Author Topic: Pearson 323 boat speed under power?  (Read 1602 times)

Stuart Farrell

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Pearson 323 boat speed under power?
« on: October 07, 2022, 12:02:10 AM »
I was wondering if I could get some input regarding boat speed under power at your cruising rpm.

I recently changed engines on my Pearson 323 and added a feathering  propeller, and the pitch of the new prop is was off, I am under pitched as at cruising rpm I am at 5.5 knots, and if there's wind and waves I am at only 4.5!!!!!

Before the engine change, I was at about 6 to 6.2 knots at cruising rpm. How does that compare with everyone else?

Thanks for any input, cheers!

Stuart Farrell
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Dolce_Vita

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Re: Pearson 323 boat speed under power?
« Reply #1 on: October 11, 2022, 10:05:01 AM »
Our 1977 P323 is driven by a 25HP Atomic 4 gas engine, and has a 3-blade 15R8 prop driven thru a 2:1 V-drive.  In calm water with a clean bottom, we can get it up to just over 6 kts @ 3100 RPM.
@(^.^)@  Ed
1977 P-323 #42 "Dolce Vita"
with rebuilt Atomic-4

Stuart Farrell

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Re: Pearson 323 boat speed under power?
« Reply #2 on: February 08, 2023, 10:55:15 PM »
Thanks for the info Ed!

What types of speeds do you get when battling 20-25 knot winds? Does your speed drop of dramatically?

I have a 30 hp Yanmar, with a 3 bladed prop, so I know I should be able to go faster. It's just confusing trying to get the correct pitch on the prop and at the same time avoid being over pitched!!

Stuart

Last Resort

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Re: Pearson 323 boat speed under power?
« Reply #3 on: February 10, 2023, 04:00:07 PM »
you should've got suggestions for a new prop/pitch/diameter from the engine seller.  Also, the rpms are important for full speed.  With my 2gm20, a 16D 11P would only give me 2600 rpm at full throttle and I'd achieve 6kts, but I could not beat against any strong waves without dropping to well below 3kts speed. I went to a 15D 11P prop and now gained 800 rpms, and now can achieve over 5kts against strong waves no problem. So all that said, how many rpms are you getting now with the new motor. If you're reaching above 3000rpm and no speed, my guess is your under propped, and of course if the opposite and can't get more than 2500rpm, then over propped.  Either way you need to work with both the diameter and pitch of the prop to get the best results.  I haven't looked into it yet, but like you, if I installed a new motor, I'd go 25/30hp as well, but just off the top of my head, I presumed I'd have to go with a bigger diameter than 15" and find the appropriate pitch to match, and expect the engine seller to provide the info for his prop in my boat. Good Luck!!!

Dolce_Vita

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Re: Pearson 323 boat speed under power?
« Reply #4 on: February 13, 2023, 12:35:26 AM »
Thanks for the info Ed!

What types of speeds do you get when battling 20-25 knot winds? Does your speed drop of dramatically?

It depends strongly on the sea state. I once powered thru a 35 kt gale on the Chesapeake. As long as I kept to a windward shore I could manage 2-3 kts, but as soon as passed an open spot with lots of fetch, speed would drop to zero with each wave. Average was about 1kt.  It was most unpleasant.
@(^.^)@  Ed
1977 P-323 #42 "Dolce Vita"
with rebuilt Atomic-4