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Old 25-03-2013, 19:34   #1
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Hurth HBW 250

Hi folks-

this should be an easy one. I have a Hurth HBW 250 transmission on my new (to me) boat. it is coupled to a Perkins 4-154 which seems to run very well.

my question is about the transmission. do I need to be careful about free-wheeling (letting it spin) the shaft while under sail? There is a fixed 3 bladed prop (for now), so there will be significant torque and drag on the shaft.

DO I drop it in reverse like some transmissions to lock the shaft, or is it always a free-wheeling transmission?


thanks-

bg
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Old 25-03-2013, 20:08   #2
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Re: Hurth HBW 250

freewheel, it is just a gearbox, it don't know if the engine is running or not
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Old 25-03-2013, 20:25   #3
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Re: Hurth HBW 250

Quote:
Originally Posted by NSboatman View Post
Hi folks-

this should be an easy one. I have a Hurth HBW 250 transmission on my new (to me) boat. it is coupled to a Perkins 4-154 which seems to run very well.

my question is about the transmission. do I need to be careful about free-wheeling (letting it spin) the shaft while under sail? There is a fixed 3 bladed prop (for now), so there will be significant torque and drag on the shaft.

DO I drop it in reverse like some transmissions to lock the shaft, or is it always a free-wheeling transmission?


thanks-

bg
with the engine off, put it in reverse to stop the prop. or in neutral to freewheel. never put it in forward. with the three blade, faster to have it freewheel while sailing. change the oil in the tranny every 100 hours. do you have the water cooler on it? good investment!
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Old 25-03-2013, 20:38   #4
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Re: Hurth HBW 250

Hey - thanks for the replies! very helpful. why never leave it in forward? ...Just curious. so I get now that it's a purely mechanical, non-hydraulic gearbox, unlike the Newage PRM's and Borg Warner's I'm used to.

it does have the cooler bolted to the side of it, but it is clear that no hoses were ever hooked up to it. This boat is going north, and will be in cold water probably for most of the rest of its life... do I really need to hook up the cooler? it has thus far been in Florida waters, with no problems reported by the previous owner. however, judging by the scant 900 hours on the engine (over 23 years) I don't think it's really seen a lot of use.

reg-

bg
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Old 26-03-2013, 06:06   #5
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Re: Hurth HBW 250

sailr69 gave you the correct advice, follow it. If you leave it in forward the gear will still turn and wear out the forward clutches.
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Old 26-03-2013, 08:30   #6
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Re: Hurth HBW 250

Please explain about the clutches. If it is in gear, nothing turns unless the engine is spinning also. Prop just locks in place and increases drag.
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Old 26-03-2013, 08:38   #7
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The hurth boxes use torque generated by the engine to compress the clutch pack. In fwd with no torque applied the clutch discs are in contact with each other but not really closed. This will allow the prop to spin and wear the clutch.

In the astern position the prop provides the torque to keep the clutch engaged, however the clutches will not be as thoroughly engaged as they would with the engine running.
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Old 26-03-2013, 09:40   #8
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Re: Hurth HBW 250

Operation instructions advise that sailing with engine off and gear box in forward can result in serious damage.

Reverse (locking the propeller) or neutral are both OK - your preference.
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Old 26-03-2013, 10:24   #9
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Re: Hurth HBW 250

Thanks, learned something today
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Old 26-03-2013, 11:13   #10
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Re: Hurth HBW 250

Me too!
thx
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