Best Prop for 1994 Oceanis 351

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Allen Dick

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May 21, 2021, 2:21:36 PM5/21/21
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My 1994 Oceanis 351 with a Perkins 103-10 engine has had a Max-prop
since I bought the boat.

The manual says the engine is rated at 28 HP at3,600 RPM so 2800 seems
like a reasonable cruise speed but 2600 sounds best.

I am finding that I am lucky to make more than five knots at 2,600 RPM
and it seems to me that I should be making at least six knot at that RPM.

A three-blade prop that came with the boat as a spare  is in the hold
and I assume it could be the original.  I could have the diver change it
but that costs and could be a mistake.

What props are people using on similar boats and what sort of cruising
speeds are they seeing?

Andrew Kevin Callahan

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May 21, 2021, 2:56:06 PM5/21/21
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36 cc with a 30GM  hp Yanmar – original 3 blade fixed prop on since I bought the boat 21 years ago. Usually cruise at 2600 (max RPM reported as 3200). With a clean bottom and keel  will do about 6.4, later on in the season I’m lucky to get 5.6 to 5.8.

 

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Uwe Mewes

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May 21, 2021, 3:44:08 PM5/21/21
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Please see below. Do the calculation for your boat and you have a great starting point.

As a very general rule the maximum speed of any displacement hull--commonly called its hull speed--is governed by a simple formulahull speed in knots equals 1.34 times the square root of the waterline length in feet (HS = 1.34 x √LWL)

          Good Luck

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mechone

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May 21, 2021, 11:05:03 PM5/21/21
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I have same boat ,same engine ,hurth hbw100 trans  and a kiwi prop and make 7knots at 2800

allendick

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May 22, 2021, 8:59:41 AM5/22/21
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Thanks for the useful comments.  I should have mentioned the transmission is an HBW 100 2.5

I know that I am not up against hull speed by the fact that the boat sails faster than it motors so I have been beginning to think that this Max prop either needs adjustment or replacement.  Seeing as I have a spare and it is likely the original, I may just have the diver switch props.  He is unwilling to adjust this older Max-prop for fear of losing pieces into the soft mud bottom here in the marina.  Of course if the Max-prop is taken off, it can be adjusted in case we decide to re-install it.

Brian W

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May 22, 2021, 10:30:05 AM5/22/21
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We had a fixed prop on our new to us First 405. During the sea trial the engine was able to rev significantly above max rpm. We got a MaxProp and love it - lower fuel consumption, better speed and great going into reverse if you delay slightly in changing from forward to reverse. The setting was recommended by the folks we got it from (PYI). If you still need the correct settings they may be able to help (need engine and transmission model numbers). Make sure whatever the settings, your engine stays within the recommended RPM limit.
Brian
s/v Toujours

On Sat, May 22, 2021 at 8:59 AM allendick <alle...@gmail.com> wrote:
Thanks for the useful comments.  I should have mentioned the transmission is an HBW 100 2.5

I know that I am not up against hull speed by the fact that the boat sails faster than it motors so I have been beginning to think that this Max prop either needs adjustment or replacement.  Seeing as I have a spare and it is likely the original, I may just have the diver switch props.  He is unwilling to adjust this older Max-prop for fear of losing pieces into the soft mud bottom here in the marina.  Of course if the Max-prop is taken off, it can be adjusted in case we decide to re-install it.

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John Pool

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May 23, 2021, 3:09:35 AM5/23/21
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I get 7.5 knots at 1800 rpm

Sent from my iPhone

On 22 May 2021, at 13:05, mechone <saili...@gmail.com> wrote:

I have same boat ,same engine ,hurth hbw100 trans  and a kiwi prop and make 7knots at 2800

Allen Dick

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May 23, 2021, 8:58:44 AM5/23/21
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> I have same boat ,same engine ,hurth hbw100 trans  and a kiwi prop and make 7knots at 2800

That strikes me as reasonable. I'd be interested in what the RPMs are at WOT.

> I get 7.5 knots at 1800 rpm

On the other hand this seems odd to me if it is the same boat, same moto, and same transmission.

Even sailing without engine under ideal conditions 7.5 knots is pretty fast for this boat, and 1800 is far down the power curve so this result is surprising.  

I'd be interested in more details. 




Johnny Pool

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May 23, 2021, 7:02:48 PM5/23/21
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I have Bene 42s7 first ,Volvo MD22 driving a hydralign three blade feathering prop ,7.5 knots at 1800 rpm ,rarely exceed 2000rpm only when I want to load the engine ,even so only increase by 2 knots .Hull speed is somewhere around 8 k 

Johnny Pool

On 23 May 2021, at 22:58, Allen Dick <alle...@gmail.com> wrote:


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mechone

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May 23, 2021, 7:16:46 PM5/23/21
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Me too , the pitch is adjustable but not that much , quite frankly that would be very hard on the engine  .The engine would stall going into reverse as the kiwi gives you full pitch in reverse.I can only hit 3000 rpm WOT and maybe hit 7.2 on a good day. If engine is running that slow it would destroy the engine , the M30 like all diesels should run at about 80 % of max Rpm which is 2880 

John Pool

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May 23, 2021, 9:12:55 PM5/23/21
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I had a kiwi prop on my previous yacht Bene 38s5 first ,ran out of revs astern as correctly stated prop goes to full pitch astern 
Nothing wrong with pitch settings it was the turbo elbow choked up if you have a low hp motor boosted with turbo you can or will loose up to 40% output if the elbow is choked with carbon more than 50%
I now go with naturally aspirated engines so you don’t need to rev the guts out of it to achieve HP at 2800 
I have 9800 hours on my engine at 1800-2000 rpm good as new it’s about torque and load which is where correct prop pitch comes in 

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On 24 May 2021, at 09:16, mechone <saili...@gmail.com> wrote:

Me too , the pitch is adjustable but not that much , quite frankly that would be very hard on the engine  .The engine would stall going into reverse as the kiwi gives you full pitch in reverse.I can only hit 3000 rpm WOT and maybe hit 7.2 on a good day. If engine is running that slow it would destroy the engine , the M30 like all diesels should run at about 80 % of max Rpm which is 2880 
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