climenuts

Cutlass Bearing & Engine Mount Replacement

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Looking for a sanity check on an engine mount replacement, realignment, and cutlass bearing replacement. As a Mechanical Engineer my practical DIY skills are lacking and I'm a bit intimidated by taking this on myself. Boat's a C&C 29mk2 with a 10° offset prop shaft rigidly coupled to a Yanmar 2GM. Checked archived threads and saw no real reviews on the PYI mounts or alignment methodology.

After 430 Engine Hours and another ~350 hours of fixed-prop spinning sailing since the last replacement my cutlass bearing is toast. Intense vibration, sounds like the shaft is hitting the log, etc. materialized since my last haul-out where everything seemed fine. I replaced the prop during the last haul-out which may have made any previous issues much worse. I reached my torso to the shaft from the dinghy and sure enough there's quite a bit of play at the end of the shaft.

I'm thinking that this much wear this fast must be a a result of an alignment issue. I'm determined to get this job done right this time so I can comfortably go two years between haul-outs and bearing replacements. The engine mounts are without a doubt original.

General game plan is to replace the engine mounts with the boat in the water one at a time using the old mounts to get "close" to the current alignment. I'm thinking I will use the PYI replacements. To re-align I'll de-couple the rigid coupling, center the shaft in the log, and re-align vertically, athwartships, and pitch/yaw using the feeler gauge method. Once the shaft is re-coupled I'll haul the boat (or use our tide grid if I'm brave enough) and replace the cutlass bearing. I plan on biting the bullet and buying the strut-pro tool. With the bearing out I'll have a look at the alignment through the log and strut from the outside of the boat and make sure it looks right; adjusting the alignment again as necessary.

I'll do the stuffing box packing while it's dry. I can't put a flexible coupling without replacing the shaft due to prop/rudder interference. Shaft was straight when I replaced the bearing 2 years ago so I don't want to pull it.

Thoughts and comments welcome. Will post pics of the event when the time comes.

 

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Good luck!  I just did this.  The alignment was almost too easy, especially since I went with new and different mounts. 

I'm wondering if there's a way to check it all once everything is done. 

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21 minutes ago, Leeroy Jenkins said:

I'm wondering if there's a way to check it all once everything is done. 

Feeler gauges between the coupling faces.

The last time I did it the Yanmar spec for a rigid coupling was "withing 0.007" runout". Check your manual to be sure.

Take out the coupling bolts and separate the faces a hair then insert a feeler gauge - I started with 0.003. Slip the faces together over the gauge until it's snug then rotate the shaft taking measurements all round it.

Adjust as required.

The final alignment must be done in the water because hulls change shape slightly when afloat VS on stands.

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28 minutes ago, SloopJonB said:

Feeler gauges between the coupling faces.

The last time I did it the Yanmar spec for a rigid coupling was "withing 0.007" runout". Check your manual to be sure.

Take out the coupling bolts and separate the faces a hair then insert a feeler gauge - I started with 0.003. Slip the faces together over the gauge until it's snug then rotate the shaft taking measurements all round it.

Adjust as required.

The final alignment must be done in the water because hulls change shape slightly when afloat VS on stands.

Not to hijack the thread, but I mean how do you know if the shaft wasn't shifted slightly off center when you started.  I was at .003 when I went in the water. (I used .001" per inch of coupler dia, without a urethane spacer wih an extra .003 overall allowed with a spacer).  

I guess put it in gear and see if water starts pissing in? 

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26 minutes ago, Leeroy Jenkins said:

Not to hijack the thread, but I mean how do you know if the shaft wasn't shifted slightly off center when you started.  I was at .003 when I went in the water. (I used .001" per inch of coupler dia, without a urethane spacer wih an extra .003 overall allowed with a spacer).  

I guess put it in gear and see if water starts pissing in? 

I think he means that you redo or recheck the alignment with the boat in the water.

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27 minutes ago, Leeroy Jenkins said:

Not to hijack the thread, but I mean how do you know if the shaft wasn't shifted slightly off center when you started.

That will show as transverse or vertical variation in the coupler gap. You align it close on the hard and then finalize in the water.

You might get lucky and only need to double check in the water.

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Haul the boat at a real yard that already has the tools to remove/replace your cutlass bearing. Once the new bearing is in, check the alignment of the strut/bearing combo with the stern tube - I'll bet real Loonies that they will NOT line up with the center of the stern tube. (to do this, use wood wedges to hold the shaft in position in the stern tube. Go to strut I examine how the shaft contacts the rubber all around the bearing. If alignment is off it's easily visible). Once proper shaft position is determined, change the alignment of the rubber hose to hold the shaft seal in that position. THEN align engine to shaft.

Just as an illustration - I had to raise a J-120 engine 1.25" to get all to align. Boat had the shaft knocking on the hull exiting the tube as installed by the factory.

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@longy, Couple questions...

1) I'm a bit confused with how I would adjust the alignment between the stern tube and the strut if it's off. I don't recall seeing mounting hardware on the strut and I think it might be glassed on. I would assume I'd take up as much misalignment as possible with the tube and if it's too bad for that... I'd have to look at messing with the strut.

2) What rubber hose are you talking about? The shaft seal connecting the stuffing box and stern tube? I'm assuming I just loosen the hose clamps and adjust it so there's no strain?

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Not so sure the shaft log tube should be used as a guide when there is a strut....yacht construction being what it is... The bore in the strut and fitted cutlass bearing are better alignment guides.

Wedging the shaft in the tube is a clever idea. 
 

Trying to preserve alignment by replacing one mount at a time seems like a dubious idea.  
 

I wouldn’t have the coupling bolts installed during alignment. 
 

If the history of the shaft is unknown it should be checked for straightness...boatyard lift operators being what they are. 
 

Dunno about your access to the adjust the nuts, but I have found it worthwhile to cut a wrench down to a stubby size for adjustment. Seconds with an angle grinder on a cheap wrench has saved much time. 

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2 hours ago, climenuts said:

@longy, Couple questions...

1) I'm a bit confused with how I would adjust the alignment between the stern tube and the strut if it's off. I don't recall seeing mounting hardware on the strut and I think it might be glassed on. I would assume I'd take up as much misalignment as possible with the tube and if it's too bad for that... I'd have to look at messing with the strut.

2) What rubber hose are you talking about? The shaft seal connecting the stuffing box and stern tube? I'm assuming I just loosen the hose clamps and adjust it so there's no strain?

There is no 'adjustment' of the strut or the shaft log. So you get the shaft as centered as possible thru the bearing (reduces wear a lot) and deal with where it ends up going thru the shaft log. You want the shaft seal to sit evenly on the shaft with the rubber hose not stressed in a bend - you get this by letting the hose move about until the outer piece of the stuff box sits nicely centered on the shaft, than clamp the hose in place. Rotating the hose back & forth helps it adjust to a centered position.. Don't worry if the hose doesn't align with the log when your done, getting all the tight fitting bits flying in line is the goal. The hose just keeps water out & holds the seal from rotating

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1/ don't do this on a tidal grid. You won't have time

2/ find a yard with a cutless bearing tool rather than buy a one time use tool

3/ my Yanmar 3GM30F was installed by me, including the shaft log and strut. I got >1800 hours before the cutless bearing needed replacing. So yours failing so quickly suggests alignment is way out.

4/ Shaft logs should never be assumed to be aligned. The builder drills an oversized hole and glasses in a glass tube. Roughly accurate yes, but not centered perfectly. Ignore it unless the shaft is really close to the edge making a stuffing box not able to seal.

5/ Adjust the engine to the shaft coupling i.e. up/down + left right. You need to support the inboard end of the shaft before you attempt to connect it to the gearbox coupling. Figure out the overhung load that is supported by the gearbox bearing (basically half the shaft weight + coupling weight). Use a spring scale to support the inboard end of the shaft near the coupling. You're a ME so that should be trivial. You're replacing the gearbox bearing temporarily with this support to account for the shaft drooping. You can do it by feel, but it's more of an educated feel so for a first timer get a fishing scale.  

6/ Use a feeler gauge between the coupling faces. 0.001" per inch of coupling diameter. That's 0.004" for a 4" Yanmar coupling. You probably will have to sand off surface rust on both faces. Check at 12/3/6/9 o'clock. You probably can visualize things in 3D pretty easily. If the gap is bigger at the top you need to raise the front of the engine. If the gap is bigger on the right, the engine needs to swing right.

7/ At the same time use a metal edge ruler on the coupling edges to make sure they are parallel. Check at 12/3/6/9 o'clock (if possible; 6 might be too close to the hull)

8/ The PYI R&D soft mounts are fine. Adding a soft coupling would be better still if you had room. The mount height may not match the Yanmar ones so find out the nominal height and working adjustment range.

Because engineers think with pictures, or at least I sure do, here is a pretty picture showing some of these concepts.

image.thumb.png.392fd43a366851c2262f34685f081aeb.png

 

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We replaced our mounts on our 29-2 because two of them were broken and vibration was definitely getting out of hand. Dropping the strut on the boat is no biggie, the last people to do a cutless bearing for the previous owner took off the strut so they could take out the shaft and do the whole thing in the shop.

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@Zonker once this plague has subsided I owe you some beers or a bottle... thank you.

I think I can visualize why the new prop made the vibration worse now that I see your sketch. It is heavier and overhangs the strut a fair bit more and likely lifted the inboard end of the shaft.

I'm failing to see how the scale will be used in this process. Am I trying to support it so it's free to align with the cutlass bearing when hung from a line or am I taking a measurement to apply a load to the transmission coupling to account for the mount deflection?

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Neither - you are trying to reverse the effects of gravity on the shaft. If you just pull the shaft & coupling up to the back of the trans, the weight of the shaft & coupling are bending that end down quite a bit. So the shaft is now slanted through the bearing & low of it's 'straight' location relative the trans. So you are trying to remove that weight from the end of the shaft so it assumes it's natural position vertically. You are trying to align to .001's so this makes quite a difference in the process of alignment

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Calculate the weight of the right hand of the shaft + coupling. Lift the shaft up with the spring scale at this weight so you're supporting the coupling in space. This is where you can do it by feel and just prop up the shaft from below too. Say the shaft + coupling weighs 14 lbs. Now that weight is supported by a bearing that is forward a bit so if your spring hook is a bit aft of the coupling. You'll need to lift up _slightly_ more than 14 lbs because your support is a bit aft of the gearbox bearing. But this isn't too precise. You're just trying to figure out where the shaft wants to be.

The other end, supported in the cutless bearing, will bind as you try to rotate it if it is too low or too high. You can try doing it by feel. Lift it up slowly while turning. There'll be a point where you can feel it bind if it is too high. So lower it a bit.

The phantom line is what it looks like if you don't support the shaft before alignment. The solid line is the ideal position you are trying to establish.

This is all BEFORE you try to slide it forward 1/2" to align with the gearbox coupling. You may find that your engine is way too high or too low and you've been basically bending the shaft under way and wearing out your cutless bearing.

Picture your gearbox attached to the phantom line (sagging shaft) position. Do you see how the shaft is curved? That will be the shape it will take while running. It will wear the bottom front and upper aft end of the cutless bearing instead of it evenly.

 

image.thumb.png.2c1249571a2e7af0d73fdde27d8d488c.png

This weight would be normally supported by the gearbox bearing. But the gearbox bearing is (temporarily) not there (because you have slid the shaft slightly aft so the couplings are not touching). 

This is a reasonable explanation:

https://www.zfmarinepropulsion.com/wp-content/uploads/The-Ins-and-Outs-of-Engine-and-Shaft-Alignment-Part-I.pdf

 

image.png

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That's very clear, thanks.

I've reached out to a local shaft shop to see what a new shaft would cost just in case the shaft isn't straight. If I need to get a new one I'll shorten it by a couple inches and get a flexible coupling. Maybe if it's "cheap" I will just do the flexible coupling anyway. I'm a bit afraid I didn't pull the old prop off evenly during the last haul-out and may have bent the end of the shaft.

 

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Oh, don't be surprised if you can't get the coupling off and you have to cut the shaft anyway

 

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Just now, Zonker said:

Oh, don't be surprised if you can't get the coupling off and you have to cut the shaft anyway

 

Yeah.. I had it off two years ago when I last replaced the bearing and it was a real pain in the ass.

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If you had it off 2 years ago good chance you can get it off again. Did you face the coupling to make sure it was perpendicular to the shaft?

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:rolleyes:... I definitely did not - I recall a bit of violence was required to get the damn thing back on... In hindsight it was a bit of a clothes hanger abortion last time around and I'm paying the price for it now. I didn't check to make sure the key wasn't interfering with the taper fit or check any alignment whatsoever. Ran more smoothly right after the replacement but got up to its old tricks on my desolation trip last summer and has been horrible since the prop replacement.

Depending on the price to buy a new shaft I may just bite the bullet and get a flex coupling and shorter shaft, face the shaft coupling, and do a complete job of it. At the very least I'll make sure the key isn't interfering with the fit and make sure the clearance/alignment doesn't change when the shaft is rotated per your link to make sure the coupling is perpendicular.

You eluded to a local shaft guy, Ross, earlier. Is he someone you'd recommend and where's he working out of?

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IF the shaft is in good condition you can just cut a new taper on it and shorten it. In that case you'd want a fatter flexible coupling (to make sure the new machining doesn't interfere with old taper/threads)

To test the fit you can blue the shaft and install the coupling and check the fit. 

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Right. I've been working 16 hour days this week to meet a deadline so I am a bit slow on planning for this at the moment. Should be able to dig into it over the weekend. I don't think the taper and threads are suitable for shortening the shaft unless a get a really thick coupling but there isn't a whole lot of room.

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This might have been previously mentioned ... do your final alignment when the boat is in the water with normal backstage tension 

 

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backstage = backstay, but yes agreed.

For re-machining the coupling position - you're basically only losing the depth of the threaded part with the nut. So maybe ~1 shaft diameter. Assuming your shaft has a nut holding the coupling on of course.

image.png.30f22d000e8898f7e52da7a74f0b72a6.png

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@Zonker Coupling doesn't have a nut it has a taper, grub screws, and key IIRC. The guys at Bracewell said they need to order in the stock but will setup both tapers & blue them to ensure a proper fit, face the coupling, etc. If the old shaft is straight I'll look at shortening it with them.

Any opinions on PYIs dripless shaft seals? If I'm redoing everything between the transmission and prop I'm considering putting one in to replace the current stuffing box.

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I had one. I liked it. Fit a hose clamp in front of the s.s. collar to act as an extra backup if the doubled set screws ease out. Flooded our engine compartment because I didn't tighten them enough for first install. First I noticed one of our transoms was about 12" deeper than normal and the engine was labouring, pouring out black smoke. It did not like having the V-belts underwater but kept runnng.

Sometimes you have to overcompress the bellows a bit more than they specify to apply a bit more pressure - otherwise my feathered prop would flex the shaft in rough seas and it would leak slightly (we're talking big seas not like PNW stuff)

https://vmdafoe.com/ are the local experts on shafts for decades and will likely have in stock anything you need, but I'm sure Bracewell will be fine too. I had somebody at Shelter Island machine a coupling for us and match it to the shaft, but don't recall who it was.

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When I changed my cutlass bearing the shaft was worn enough where it met the bearing that it had to be replaced also.It actually had flat spots worn into it. Really strange but with a new shaft the boat ran very smooth after replacement. I would plan on replacing the shaft.
At the same time you could add a damper between the engine and shaft to take out the minute vibrations. You could also add a dripless seal instead of the stuffing box.
It will make you sleep better at night
BTW, I like spending other peoples money.
 

 

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9 hours ago, woodpecker said:

When I changed my cutlass bearing the shaft was worn enough where it met the bearing that it had to be replaced also.It actually had flat spots worn into it. Really strange but with a new shaft the boat ran very smooth after replacement. I would plan on replacing the shaft.
At the same time you could add a damper between the engine and shaft to take out the minute vibrations. You could also add a dripless seal instead of the stuffing box.
It will make you sleep better at night
BTW, I like spending other peoples money.
 

 

Thanks... it is looking like everything between the transmission and the prop is going to be replaced at this point. Ran the dripless seal past the admiral this evening and she said "if it's just a few hundred bucks let's just do it".

Luckily these purchases have happened contemporaneously with a 90 hour workweek so my "OT" will pay for it :wacko:

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1 hour ago, climenuts said:

Thanks... it is looking like everything between the transmission and the prop is going to be replaced at this point. Ran the dripless seal past the admiral this evening and she said "if it's just a few hundred bucks let's just do it".

Luckily these purchases have happened contemporaneously with a 90 hour workweek so my "OT" will pay for it :wacko:

The Volvo Penta shaft seal is cheap , very simple and reliable 

https://www.generalpropeller.com/pdf/Volvo Penta Shaft Seal Installation Instructions.pdf

 

 

 

also remember that shaft seals  dry out when you haul out and must be bled when the boat is floated 

this bleeding procedure requires that your shaft seal  have good  access 

consider this when selecting a shaft seal system 

 

C76AA6E7-8E65-451A-90E9-C73FB40EB335.jpeg

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I replaced my mounts two years ago, 

I disconnected the shaft coupler, then wound the entire engine up to the top of the existing mounts, then took each one out and fitted it's replacement. Once all four were in I lowered it back into position. (Boat was on the hard)

Alignment with a feeler gauge was not too difficult. She purred like a kitten after that. A few weeks later I did a second alignment after the boat had been floating for a while and had settled, barely any difference in alignment required. When I disconnected the shaft, I made note of how much it dropped at the coupler, then shimmed it back up to that height when I went to reconnect and realign it all. Did a bunch of eyeballing and it all seemed to work out ok.

One interesting thing I learned, Port and Starboard mounts were different, 150 vs 200 or something like that, to account for the torque loading from the engine, one side simply feels more load on the mount than the other. So Keep an eye out for that small detail.

Side bonus, my shaft seal stop dripping like a son of a bitch after all that. (One of the reasons I looked at replacing the mounts in the first place)

Oh yeah, I did not wind down my mounts tight to the hull until I had the engine lowered and roughly in place. I had marked with Sharpie the exact footprint of the old mounts but leaving the mounts floating a bit left me a bit of left right wiggle room for the whole show. I did the final tighten on mount to hull connection once the left right alignment was really starting to dial in. The new mounts did not align precisely with where the old ones had been for whatever reason. Don't really care why, it runs smooth now.

157970869_Yanmarmounts-01.jpg.5cf2825dc175842bdc697b6905218f70.jpg

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Yah, motor mounts don’t last forever 

motor-sailing,  poor alignment , jumbo alternators  wear them faster   

Mounts are cheap and simple to replace 

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@slug zitski This is the first I've heard of shaft seals requiring venting when the boat is floated. I haven't done anything particularly special to my traditional stuffing box and it seems to do just fine. The PSS Dripless seal by PYI has a vent hose which I assume serves the purpose of flooding the seal for lubrication.

I'm a bit skeptical of anything that claims to be "cheap, very simple, and reliable" but I'll look at more than the PYI dripless seal I have been looking at. Part of the appeal of the PYI system is I can order replacement engine mounts, the shaft seal, and the flexible coupling from the same place. PYI also seems to have good feedback for customer service and support.

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PYI seals now include a hose - it can either be led up above waterline or connected to positive pressure raw water to eliminate the requirement to manually "burp" the air out of the seal

 

Altho I do have a personal connection at PYI, their customer service is excellent

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Not sure I saw it anywhere, but first thing is make sure your shaft isn't bent.  Uncouple block at packing as best you can to center and do a runout with a dial indicator on the machined side of the coupling flange.  If the shaft is out nothing will fix.  I did our engine instal and beds, it's not to hard you just need lots of patience.  You want to clear everything out of the way you can exhaust etc to have easy access to all the mounts. Also if the engine sits at a incline it's not a bad idea to try and ballast close to horizontal of possible. The weight of the engine can be a pain trying to get square. I used a RND soft coupling and am pretty happy with it.  You still want to try and hit .003 at least but it gives you a little wiggle room.

 

Also on the PYI seal if you are using in warm water disregard there speed spec for vented or flushed.  It will get hot in warm water if only vented even at low speed.  I plumbed ours via a isolation valve into the engine raw water intake.  Have not had any issues since.

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6 hours ago, slug zitski said:

C76AA6E7-8E65-451A-90E9-C73FB40EB335.jpeg

Since you've posted this Volvo Penta schematic, two questions:

1. That looks like my set-up, and the conical piece between items 2 and 4 is the rubber drip seal. (Mine doesn't have that ring labeled 4)  Dumb question, but if I'm getting too much "drip" I can control that by tightening the bracket bolts slightly on bracket 1, right?

2. The forward-stbd engine mount is corroded and looks bad, although I'm not having excessive vibration. Would I have to perform an elaborate re-alignment process if I just change out the front mounts?  

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Part #4 is just for installation of the unit, it is removed once shaft is in place.  I don't think there is any adjustment, altho you do need to inject more grease occasionally

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3 hours ago, longy said:

Part #4 is just for installation of the unit, it is removed once shaft is in place.  I don't think there is any adjustment, altho you do need to inject more grease occasionally

Yes 

 

it’s an installation tool to protect the shaft seal ... remove and store 

Pinch the gland with your fingers to air bleed 

use a small syringe full of grease to inject lubricant 

lubricant will last a whole cycle , re lube  when hauled for your next antifoul 

It is a very simple and reliable solution that lasts for thousands of hours 

 

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