prop, along with the graphs and tackle, before letting the boat out of my sight.   

[TnRiver46]

2 hours ago, Jigfishn10 said:

It’s probably because you’ve been doing for so long you have that mind muscle connection to know how tight the nut needs to be. I don’t take on mechanical work enough to have that connection. 
 

Happy Thanksgiving

Right back at ya. 🦃 

 

I’m too hillbilly for mind muscle connection, I just figure there are a lot of threads so I tighten it until it’s tight, never had one come off 😂 

 

now I have hit a rock and broken a prop trying to drive thru rapids, would not recommend 

[Jigfishn10]

I’ve been navigating the same bay since 2010 and thought I knew it like the back of my hand. I went out at low tide, every thing AOK, saw the point of and island continuing on below the water, checking electronics, looking overboard…everything AOK….until it wasn’t AOK and bottomed out damaging my prop. Know exactly what you mean @TnRiver46!  
 

I got really good at reconditioning the prop at the mooring with dingy tied off to the boat’s transom