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Old 10-03-2011, 23:50   #1
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Morgan NM 45 Hurth Transmission

My Hurth tranny on our Morgan 454 NM is shot and I am trying to order a new one.I need to obtain the correct transmission gear ratio before ordering the replacement. Does anyone know what Morgan chose for the gear ratio?
The gear box does not show the data and the Morgan factory rep said that all of the old records were destroyed by a hurricane a few years so they cannot help.
Thanks for feedback
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Old 11-03-2011, 18:14   #2
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Re: Morgan NM 45 Hurth Transmission

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Originally Posted by lenganote View Post
My Hurth tranny on our Morgan 454 NM is shot and I am trying to order a new one.I need to obtain the correct transmission gear ratio before ordering the replacement. Does anyone know what Morgan chose for the gear ratio?
The gear box does not show the data and the Morgan factory rep said that all of the old records were destroyed by a hurricane a few years so they cannot help.
Thanks for feedback
Which engine and transmission do you have, and which version of the Morgan do you have?

I had the Perkins 4-108, and can pull the transmission ratio data from the Hurth 150V transmission. The boat itself is the race version, not the cruising one - otherwise known as a Morgan N/M 456 (an IOR two tonner from 1983).

Note that if you actually have the tranmission in hand, and it will rotate, you can work out the gear ratios simply by turning the output side sufficient times to rotate the input side one turn.

- rob/beetle
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Old 12-03-2011, 10:54   #3
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Thumbs up Re: Morgan NM 45 Hurth Transmission

Rob,my Morgan NM 45 is hull #16 and is an IOR hull,deep draft,fin keel,with a cruising interior. Engine is Universal M40 and the tranny is a Hurth HBW 150V.
The prop shaft no longer turns while in gear with engine running,so I cannot figure out how to calculate gear ratios.
We dodged a bullet yesterday when the Tsunami hit our harbor in Honolulu where she is berthed. Thankfully,she suffer no damage.
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Old 12-03-2011, 11:15   #4
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Re: Morgan NM 45 Hurth Transmission

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Originally Posted by lenganote View Post
Rob,my Morgan NM 45 is hull #16 and is an IOR hull,deep draft,fin keel,with a cruising interior. Engine is Universal M40 and the tranny is a Hurth HBW 150V.
The prop shaft no longer turns while in gear with engine running,so I cannot figure out how to calculate gear ratios.
We dodged a bullet yesterday when the Tsunami hit our harbor in Honolulu where she is berthed. Thankfully,she suffer no damage.
The gear ratios on the Hurth 150V on my engine are A 2.13, B 2.22.

The Universal M40 is rated at 32HP, the Perkins 4-108 rated at 50hp; the 150V on my boat has a side-attached aluminum box through which is pumped sea water to cool the transmission - your setup may not require that additional transmission cooler.

If you're going to replace the transmission then you're going to have to remove it from the motor's bell housing - if you do that now you can then rotate the tranmission and work out the existing gear ratios (unless it's welded itself together inside or the clutch plates are gone in both forward and reverse).

Personally I would tend to disregard whatever the original builder did and talk with the engine manufacturer to find out what they would do today - which might be different than what they did when the engine was originally put in the boat.

Good luck.

- rob/beetle


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Old 12-03-2011, 12:11   #5
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Re: Morgan NM 45 Hurth Transmission

Rob/beetle
Thanks...You have been a wealth of info.
I may pull the tranny before ordering a new one to see if it turns freely enough to determine the gear ratio. The Universal website says that they recommend a 2:1 gear ration and that max engine rpm is 2800 rpm.
That sure surprised me since I thought that the engines could easily handle max rpm of 3400 or so.
BTW,my two aluminum water tanks failed after only ten years of service(100
Gallons each) I hope you had better luck.
Aloha,
Len
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