 |
10-01-2023, 02:40 PM
|
#1
|
|
Senior Member
City: Beaufort, NC
Join Date: Apr 2019
Posts: 136
|
Cruise speed and fuel consumption
Good afternoon everybody. I’m eyeing a 78 29’ Prairie Trawler that’s fairly local to me. I love the small cozy layout. The seller said the 50 hp Perkins was recently rebuilt. What kind of cruising speed and fuel Milage do these pretty little trawlers get?
|
|
|
|
10-01-2023, 03:18 PM
|
#2
|
|
Guru
City: Guelph
Vessel Name: Escapade
Vessel Model: 50` US Navy Utility trawler conversion
Join Date: Nov 2015
Posts: 2,328
|
1/2 gph @ 5 knots
1 gph @ 6 knots
2 gph @ 7 knots
Or close to that.
|
|
|
|
|
10-01-2023, 03:30 PM
|
#3
|
|
Guru
City: West Coast
Join Date: Apr 2014
Posts: 1,786
|
That size makes 7 knots beyond displacement speed. I am skeptical that 50 hp is enough to push it faster than displacement speed.
|
|
|
|
|
10-01-2023, 04:19 PM
|
#4
|
|
Guru
City: Saint Petersburg
Vessel Name: Weebles
Vessel Model: 1970 Willard 36 Trawler
Join Date: Mar 2019
Posts: 6,722
|
Quote:
Originally Posted by Jeff F
1/2 gph @ 5 knots
1 gph @ 6 knots
2 gph @ 7 knots
Or close to that.
|
1/2 gph @ 5 knots
1 gph @ 6 knots
2 gph @ 6.7 knots
Better?
I owned a Willard 30 with a Perkins 4.108 50hp. I think Jeff F's numbers are pretty close. At displacement, a 29-footer will run 6 to 6-1/4 kts unless running WOT.
Peter
__________________
M/V Weebles
1970 Willard 36 Sedan Trawler
|
|
|
|
10-01-2023, 04:33 PM
|
#5
|
|
Guru
City: West Coast
Join Date: Apr 2014
Posts: 1,786
|
It was fine before. I was really just trying to say don't expect to cruise at 7 knots without pushing the engine to its limits, and even then it may not be possible.
|
|
|
|
|
10-01-2023, 05:07 PM
|
#6
|
|
Moderator Emeritus
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 20,565
|
Why would one expect that they will be able to run that boat more than hull speed? But below hull speed it should provide exceptional fuel economy.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you aren’t one, there is no explanation possible.
|
|
|
|
|
10-01-2023, 06:20 PM
|
#7
|
|
Guru
City: Seattle
Vessel Name: AZZURRA
Vessel Model: Ocean Alexander 54
Join Date: Aug 2017
Posts: 4,122
|
If you push the Perkins to 50hp you will burn 2.5 gallons an hour. As others have said your speed probably won’t reach 7kts.
|
|
|
|
|
10-01-2023, 07:49 PM
|
#8
|
|
Guru
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 27,700
|
If semi displacement and very close to the planing end of that design... why would 7 knots be so inconceivable at near full throttle?
The pics I have seen of a Prarie 29 hull look like they have pretty flat aft sections.
|
|
|
|
|
10-01-2023, 08:24 PM
|
#9
|
|
Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,720
|
Quote:
Originally Posted by mvweebles
1/2 gph @ 5 knots
1 gph @ 6 knots
2 gph @ 6.7 knots
Better?
I owned a Willard 30 with a Perkins 4.108 50hp. I think Jeff F's numbers are pretty close. At displacement, a 29-footer will run 6 to 6-1/4 kts unless running WOT.
Peter
|
Very close to my W30 experience.
__________________
Eric
North Western Washington State USA
|
|
|
|
|
10-01-2023, 08:41 PM
|
#10
|
|
Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,720
|
Quote:
Originally Posted by psneeld
If semi displacement and very close to the planing end of that design... why would 7 knots be so inconceivable at near full throttle?
The pics I have seen of a Prarie 29 hull look like they have pretty flat aft sections.
|
May have a lot to do w their beam.
But I’d guess the Prairie could be close to 10 tons.
Could be lower too.
I’m not even sure my W30 will reach 7 knots. Very close tho. But I was a bit shy of power at 37hp. And w the raked stem of the bow WLL is only 27.5’.
__________________
Eric
North Western Washington State USA
|
|
|
|
|
10-01-2023, 09:21 PM
|
#11
|
|
Guru
City: West Coast
Join Date: Apr 2014
Posts: 1,786
|
Quote:
Originally Posted by psneeld
If semi displacement and very close to the planing end of that design... why would 7 knots be so inconceivable at near full throttle?
The pics I have seen of a Prarie 29 hull look like they have pretty flat aft sections.
|
My intuition is that 50 hp (best case, engine may now make less) is not sufficient for that boat to get on plane. One of my first boats was underpowered but semi-displacement. If everything wasn't just right, it wouldn't be able to get on plane, but once it did, the engine could get a few extra knots. But, if the tanks were full, or I had too many people on board, or heading into wind, or chop, it would get stuck trying to get on plane (even though it was making full rpm.
|
|
|
|
|
10-02-2023, 01:00 AM
|
#12
|
|
Guru
City: League City, TX
Vessel Name: Pelago
Vessel Model: Wellcraft 3300 Coastal
Join Date: Aug 2011
Posts: 1,065
|
Quote:
Originally Posted by Nomad Willy
May have a lot to do w their beam.
But I’d guess the Prairie could be close to 10 tons.
Could be lower too.
I’m not even sure my W30 will reach 7 knots. Very close tho. But I was a bit shy of power at 37hp. And w the raked stem of the bow WLL is only 27.5’.
|
My previous Fales 30 Boomarang (Willard 30 clone) was powered by a fresh 56hp Yanmar with a well-tuned and matched 3-blade prop. Lightly loaded with a clean bottom it was capable of 7.2 knots. This was observed over a timed, 2-way measured nautical mile and was repeatable. The bow rise was dramatic, and wake pronounced. My normal cruise was ~6.75 knots. All of my dock mates had much faster powerboats and really resented me when I told them how much diesel I used. One used to joke that I stopped every month at the fuel docks to drain my excess fuel. He said my boat 'made gas'! 
__________________
Larry
M/V Pelago
|
|
|
|
|
10-02-2023, 10:19 AM
|
#13
|
|
Senior Member
City: Discovery Bay
Vessel Name: Cold Duck
Vessel Model: MS 350 Trawler, 1997
Join Date: Jul 2022
Posts: 295
|
Quote:
Originally Posted by mvweebles
1/2 gph @ 5 knots
1 gph @ 6 knots
2 gph @ 6.7 knots
Better?
I owned a Willard 30 with a Perkins 4.108 50hp. I think Jeff F's numbers are pretty close. At displacement, a 29-footer will run 6 to 6-1/4 kts unless running WOT.
Peter
|
5kts all day @ 1/2 gal/hr. Anything else is not reasonable. This was our Willard Vega ops @ 2200rpm. Anything more was really uncomfortable ride and noise wise.
|
|
|
|
|
10-02-2023, 11:06 AM
|
#14
|
|
Guru
City: Dewatto
Vessel Name: CHiTON
Vessel Model: Tung Hwa Clipper 30
Join Date: Jan 2020
Posts: 1,025
|
Tung Hwa 30. Similar hull with a Lehman 80 hp. Just finished a two month cruise of +700 miles, boat loaded to the gills, mostly at 6.4 knots. 1.4 gallons per hour including our tiny diesel heater. Top speed according to the Garmin was 11 knots, but that was current pushing in a passage. We tend to cruise between 1,600 and 1,800 (about 40 hp).
|
|
|
|
|
| Thread Tools |
Search this Thread |
|
|
|
| Display Modes |
 Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
|
» Trawler Discussions |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
