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08-06-2020, 09:25 PM
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#2
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Guru
City: Los Angeles
Join Date: Feb 2020
Posts: 1,487
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Quote:
Originally Posted by Swfla
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Sure, does it seem too slow?
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08-06-2020, 09:42 PM
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#3
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Moderator Emeritus
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 21,131
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It seems a bit fast to me. But also it says MPH not Knots. So 10 mph is a bit over 8.5 knots which is about right with 120s.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you aren’t one, there is no explanation possible.
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08-06-2020, 09:49 PM
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#4
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Senior Member
City: San Diego
Join Date: Jul 2020
Posts: 478
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I too thought it a bit fast. My limited knowledge of trawlers based on reading posts on this forum and looking at listings seems to me 8.5 would be it's top speed. Hoping some GB 42 owners would post here as well. Both of your posts are appreciated. Thanks.
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08-06-2020, 10:00 PM
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#5
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Moderator Emeritus
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 21,131
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I think that they could go faster than 8.5 knots but you would be pushing the engines more than I would like.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you aren’t one, there is no explanation possible.
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08-06-2020, 10:42 PM
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#6
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TF Site Team/Forum Founder
City: League City, Tx
Vessel Name: Floatsome & Jetsome
Vessel Model: Meridian 411
Join Date: Oct 2007
Posts: 7,332
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WFO.....yes.....but realistically that is an 8 knot boat(9.5mph)
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Prairie 29...Perkins 4236...Sold
Mainship Pilot 30...Yanmar 4LHA-STP...Sold
Carver 356...T-Cummins 330B...Sold
Meridian 411...T-Cummins 450C
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08-06-2020, 10:59 PM
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#7
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Guru
City: Qualicum Beach, Vancouver Island
Vessel Name: Capricorn
Vessel Model: Mariner 30 - Sedan Cruiser 1969
Join Date: Feb 2019
Posts: 2,019
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Maximum displacement speed is square root of water line times 1.34. So I assumed water line to be 38 feet and square rooted that and multiplied by the factor to get 8.3 knots.
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08-06-2020, 11:46 PM
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#8
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Guru
City: Seattle
Vessel Name: AZZURRA
Vessel Model: Ocean Alexander 54
Join Date: Aug 2017
Posts: 4,281
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No people, no gear, no water, very low fuel and throttle wide open on a dead calm day. Then just maybe you will see 13 MPH. Reality, it’s an 8 knot boat.
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08-07-2020, 05:21 AM
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#9
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Guru
City: Aventura FL
Vessel Name: Kinja
Vessel Model: American Tug 34 #116 2008
Join Date: Oct 2017
Posts: 10,595
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Quote:
Originally Posted by tiltrider1
No people, no gear, no water, very low fuel and throttle wide open on a dead calm day. Then just maybe you will see 13 MPH. Reality, it’s an 8 knot boat.
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__________________
Two days out the hospital after a week in the hospital because of a significant heart attack.
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08-07-2020, 08:37 AM
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#10
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Senior Member
City: San Diego
Join Date: Jul 2020
Posts: 478
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Thanks to you all. So many on this forum talk about running at 6-8 knots. The ones who run normally at 6 are just babying their gear and/or watching gph flow.
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08-07-2020, 08:57 AM
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#11
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Senior Member
City: Boston
Vessel Name: Rose Mary
Vessel Model: 42 Grand Banks Motoryacht - 1985
Join Date: Feb 2017
Posts: 271
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Quote:
Originally Posted by tiltrider1
No people, no gear, no water, very low fuel and throttle wide open on a dead calm day. Then just maybe you will see 13 MPH. Reality, it’s an 8 knot boat.
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Agreed.
We have a GB 42 with twin Lehman 135s. We cruise between 8.3 and 8.5 knots (10 MPH) at 1800 RPM regardless of weight. It's very comfortable there. We push it every once in a while to 2400 to stretch the legs, at which point we go 10.5 knots (12MPH). 2600 is max loaded RPM for our engines.
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08-07-2020, 09:05 AM
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#12
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Guru
City: Southport, FL near Panama City
Vessel Name: FROLIC
Vessel Model: Mainship 30 Pilot II since 2015. GB-42 1986-2015. Former Unlimited Tonnage Master
Join Date: Oct 2007
Posts: 4,977
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Quote:
Originally Posted by Swfla
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My twin Lehman 120s in my own 1972 Grand Banks 42 at 1750 RPM would get it to 8.6 Knots (9.89 MPH). What I thought of as a more comfortable RPM of 1600 would do about 8.3 knots (.54 MPH). 10-13 MPH is inflated sales speak..
__________________
Rich Gano
FROLIC (2005 MainShip 30 Pilot II)
Panama City area
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08-07-2020, 09:31 AM
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#13
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Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,738
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Quote:
Originally Posted by Swfla
Thanks to you all. So many on this forum talk about running at 6-8 knots. The ones who run normally at 6 are just babying their gear and/or watching gph flow.
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If it’s fuel burn you’re worried about (you seem to be like many others) just keep shopping until you find a single engined GB36. Why do you need such a big boat?
Once you buy a big twin you’ll be reading fuel burn posts on and on. The problem is that the new buyers had a lot of money and fuel burn wasn’t an issue for them. But for normal people fuel economy is. You probably can’t even count all the threads on fuel burn. But now you’re in a position now to do something about it.
Some say fuel burn is only a small part of boating expenses. Depends on how you boat. Where you moor your boat, where you spend the night like anchored out eating grub from home or at a marina eating out upper end and head’in for other places after ect ect. But if you’re a low-buck boater fuel is a big issue. Why else would all these TF members stress and worry about fuel? And they do.
__________________
Eric
North Western Washington State USA
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08-07-2020, 09:39 AM
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#14
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Veteran Member
City: Safety Harbor
Vessel Name: Yankee Peddler
Vessel Model: Grand Banks Eastbay
Join Date: Jul 2014
Posts: 42
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GB hulls are not displacement boats. They can be pushed faster with more horsepower
A GB is considered a semi planning hull. With more horsepower you can get them to semi-plane along with a lot more fuel consumption. The old 1.3 times the waterline length was never a scientific formula. Sort of like the definition of a good investment is one that turns out that way.
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08-07-2020, 09:44 AM
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#15
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Guru
City: San Diego
Vessel Name: Circuit Breaker
Vessel Model: 2021..22' Duffy Cuddy cabin
Join Date: Oct 2007
Posts: 6,691
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Quote:
Originally Posted by Nomad Willy
Why do you need such a big boat?
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My god, Eric! That's what the man wants!
__________________
Done with diesel power boats! Have fallen in love with all electric!
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08-07-2020, 10:20 AM
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#16
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Guru
City: Southport, FL near Panama City
Vessel Name: FROLIC
Vessel Model: Mainship 30 Pilot II since 2015. GB-42 1986-2015. Former Unlimited Tonnage Master
Join Date: Oct 2007
Posts: 4,977
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Quote:
Originally Posted by Nomad Willy
Why else would all these TF members stress and worry about fuel? And they do.
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Not here anyway. I did not care about it with the 3.35 GPH at 9.5 MPH on the GB, thinking that it was fairly low, and I don't care about it at about 9 GPH at 16 MPH now because the last thing I want to do is spoil my fun on the water worrying of fuel burn rate.
__________________
Rich Gano
FROLIC (2005 MainShip 30 Pilot II)
Panama City area
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08-07-2020, 10:29 AM
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#17
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Senior Member
City: San Diego
Join Date: Jul 2020
Posts: 478
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Quote:
Originally Posted by Nomad Willy
If it’s fuel burn you’re worried about (you seem to be like many others) just keep shopping until you find a single engined GB36. Why do you need such a big boat?
Once you buy a big twin you’ll be reading fuel burn posts on and on. The problem is that the new buyers had a lot of money and fuel burn wasn’t an issue for them. But for normal people fuel economy is. You probably can’t even count all the threads on fuel burn. But now you’re in a position now to do something about it.
Some say fuel burn is only a small part of boating expenses. Depends on how you boat. Where you moor your boat, where you spend the night like anchored out eating grub from home or at a marina eating out upper end and head’in for other places after ect ect. But if you’re a low-buck boater fuel is a big issue. Why else would all these TF members stress and worry about fuel? And they do.
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You misread me. I'm not worried about fuel burn rate. I just wanted to know what the realistic cruise speed is. Sales postings, exaggerate too often. I gave a size range because I'd like to buy in my geographical area and need to be flexible to match availability. My boating skills are honed on twin engines. A single would be fine with a bow thruster. But again, it's availability or going into the yard for a bow thruster. I'm old enough to know my abilities on a single screw. Thanks for your post.
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08-07-2020, 10:32 AM
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#18
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Senior Member
City: San Diego
Join Date: Jul 2020
Posts: 478
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Thanks to a few GB 42 owners for sharing their experience.
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08-07-2020, 10:42 AM
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#19
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Guru
City: gulf coast
Join Date: Jun 2014
Posts: 3,440
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13 mph is 11.3 knots, way too fast for that boat. If it actually did go that fast it would be plowing waves and burning a lot of unnecessary fuel. Figure 8 Kts or so for reasonable cruising.
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08-07-2020, 10:46 AM
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#20
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Senior Member
City: San Diego
Join Date: Jul 2020
Posts: 478
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I think a good setup for me would be 36' with bow cabin and second cabin (aft likely). Twin engines like FL 80 or 120 hp or single cummins with bow thruster. Cruising at 8 knots is perfect. A genset is preferred but would consider an inverter setup with ample ah batteries for two days on the hook. Not likely to be more than 48 hours port to port. Don't need huge tanks. Still have a few life situations to get squared away but see myself ready in 12 months. Should give me time to read, look in person, join the power squadron once Covid is behind us. Then actively shop. In the meantime thanks for all the great members who share opinions and or knowledge.
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