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Old 12-06-2016, 09:42   #1
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LOWER HORSE POWER

We have a Hunter Legend 37, 14,900# light ship, probably 17,000+ as is. Just blew the original Yanmar 3HM35F diesel (34 HP), have available a 30 HP Yanmar as replacement. I believe our prop is 16" x 10, two blade.

Anyone have experience or wisdom on a repower like this? Or are driving a boat of similar displacement with 30 HP?

Many thanks, Don
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Old 12-06-2016, 09:55   #2
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Re: LOWER HORSE POWER

Maybe compare the HP curves on the two engines. Some engines are rated HP at very high rpm, which really means it's not that HP to me......others not so much.... Depending on that it may work fine. My Hans Christian 38, a very heavy boat, had a 25 HP Yanmar in it. It was not enough really in a chop etc, but was in there for many years. It was an older Yanmar rated at a lower rpm though.
Which model is the 30 Hp yanmar you are considering?
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Old 12-06-2016, 12:03   #3
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Re: LOWER HORSE POWER

There's a 3HM35F on Ebay in Connecticut w/300 hours for $2000. No big alignment change, fuel, power, etc.

Yanmar Diesel Engine 3HM35F Used | eBay
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Old 13-06-2016, 01:59   #4
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Re: LOWER HORSE POWER

How did the boat handle with the 34hp? Assuming it was plenty, you can probably get away with the small decrease in power to 30hp. If the 34hp was marginal, I wouldn't do it.


If you do it, set aside a little bit to have the option to change out the prop, if it can't get up to full RPM with the lower HP, a drop in the pitch to 8" or 9" will probably get you back the full RPM.
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Old 13-06-2016, 04:53   #5
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Re: LOWER HORSE POWER

My portly Allied Seawind II weighs in more than 15,000 lbs and originally had a 25 horse W30. I have since replaced it with a Beta 30 which does fine, 16" prop as well.


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Old 13-06-2016, 10:16   #6
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Re: LOWER HORSE POWER

Quote:
Originally Posted by valhalla360 View Post
...set aside a little bit to have the option to change out the prop...
No need to change it; just re-pitch.
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Old 13-06-2016, 10:54   #7
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Re: LOWER HORSE POWER

Quote:
Originally Posted by stevec195 View Post
My portly Allied Seawind II weighs in more than 15,000 lbs and originally had a 25 horse W30. I have since replaced it with a Beta 30 which does fine, 16" prop as well.


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Our also chunky allied seawind II with a Phasor 30 does quite well also (14,900 light, best guess now would be 16,000). With a 16"x10" prop we generally cruise at 1800-2200 rpm (max of 3000) and make 4.5-6 through the water depending on conditions. There is plenty of extra power beyond that.


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Old 13-06-2016, 11:22   #8
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Re: LOWER HORSE POWER

Thanks to all who have replied, this forum is indeed a great resource!

Don
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Old 13-06-2016, 12:28   #9
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Re: LOWER HORSE POWER

I repowered my CL35 with a 27 hp 3YM30 when I replaced a 40 hp Pathfinder. It would be about the same displacement as your boat and I find it has worked well. I did talk to Bob Perry before making the change and he was confident it would do the job.
Good luck with the changeover!
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Old 13-06-2016, 15:36   #10
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Re: LOWER HORSE POWER

Thanks, we'll go with the 30 HP Yanmar and report how it does. If the mechanic will certify it will turn up to rating & compression proves good.

Thanks again, Don
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