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Old 17-05-2012, 14:17   #1
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reduction gear for HR 42

I am purchasing a Hallberg-Rassy 42 with a 76 HP volvo engine, it has a 20” max prop but on the sea trial I wasn’t able to drive the engine up to full rpm or gain full hull speed. I guess it could be the pitch of the max prop because in neutral the engine went to full rpm. (Ideas here?)

I talked to the PYI for a recommended pitch setting for the 20” max prop but I can’t find any information on this through a google search… any suggestions?

Thanks ahead of time.
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Old 17-05-2012, 14:34   #2
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Re: reduction gear for HR 42

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Originally Posted by darkaegisagain View Post
I guess it could be the pitch of the max prop because in neutral the engine went to full rpm. (Ideas here?)
It could be the prop, but another possibility is that engine is unable to develop full power for some other reason, like, for example, fuel delivery problems (clogged filters and such).

One suggestion is to find another owner of HR 42 with identical config and ask if they get full rpm under load.

Just a thought.
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Old 17-05-2012, 14:44   #3
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Re: reduction gear for HR 42

how foul was the hull and prop?
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Old 17-05-2012, 14:48   #4
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Re: reduction gear for HR 42

Go to Max Prop website and you should find their charts along with You Tube instructions on how to set prop.
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Old 17-05-2012, 14:49   #5
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Re: reduction gear for HR 42

You will need to determine if your prop is right and or left hand
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Old 17-05-2012, 14:57   #6
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Re: reduction gear for HR 42

Had this problem on a HR 43 last year, the "previous guy" set it up and all appeared to be correct. The original prop was hanging in the engine compt. I noticed it was LEFT handed, dived under the boat and saw that the J-prop (similar to Max) was set up for RH and it was pitched really steep. Black smoke etc...so I changed the pitch (Scuba gear and a weighted bucket for the tools) so it looked like the original prop, plus a few degrees because there is no rake on a J-Prop. Problem solved.
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Old 17-05-2012, 15:26   #7
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Re: reduction gear for HR 42

The bottom is clean enough, maybe another year before we paint it. But it may be the LEFT hand issue described above? I know compared to my current boat the HR walks the other way in reverse compared to a Yanmar so its definitely a possibility. The other is that the prop may be just too big at 20”…
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Old 17-05-2012, 16:56   #8
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Re: reduction gear for HR 42

Go to your boat's owner's manuel or an HR owners website and determine what size and pitch prop you need. We already know you have a 20" prop. Go to the Max-Prop Propeller website and click on the owners manuel for your specific 20" prop. Then cross reference to the recommended pitch and you will have the recommended settings for your boat and prop. They make several types of adjusting props. There will be a chart which will tell you the correct settings for the correct pitch for your 20" prop. I pitched mine one more inch than what Max-Prop recommends because the boat was over reving at full throtel. Your prop may be over pitched (most likely) or pitcehed for the wrong rotation of the prop (less likely).
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Old 19-05-2012, 09:45   #9
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Re: reduction gear for HR 42

With some help from Volvo for the reduction ratio and PYI we determined that the 20" prop was too big. Since PYI is local they are going to cut the prop down to a 18" and set the pitch correctly for the boat.
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