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09-25-2019, 11:15 AM
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#1
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Senior Member
City: Lagrange, IL
Vessel Name: Moondance
Vessel Model: Grand Banks CL 42
Join Date: Sep 2019
Posts: 170
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Engine choice on Grand Banks 42
Investigating the GB 42. It really has a wide range of engine options. One brokered boat advertises twin Ford 135 HP with a cruise speed of 7kts and a max of 8kts. But I corresponded with a broker on another boat, same engines, and says cruise speeds of 9 to 12 kts. What can I really expect with the NA 135hp engine.
Additionally I read the V8 engines take up a lot of space compared to the in-line engines. So how hard is it to work on these V8's? I plan on doing as much maintenance as I can myself.
Thanks for your inputs.
Pat
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09-25-2019, 11:25 AM
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#2
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Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,603
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I would suspect closer to 9-10 knots WOT but go out on a test ride and see.
Seeing is believing but you’ll get many opinions here. Perhaps 10 knots.
First opinion.
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Eric
North Western Washington State USA
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09-25-2019, 11:34 AM
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#3
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Guru
City: Vallejo, California
Vessel Name: Mahalo Moi
Vessel Model: 1986 Grand Banks 42 Classic
Join Date: Jun 2008
Posts: 2,074
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I have Cat 3208, naturals. V8s. I don’t like it, but I’ve always been able to perform maintenance; raw water pumps, etc.
Cruising at 1800 rpm gives me about 8.5 to 9.0 kts. Our chosen speed is really more a function of hull shape as opposed to horsepower. Sure, I can push the boat (and a wall of water!) to 12 to 14 kts. However, my fuel consumption increases from 6 gph (sum of both engines) to, who knows, 18 to 20 gph. I like to smell roses!
__________________
Ray
"Mahalo Moi"
1986 GB-42 Classic
ΜΟΛΩΝ ΛΑβΕ
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09-25-2019, 11:34 AM
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#4
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Senior Member
City: Out and About
Vessel Model: Sold-GB 52 Europa, Queenship 59, Tolly 45
Join Date: Nov 2016
Posts: 484
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Cruise speed with twin 135hp will be 7-7.5 knots.
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09-25-2019, 12:20 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: 18,033
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No way will you get a 12 knot cruise out of 135s. I would bet between 7 and 8 knots will be a realistic cruise speed. If you are going with a trawler then in the range of 7 to 9 knots is a reasonable cruise. We have SP225 Lehmans in a 41’ and cruise at about 8.5 knots at 1400 RPM. Our full throttle is 17 knots.
__________________
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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09-25-2019, 12:27 PM
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#6
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Guru
City: Narragansett Bay
Vessel Model: Grand Banks 36
Join Date: Sep 2016
Posts: 1,649
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270 (total hp) will not push that boat much over hull speed...if at all. And then it will be producing lots of black smoke. Hull speed is about 8.5 knots. That boat will cruise nicely at 8 knots at 1/2 throttle.
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09-25-2019, 12:47 PM
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#7
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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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I have a 42 grand banks with twin Lehman 135s, MG5011 twin disc transmissions with a 2.44:1 reduction, not over-propped.
With a clean hull we cruise between 8 and 8.3 knots with engine RPM between 1700 and 1750.
WOT yields 2600 RPM loaded, but our throttle limit screws are turned back to where we max out at 2300 RPM.
2300 RPM yields a speed of 11 knots without the faintest haze of black smoke.
The Lehman 135 is not a V8, it's an inline V6. It's incredibly easy to work on, and while they are large, so is the engine room.
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09-25-2019, 12:50 PM
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#8
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Guru
City: Narragansett Bay
Vessel Model: Grand Banks 36
Join Date: Sep 2016
Posts: 1,649
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Quote:
Originally Posted by Westiculo
I have a 42 grand banks with twin Lehman 135s, MG5011 twin disc transmissions with a 2.44:1 reduction, not over-propped.
With a clean hull we cruise between 8 and 8.3 knots with engine RPM between 1700 and 1750.
WOT yields 2600 RPM loaded, but our throttle limit screws are turned back to where we max out at 2300 RPM.
2300 RPM yields a speed of 11 knots without the faintest haze of black smoke.
The Lehman 135 is not a V8, it's an inline V6. It's incredibly easy to work on, and while they are large, so is the engine room.
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Very “artsy” looking Lehman’s
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09-25-2019, 06:29 PM
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#9
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Senior Member
City: Lottsburg, Va
Vessel Name: Amazing Grace
Vessel Model: Ocean Alexander 52 Sedan
Join Date: Dec 2007
Posts: 312
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We had a 42 powered by in line 6cyl 315hp Cummins. She liked to cruise 1750 -1800 rpm and made 9.5 kts. Fast cruise was 12-14 kts, fuel burn jumped from 5 mph. WOT was 17.5 kts, it looked like much larger vessel was creating that wake, but we could roll over the bow wave and actually get on plane. Only did that on rare occasions; sea trial at sale was one. God knows what the fuel burn was at that speed, I did notice that we'd increase speed just a bit if we held WOT for 15 minutes; lighter fuel load I guess.
Plenty of space to get around in the ER.
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09-25-2019, 06:41 PM
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#10
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Guru
City: Everett, WA
Vessel Model: Ocean Alexander 38'
Join Date: Oct 2007
Posts: 756
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Quote:
Originally Posted by Westiculo
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The Lehman 135 is not a V8, it's an inline V6. It's incredibly easy to work on, and while they are large, so is the engine room.
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Never heard of an inline V6, or is it an inline 6?
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09-25-2019, 06:46 PM
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#11
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Guru
City: Palm Coast, FL
Vessel Name: Coquina
Vessel Model: Lagoon 380
Join Date: Jan 2017
Posts: 2,476
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He meant L6 or I6. And where does the L come from anyway?
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09-25-2019, 07:17 PM
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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: 4,550
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The hull speed of my GB42 was 8.6 knots and for years I ran my twin Lehman 120s with 2.01:1 and 1.91:1 trannies at 1800 RPM getting exactly that speed. Eventually, I found that 1600 RPM was a vert sweet and quieter spot for those particular engines at 8 knots on the nose. Any more power in this hull is just not necessary unless you are planning to waste a lot of fuel to achieve marginal speed increase.
__________________
Rich Gano
FROLIC (2005 MainShip 30 Pilot II)
Panama City area
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09-25-2019, 07:28 PM
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#13
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Senior Member
City: Phoenix, AZ
Vessel Name: Enigma
Vessel Model: 1997 Wellcraft Excel 26 SE
Join Date: Mar 2015
Posts: 282
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Quote:
Originally Posted by diver dave
He meant L6 or I6. And where does the L come from anyway?
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I = inline
L = line
Besides V there are a lot of other configurations. (W, H, U, flat) However none that I know of in the marine world.
__________________
>>>>>>>>>>>Action
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09-25-2019, 10:11 PM
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#14
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TF Site Team
City: Saltspring Island
Vessel Name: Retreat
Vessel Model: C&L 44
Join Date: Nov 2007
Posts: 5,461
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Quote:
Originally Posted by gsholz
Cruise speed with twin 135hp will be 7-7.5 knots.
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I frequently cruise with a friend who has that boat. I go 8.0 all the time. He waits for me.
__________________
Keith
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09-25-2019, 10:22 PM
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#15
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Senior Member
City: Lagrange, IL
Vessel Name: Moondance
Vessel Model: Grand Banks CL 42
Join Date: Sep 2019
Posts: 170
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Thanks guys. Good info on the straight 6's which I know the Lehman's are. You confirm what I have been told about the ease of working on this type of engine.
Giggitoni also confirms the tightness of the V8's ER. As I scour the internet for a boat to purchase I'm seeing more V8's in the GB42's than other options so thus my curiosity about being able to work around them. Some even have stabilizers and that too seems to cut down on maneuverability down below.
I guess if I had my choice I would want a set of the more powerful straight 6's but as we all know everything is a compromise. Give me a real clean, well priced boat with V8's and I might have to buy it.
Please keep your real world stories coming. I need all the knowledge I can get in this daunting task of finding a boat.
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09-26-2019, 06:34 AM
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#16
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Guru
City: Rochester, NY
Vessel Name: Hour Glass
Vessel Model: Chris Craft 381 Catalina
Join Date: Aug 2019
Posts: 6,091
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Even if the engine room looks tight, when you go to look at a boat, crawl in there and see where the common service points on the engines are. It may turn out that either the tight spots aren't as bad as they look or that you rarely have a need to crawl in there and it's not a big deal. Or it may be possible to add a hatch for better access.
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09-26-2019, 08:51 AM
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#17
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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 Giggitoni
Cruising at 1800 rpm gives me about 8.5 to 9.0 kts. Our chosen speed is really more a function of hull shape as opposed to horsepower.
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Ray, Is that your tender I see in your avatar?
__________________
Done with diesel power boats! Have fallen in love with all electric!
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09-26-2019, 10:00 AM
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#18
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Guru
City: Vallejo, California
Vessel Name: Mahalo Moi
Vessel Model: 1986 Grand Banks 42 Classic
Join Date: Jun 2008
Posts: 2,074
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Quote:
Originally Posted by Codger2
Ray, Is that your tender I see in your avatar? 
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That’s right, Walt! I drag him around a lot.  The tender also has a well-stocked frig!
__________________
Ray
"Mahalo Moi"
1986 GB-42 Classic
ΜΟΛΩΝ ΛΑβΕ
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09-26-2019, 10:01 AM
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#19
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Guru
City: Annapolis
Vessel Model: 58' Sedan Bridge
Join Date: Aug 2013
Posts: 6,467
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Quote:
Originally Posted by Pat T
I guess if I had my choice I would want a set of the more powerful straight 6's but as we all know everything is a compromise. Give me a real clean, well priced boat with V8's and I might have to buy it.
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I don't know that boat or those engines, but the probable hull length at the waterline (40'?) suggests a maximum comfortable cruise speed would be 8.5 kts in "displacement mode"... i.e., not counting any semi-planing a boatload of additional horsepower (and fuel) might allow.
-Chris
__________________
Chesapeake Bay, USA
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09-26-2019, 10:07 AM
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#20
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Senior Member
City: Mahón, Menorca
Vessel Name: Halcyon
Vessel Model: 1973 Grand Banks 50
Join Date: Mar 2015
Posts: 430
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I find "cruising speed" has as much to do with the choices the helmsman makes as with the boat and the motor in question.
I had a Grand Banks 42 with twin 120 hp Lehman-Fords which I tended to run at 1600 RPM achieving 8.5 knots. WOT achieved 11 knots.
Over time, though, I realised how fuel consumption-per-mile jumps with each additional knot so I have slowed down.
I now have a Grand Banks 50 with twin 250 hp General Motors V-8s. I can comfortably cruise at 9 knots but, to save fuel I mostly cruise at 7 knots, sometimes as low as 6.5 knots.
Call me cheap :-)
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Gilberto
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