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Old 01-02-2016, 11:43 PM   #141
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Eric, ran it through the formula with 12 foot beam, same result-Your point?

Yes our boat is 10 foot again, your point?
It is documented within the conversations (Post) to the thread that our boat is 10 feet at the wide point and tapers to 9 feet across the stern. Where as I believe there is comment that the prairie carries out straight beam to the stern.
11 feet or 12, apparently for the purpose of wheels in this case the end result is confirmed. Too, I used the 16 knot as a factor one time and the 7.2 knots as a second factor and the wheel measurements did not alter. I found that a bit strange,yet it makes sense. The wheel should be for the opium and what setting the operator chooses below the max is their choice.

One should be pleased at to days prices for wheels, to find that the wheel being used confirmed correct or near so,by a second qualified opinion (Vic Prop) I did use a 2:l gear ratio which was not given by the poster.

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Old 01-03-2016, 06:44 PM   #142
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Does your prairie still have the engraved plaque with RPM and MPH listed mounted on upper console? ( at least that's where mine is). The max speed listed on mine is 9 MPH. That's 7.8 knots. Sorry. These fine vessels don't do more than that. If they did the Manufacturer would have 'made it so number one.' Not sure where you want to go with Willow B. But over 8 most likely ain't gonna happen no matter what you do to prop, engine HP or rpm.

I'm going to check up on boat Sunday. I'll try to take a pic of the plaque.

It's funny you mention the original bill of sale. I have that also. $118,000 for this little girl!

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Old 01-03-2016, 08:16 PM   #143
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Does your prairie still have the engraved plaque with RPM and MPH listed mounted on upper console? ( at least that's where mine is). The max speed listed on mine is 9 MPH. That's 7.8 knots. Sorry. These fine vessels don't do more than that. If they did the Manufacturer would have 'made it so number one.' Not sure where you want to go with Willow B. But over 8 most likely ain't gonna happen no matter what you do to prop, engine HP or rpm.

I'm going to check up on boat Sunday. I'll try to take a pic of the plaque.

It's funny you mention the original bill of sale. I have that also. $118,000 for this little girl!


Maybe if you installed a 200 HP Volvo.
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Old 01-03-2016, 09:25 PM   #144
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Al wrote;
"Eric, ran it through the formula with 12 foot beam, same result-Your point?"
"Yes our boat is 10 foot again, your point?"

I was trying to show that the Prairie is a considerably larger boat being 2' wider. Should be a significant difference in weight. And weight is directly proportional to the amount of power required to push the hull. Beam gets into the picture but displacement is far more demanding of power. I once thought of a W-30 w a 12' beam. Don't think I'd need a bigger engine to drive her at the same speed as the 10.5' hull. HP per ton of displacement is a common way of contemplating power required.

Anyway I was just drawing attention to the fact that the Marben and Prairie are different sized boats .. one probably needing more power than the other.
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Old 01-03-2016, 10:44 PM   #145
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TE=manyboats;401104]

Quote:
Anyway I was just drawing attention to the fact that the Marben and Prairie are different sized boats .. one probably needing more power than the other.[/QUOTE]


Yes, for sure, in this case, the larger boat Willow-B (Prairie) has the smaller 4-108 (38 HP)engine 3000 RPM rated. We had the 4-154 (58 HP) that engine is a 3000RPM rated and now the even larger 4-154 (85 HP) rated at 2800 RPM. All in all I think that among these posting Prairies there is a full selection of engines. 108/236/125 (HP) all Perkins and the 200 HP Volvo. In the end the hull speed remains the same for all the boats. How you get to hull speed or exceed it is owner driven.
Good thread. enjoyed the conversation and learned a good amount of information on the Prairie.
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Old 01-04-2016, 07:31 AM   #146
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Prairie 29 engines

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Maybe if you installed a 200 HP Volvo.

I have an aversion to paying more for a new engine than I paid for the entire boat! And I do like to be able to speak and have a comfortable salon (decibel wise) when out running.

My 4.236 is pressed right up to the floor boards as it is. I don't have measurements of the Volvo, but generally the larger the HP, physically the larger the whole kit and caboodle is Its 'just' possible to get around the engine now. I can't imagine having less space to do ordinary maintenance with a larger engine.

Besides...... I'm happy doing 6 to 7. Life is too short for being happy only at XX kts.
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Old 01-04-2016, 08:21 AM   #147
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The 4-236 is a big engine. Bigger than most later model 200 hp units. Its a great engine, but small,smooth and quiet it is not.
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Old 01-04-2016, 08:35 AM   #148
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[QUOTE=cappy208;401174]I have an aversion to paying more for a new engine than I paid for the entire boat! And I do like to be able to speak and have a comfortable salon (decibel wise) when out running.

If there is a bright side to having an engine that's something like four times too large, it's that I can cruise at seven-point-something knots at 1200 rpm, which makes the noise level very low indeed.

...that and it eliminates the need to add ballast.

There's always a bright side somewhere.

Cheers!

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Old 01-04-2016, 10:51 AM   #149
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Heron- Given access to several posters with this boat, I would think your boat comes in nearer 11,000#. The Prairie is so close to our Marben in style, displacement and such. Out of the box the Marben weighs 10,000#

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Just for the heck of it I ran your info through Vic prop to see how close. I did use 12000# as the weight.
According to the results, a 2 blade wheel would be 21X13.2
3 blade would be 20,3X13.1
and a 4 blade is 19.1x12.8

Using one inch in diameter equals 2 inches of pitch it would seem you have hit the bulls eye as the adjustment for that formula would have you with a 18X14.8 or rounded off 18X15. Pretty darn close which gives a bit of credence to the formula.
It has for me over the times used.

Al-Ketchikan
Our out of the box spec is 8500 lbs. add Fuel and water. The big Volvo may add to that....Being small we don't have a lot of "Stuff", but you're right...Maybe more than 9500lbs.
10 beam, SD hull. The Volvo WOT rating is 3600 and that's exactly what she'll do with a clean bottom. I'm guessing I'm propped pretty much perfectly. The previous owner took it from 18x16 to 18x17 to fine tune it some years ago and I don't see any reason to change that.. Seems we're all different here...
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Old 01-04-2016, 03:43 PM   #150
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The 4-236 is a big engine. Bigger than most later model 200 hp units. Its a great engine, but small,smooth and quiet it is not.
As one who ran the Perkins 4-154 (58HP) for several years, one of the considerations and proven true in our case, is running the larger 4-236 at 1400 RPM vs. 2400 RPM of he 154 in the same engine area is one Heck of a lot quieter, and it the 4-236 is just as smooth as the 154, which too is a smooth running engine. Yes, it could be said that the physical size might equal a larger rated HP modern engine. The off set is that the newer lighter engine will be turbocharged in most cases which by the design require a high RPM range to address the needs of a turbo application. There again, is the higher sound factor.
Two different category of engine and times. I can recall in my early years on the commercial saine boats where captains would argue over the 'Stamp mill" old Atlas, Fairbanks-Morse, Enterprise,and Washington being the older engines vs. what was then the 'New" boys on the block, 671 Jimmy, Volvo(coming to America around the 50's) Perkins Caterpillar and such, non except for the 2 cycle, turbocharged, and now they are the 'Old"men of the current conversation. The discussion then is as it is now. Not too much change and still an interesting ongoing subject.
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Old 01-04-2016, 04:35 PM   #151
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Al,
I worked at Washington Iron Works. They had long since stopped making the Washington Diesel engine but I went through a lot of old drawings of the engines. Three cyl to 10 cyls were there. All made there on 4th ave so in Seattle. That was in 1959 .. just before I went to work in the gold mines in western Alaska near Bethel.
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Old 01-04-2016, 05:10 PM   #152
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And 0' Golly! The sounds of those stamp mills in the fleet of halibut schooners that traversed the channel coming one after another in a solid continued line like a string of snow geese before the season started,into Ketchikan A young boy would listen to the "Pukka, pukka, pukatchuck, each engine made and at a different cadence according to those number of cylinders employed. Good days and good sounds. There are a couple of the old schooners (Tugs too) still powered suchlike . You were fortunate to have worked and I suspect too had listened to the solid "Curchuncks"
Here you go:

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Old 01-08-2016, 09:40 PM   #153
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We launched Sue Marie today. She had been on the hard for a month, removed all the bottom paint, put back four coats of barrier protection two coats of petit Bottom paint. Also switched props. Had a 18/12/3 blade prop, replaced with a 18/13/4 blade.

Had a smooth but rainy day for our 17 mile ride back to our home port. an smooth, and quiet. Too her up to 2600 , louder , reached 6.8 . Put prop speed on the prop, used this product in the past on a twin engine sport fisherman. In these warm waters it works great.

Wanted to do this project three years ago, with my wife's illness had no time. Glad I got it done.

John
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Old 01-08-2016, 11:10 PM   #154
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[QUOTE=Sortie;402664]We launched Sue Marie today. She had been on the hard for a month, removed all the bottom paint, put back four coats of barrier protection two coats of petit Bottom paint. Also switched props. Had a 18/12/3 blade prop, replaced with a 18/13/4 blade.

Had a smooth but rainy day for our 17 mile ride back to our home port. an smooth, and quiet. Too her up to 2600 , louder , reached 6.8 . Put prop speed on the prop, used this product in the past on a twin engine sport fisherman. In these warm waters it works great.

Wanted to do this project three years ago, with my wife's illness had no time. Glad I got it done.


So in the end, you did go for the bigger wheel. You indicate 2600 RPM.What now during a short effort, is your WOT? I recall you mentioning 4000 RPM by engine data was WOT, then again, I want to recall without reviewing the thread, that contrary, your top WOT was less. That being with the smaller wheel. Within prior conversations shared by Manyboats (Eric) addressing the need to reach engine manufactures RPM as wheel selections are anticipated, it would appear that you have made a satisfying choice on the wheel. Eric is correct in his prognostications and the unknowing or inexperienced should heed the manufactures recommendations. Some challenge in the spirit of 'Tweaking' the recommendations to optimize a specific desired outcome.
Glad to hear that your effort on 'Tweaking' paid off.
By the way, had you ever had or know of the 4-108 having habituial rear main seal leaking??
Thanks and to the thread and Prairie owners. I count this thread with the amount of good sharing of different points of view as one of the better sites. As the Prairie is close in all sectors with our Marben.

I'd ask to be adopted into the Prairie owners category as our craft source of information and ownership's is skimpy. This category serves as a friendly bunch and source. to bounce off similar subject matter.
Cheers

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Old 01-08-2016, 11:19 PM   #155
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Al,
He did say he put on the 4blade. But he didn't say 2600 was WOT.
I don't know for sure but I'd be inclined to consider the 107/108 Perkins a 3000rpm engine. Every engine I've known is 3000 but I've read about the English taxi cabs w 50hp at 4000rpm. The 3600 and 4000 engine rating is a bit of a mystery to me.
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Old 01-09-2016, 12:51 AM   #156
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Al,
He did say he put on the 4blade. But he didn't say 2600 was WOT.
I don't know for sure but I'd be inclined to consider the 107/108 Perkins a 3000rpm engine. Every engine I've known is 3000 but I've read about the English taxi cabs w 50hp at 4000rpm. The 3600 and 4000 engine rating is a bit of a mystery to me.
Eric,



Those are "marine ratings" and they come straight from Perkins:
  • 3000 rpm is "Max. continuous rated speed"
  • 3600 rpm is "Max. intermittent speed"
  • 4000 rpm is "Max. speed for approved high speed pleasure craft"
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Old 01-09-2016, 01:11 AM   #157
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Hi Eric,

Quot:[QUOTE=manyboats;402698]Al,
He did say he put on the 4blade.

Correct Eric, but the poster indicated a four blade dia and pitch 18X13 indicating that the wheel is larger than the three blade 18X12 he had before.

Normal formula results have a four blade measurements less than the three blade. Here by the numbers given, he has increased the wheel sizing hence the WOT now becomes interesting to see if he is 'right on' or over wheeled.

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Old 01-09-2016, 01:32 AM   #158
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Eric,



Those are "marine ratings" and they come straight from Perkins:
  • 3000 rpm is "Max. continuous rated speed"
  • 3600 rpm is "Max. intermittent speed"
  • 4000 rpm is "Max. speed for approved high speed pleasure craft"
Eric, here is a good point to throw around. Our 4-236 corresponding information as I recall was 2500 RPM for Continuous rated speed, 2800 RPM for intermittent speed. When we were cussing and discussion wheel choices during the re-fit the final decision was go with the 2500 RPM rating. We did and of course the results were as reported, we were only able to obtain 2000 RPM WOT. So as you and I have discussed, I am horrendously over wheeled.
Enough to make a knowledgeable prop person to cringe for sure. Actual running has proved that there is no advantage of running the engine more than 1450 RPM to obtain the hull speed which is graceful and pleasant to the soul. Still as stated often, we still have 500 RPM to WOT. And by diesel talk, 3/4 of engine throttle usually equates the best torque range.

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Old 01-09-2016, 07:06 AM   #159
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WOT on my boat is now and has always been 3600. According to the original owners notes, he never achieved anything over 3600,nor he really try. I have had the same experience. After 3100 rpm, the engine does not sound happy. The owners Manuel repeats the Perkins numbers for the 4-108.

Al, the 4-154 was known for rear main issues. My goal is to have an efficient and smooth a ride as possible. If I can achieve hull speed at 2500 I am happy.

John

Al, you are a member of the Prairie group.
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Old 01-09-2016, 10:34 PM   #160
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Sortie- Thanks and I will attempt to live up to the extended honor!

Your response to me indicates that WOT is short. Not by much when you consider 3100 vs. 3600. One question. You indicated 'Rough sounding and not happy'. Is that 3100 WOT or is there more throttle and you are reluctant to push it? Second, Eric should consider your information and allow it to align it self with his calculations. It would seem you will not be hurt in either discussion.
Thanks on the confirmation of 4-154 seal issues. I had asked as I had not heard any on either the 107/108 although to my understanding the rear seal assembly is similar or same. I did suggest to the party that purchased our 4-154 to have the rear seal, recently replaced, done again as the recent fix was showing signs of leaking.
We took a 9 hour voyage today. Ran at 1450 and maintained a 6.9 knot average. So quite, we spoke in normal voice. Apple pie and ice cream didn't hurt either!!!
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