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Old 08-15-2014, 12:39 PM   #1
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How much HP?

I've had Prairie 29's on my short list for awhile now. I'd appreciate any comments on how much horsepower is needed to make sure a 29 can handle running against strong tides, currents, head winds and/or head seas. I've seen 29's with 50HP, 85HP and 100HP. What's needed in the real world?
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Old 08-15-2014, 01:05 PM   #2
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Let's see a good pic of the hull aft.
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Old 08-15-2014, 01:55 PM   #3
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Let's see a good pic of the hull aft.
Eric,

At one time, I was looking at the P29 too. Here are some pics. An interesting construction note is that Hargrave designed this boat with generous beam above the waterline, but kept the BWL as narrow as possible. Note the tapered/softer chine at the transom. I read this was to reduce wetted surface and make the boat more economical to operate. It also supposedly made rolling less harsh than if the beam had been carried all the way to the waterline with a hard chine.
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Old 08-15-2014, 02:47 PM   #4
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you don't need extra power to fight tides and currents because the boat will only go so fast through the water unless it planes. It does not matter how fast the water is moving. Waves and wind age are a different matter and extra HP helps a lot especially in bucking tall head seas that tend to stall the boat.
It is not the size of the engine that determines how much fuel you use but the speed you try to run. At 5 knots all engines will probably use similar fuel so I would go for the larger engine to have reserve power all things being equal which they never are.
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Old 08-15-2014, 04:49 PM   #5
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you don't need extra power to fight tides and currents because the boat will only go so fast through the water unless it planes. It does not matter how fast the water is moving. Waves and wind age are a different matter and extra HP helps a lot especially in bucking tall head seas that tend to stall the boat.
It is not the size of the engine that determines how much fuel you use but the speed you try to run. At 5 knots all engines will probably use similar fuel so I would go for the larger engine to have reserve power all things being equal which they never are.
Anyone have direct experience with a Prairie 29?
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Old 08-15-2014, 05:34 PM   #6
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TF Member FLAGOLD has extensive experience with Prairie 29. His name is Matt Mattson and has a lot of videos on youtube about cruising his boat.
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Old 08-15-2014, 08:25 PM   #7
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Boy does that bottom look like a Hatteras

Wonder why, by the size of that prop that boat isn't a powerhouse.
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Old 08-15-2014, 08:31 PM   #8
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No personal experience with Prairie 29s, but lots of experience with displacement hulls in that size and those HP engines. I am guessing that the 50 HP motor is probably a Perkins 4-108. It is called a 50 HP but it makes that at a high RPM that you would never run at. The 85HP would be a Perkins 4-236. Now you are talking! Lots of grunt at 1500-1800 RPM! It will push that boat as fast as it will ever go! This is the motor I would choose.
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Old 08-15-2014, 09:37 PM   #9
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I own a Prairie 29,SUE MARIE, with a Perkins 4-108,50HP. She has a left hand turning 18x12 driven thru a BW 2'9. Engine is listed at a 4000 rpm, real number is more like 3600. Sue Marie, cruises at 6.3+/_ at 2700 rpm. At 3000rpm she will reach 7. I have run one with the 4-236, an 85hp engine. The top there is 2800rpm. That would be my preference if I were building new.

I have no real complaints with the 4-108. She averages 1gal per hour and runs strong.

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Old 08-15-2014, 09:55 PM   #10
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Wonder why, by the size of that prop that boat isn't a powerhouse.
Didn't Hargrave design the older Hatteras motor yacht hulls?
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Old 08-15-2014, 10:06 PM   #11
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Thanks Larry for the pics.

All the engines mentioned would be appropriate .... probably.
This is at least a mid speed SD hull. But her wide beam may cause her to plow along bow high in the vicinity of "hump speed" making her hard to power intelligently. Running semi-slow (8 to 14 knots or so) is best done w a longer narrower boat.
But she would definitely benefit from more power than a similar length full displacement (FD) boat like my Willard .... that requires less than 35hp total and 18 for cruising.

35hp would be insufficient power for the Prairie. Fifty hp would be about right if one was not interested in top speeds over 7 knots. You may get 8 or 9 knots ......... I'm not sure ..with 85hp. Ask Prairie owners. But I would go w 50hp. And as mentioned the 107 and 108 cu in Perkins engines are only 36hp at 3000rpm. A 55hp Yanmar JH NA engine would be excellent as would be a 54hp Isuzu ... one of my favorites. An 80hp 4 cyl Lehman would also be an obvious candidate. Any good fifty to sixty hp engine should work out fine. You may come across a 75 or so hp Nissan engine. They were found in 27' Albins for one example. The Nissan is a 6cyl engine.

I think Al in Ketchikan has a Prarie. Contact him.
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Old 08-15-2014, 10:36 PM   #12
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If you look at the stern, the stern quarter and the entry you think you are looking at the old Hatteras 34
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Old 08-16-2014, 12:01 AM   #13
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Quote:
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Didn't Hargrave design the older Hatteras motor yacht hulls?
Yes he did. The Prairie 29 has sometimes been referred to as a 'Baby Hatteras' because of its lineage.

In the 70's I studied yacht design at Westlawn, and actually still have drawings I submitted that were graded by JBH, Jack B. Hargrave. He was on staff in those years, I think maybe as a volunteer to get Westlawn off the ground. He even liked one of my designs!


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Old 08-16-2014, 01:46 AM   #14
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Yes

Quote:
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Didn't Hargrave design the older Hatteras motor yacht hulls?
Yes and I think he new what he was doing.
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Old 08-16-2014, 10:35 AM   #15
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Sortie,
What does your Prairie weigh?

Larry M,
I was hot to go to Westlawn a long time ago, probably in the 60s. Was look'in at Embry Riddle fly boy school too.
In the middle picture in your post #3 notice the chine is not straight as many/most boats are. Generally speaking unless it's a planing hull straight lines fore and aft are undesirable. Sides and bottom included. Landlubbers mostly don't see the difference but Hargrave was no landlubber.
Something odd about that boat in the ctr pic is that it looks like the hole in the rudder dosn't even come close to lining up w the P shaft.
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Old 08-16-2014, 11:54 AM   #16
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Eric, 1300; you are correct, the hole in the rudder does not line up with the shaft. We had to drop the rudder to get the shaft out.

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Old 08-16-2014, 12:04 PM   #17
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These posts are very informative. I looked at some of Flagold's excellent videos.
I believe his boat had been repowered with a 6-cyl Yanmar. I assume that motor would be rated higher than 50HP.

Thank you for all these responses.
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Old 08-16-2014, 12:21 PM   #18
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I was under the impression that Mischief was repowered with Yanmar 55. The Perkins 85 gives you more power at a lesser rpm, top end slightly higher. This hull is going to cruise between 6-7 knts regardless of power. Too big of an engine could in fact be counter productive.

Check the postings on Miss Dot Dee. He saw a dramatic improvement in performance when he stripped his layers of bottom paint.

I am content with the performance of our boat. It is quiet, efficient and gives us all the speed we need for now. These vessels were not designed to be speed boats. .

I agree with Eric, I love the Isuzu engine. If I needed a new engine it would be my first choice, then the Yanmar 55. The Perkins 4236 is also a good engine.

Good Luck.
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Old 08-16-2014, 08:21 PM   #19
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I stand corrected on the repower on Flagold's Mischief:

". . . New Yanmar 4JHE installed 2008 - 436 hours."
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Old 08-16-2014, 10:28 PM   #20
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Eric- "Al in Ketchikan" here. We own a Marben 27 foot. Here is a copy of a sister advertisement. You can select the bottom to see that it is completely different from the Prairie. Al

1978 Marben Flybridge Trawler Pilothouse Pocket Cruiser Title
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