Author Topic: Propeller size help for the P323  (Read 1747 times)


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Propeller size help for the P323
« on: November 22, 2020, 06:53:02 AM »
Upon hauling out my 323 to remove and replace the oil pan I discovered my propeller and shaft need replacing. I'm confused about the prop sizing. On the parts list Pearson has it as a 15x8 but mine seems to be a 17 x12 LH. Does anybody know if besides being left hand or right hand they were sized differently for diesel or gas engines? Any insight appreciated as time is of the essence!
« Last Edit: November 22, 2020, 12:26:55 PM by admin »

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Re: Propeller size help
« Reply #1 on: November 22, 2020, 12:25:15 PM »
The engine size/type is the reason for the differences in prop sizes you found in the Pearson doc. The original owners manual lists the 17x12 prop for this boat.  The boat now has the Volvo D1-30 engine.

From the P323 Owners Guide:
> Universal Atomic 4, Model 5103-UJVD w/Aqua-Pak V-Drive, 2:1 Reduction 15x8 RH Style E, 1 1/8" bore

> Volvo MD 11C, 23HP Diesel 1.91:1 Reduction 17x12 LH Style E, 1 1/8" bore

Note: I documented sea trials in calm conditions in Nov 2019 when I owned this boat (Sea Fever) with the existing prop:
5.2 kn@1800 RPM
6 kn@2200 RPM
7 kn@2900 RPM

I am not experienced at sizing props but here are comments from forum users, if you have not already seen them:

Valor did a lot of prop research for the P323 equipped with a Yanmar 3GM30F, which is probably a good comparison to your engine.
My Yanmar 3GM30F has a max RPM of 3600. The boat was purchased with a 15x14 prop and I could only get 6kn@ 3300 RPM max which is why I was changing the prop. The new prop is sized at 15x9 which brings me to 3550 RPM. I normally cruise at 2800 RPM. My old prop with a fresh bottom was 5.5 knots @2800RPM. The new prop was 7.2 knots at 2800RPM. SOG was 6.8kn with a .3 current against. It really feels like a completely different boat when motoring now. When I upgraded to a PSS seal over the winter, I pulled the shaft, had it checked, cleaned and balanced just because. There is ZERO vibration of any type with the new prop as well.

Rbrtfeld put a folding prop on his P323
I believe the Maxx prop was a 15 inch LH prop. They then told me what setting I needed when I put the prop together on the boat. There is a good video on YouTube for maxx prop. I have the original 17inch LH brass prop that was on the boat if anyone needs one.

« Last Edit: November 22, 2020, 04:10:07 PM by admin »
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Re: Propeller size help for the P323
« Reply #2 on: November 23, 2020, 12:28:15 AM »
I also put a max-prop on Selene. 3-blade, 15x9. Love it.

The boat came with a fixed prop: LH, 3 bladed, marked 13 x 9 1/2 on 1.125" shaft - but when researching, I was told that 15 x 8 was the standard sizing.

In the forums we had much discussion a few years ago about RH vs LH. Note that the shaft offset was defined by the engine (Petrol or diesel), which apparently rotate the prop in different directions - so some people found propwalk issues if they repowered with different engine.

I would be cautious about going much bigger than 15". You need clearance between the blades and the hull - not because of the risk of an impact, but because, if the blades are too close to the hull, apparently it creates interference/turbulence which reduces the efficiency of the prop. Research it yourself and decide what works for you - I am no expert!

FYI, my RPM/Speed results are as follows (Westerbeke 30B3, 27hp, flat water):
2000   5.2kn
2200   5.8kn
2400   6.2kn
2600   6.5kn