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Old 10-04-2019, 05:29 PM   #101
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The boat I bought had twins, I added a bow thruster after 5 years. I need all the help I can get getting in and out of slips, or doing locks with wind and current.
If had a single and bow and stern thrusters it would be fine.

Cost and redundancy of twins are factors but insignificant.

I have limped to marinas on one motor more than once for fuel and mechanical issues. I Have unlimited towing and use that too.

Any boat you buy will have an operational learning curve no matter how it is configured. Single or twin your boat challenge will depend on wind, current and what you do with it, your skill set, the boats size, draft, maneuverability.

Buy the boat that checks your boxes and learn to love it.
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Old 10-04-2019, 07:17 PM   #102
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kind of ironic that the big benefit of twin screw maneuverability as touted here,also have bow and sometimes stern thrusters.
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Old 10-04-2019, 07:23 PM   #103
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Originally Posted by TwoToTango View Post
Ok I know this is an age old debate- Twin engines vs Single. . I know most of the stated advantages and disadvantages like more maneuverability and back up power for twins. I get that . But given two identical boats w a full displacement hull., one with a single Lehman 120 and the other with twin 120s , how much extra fuel do the twins use at say cruising speed of around 6 nts? Twice? My gues is not that much more but does anyone have some real experience to answer that for me ? Also just how often really end up using the twin in a back up situation ? Iíve been told if one goes down the other is likely because itís usually fuel issues that cause a diesel to stop . Thanks for your help . Just trying to educate myself. I like the idea of a single primarily because itís easy on fuel. Done really have desire to go fast.
s

Since I now have an Endeavour 44 Cat Trawler and previously had a Leopard 38 cat sailing vessel, there was no choice- twin engines. But the major advantage of twins in any boat is maneuverability and control. In a cat you can turn in your own length, easily back into the slip, dock, etc. my good friend has a Beneteau 44 Swift Trawler and the twins on her make her infinitely easier to handle. While the fuel consumption might be slightly higher, you have more power and more efficiency, plus if one engine fails you have a backup

No brainer for me
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Old 10-04-2019, 07:35 PM   #104
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kind of ironic that the big benefit of twin screw maneuverability as touted here,also have bow and sometimes stern thrusters.
In the 60's/70's all I ever piloted were single screw. Back then "thrusters" weren't discussed.

Since then, I've had boats with twins for quite some years. Enjoy the heck out of twin screw. Still, never had nor used a bow or stern thruster. Don't plan to ever do so.

I can handle a boat with a single. It's super easy with twins!
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Old 10-04-2019, 07:43 PM   #105
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When I did my re-power I considered the option of going to a single. As you can see in the pic, the keel was designed and built with a single in mind. But I'm not aware of any Mk1's that have a single.

I went with twins because the yard's quotes for the twins was cheaper, largely due to the higher cost of the larger HP single engine. Afterwards the broker I bought from said that it was a good thing I installed twins - in his words, had I installed a single I would never have been able to sell the boat.

I would have been comfortable with either route, and expected maintenance and fuel costs to be more or less the same, but market sentiment or bias definitely favours twins in the >45' size range.
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Old 10-04-2019, 11:49 PM   #106
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Originally Posted by TwoToTango View Post
Ok I know this is an age old debate- Twin engines vs Single. . I know most of the stated advantages and disadvantages like more maneuverability and back up power for twins. I get that . But given two identical boats w a full displacement hull., one with a single Lehman 120 and the other with twin 120s , how much extra fuel do the twins use at say cruising speed of around 6 nts? Twice? My gues is not that much more but does anyone have some real experience to answer that for me ? Also just how often really end up using the twin in a back up situation ? Iíve been told if one goes down the other is likely because itís usually fuel issues that cause a diesel to stop . Thanks for your help . Just trying to educate myself. I like the idea of a single primarily because itís easy on fuel. Done really have desire to go fast.
Rule Number 1 - Always have an alternative means of propulsion
Rule Number 2 - Remember Rule Number 1


That said I've come over to what most sailors would call the dark side - Grand Banks 36 - twin Lehman 120's. My previous boat was a Westsail 42 with a nice little Perkins when things got ugly or the wind died.



But Rule Number 1 and Rule Number 2 are still appropriate.


Fuel Economy - A good trawler with the right hull form will make hull speed pretty easily with either single or twin engines. Mine is a Grand Banks 36 with twin Lehman 120's. Fuel consumption is 2.8 GPH at 8 kts. And that's measured. Sorry to everyone out there - I'm an engineer.



So - this is my when the smelly sticky stuff hits the rotating device which it always does out on the water answer to 1 versus 2 engines. Fuel economy is transparent when the shit hits the fan.


Just my $0.02 for whatever it's worth.
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Old 10-05-2019, 01:39 AM   #107
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Originally Posted by PopeyeGB36 View Post
Rule Number 1 - Always have an alternative means of propulsion
Rule Number 2 - Remember Rule Number 1


That said I've come over to what most sailors would call the dark side - Grand Banks 36 - twin Lehman 120's. My previous boat was a Westsail 42 with a nice little Perkins when things got ugly or the wind died.



But Rule Number 1 and Rule Number 2 are still appropriate.


Fuel Economy - A good trawler with the right hull form will make hull speed pretty easily with either single or twin engines. Mine is a Grand Banks 36 with twin Lehman 120's. Fuel consumption is 2.8 GPH at 8 kts. And that's measured. Sorry to everyone out there - I'm an engineer.



So - this is my when the smelly sticky stuff hits the rotating device which it always does out on the water answer to 1 versus 2 engines. Fuel economy is transparent when the shit hits the fan.


Just my $0.02 for whatever it's worth.
Your calc = 2.86 nmpg.

As comparison...

Our 34' Tollycraft, flying bridge - tri cabin, with twin 350 cid Mercruisers gets:

1. Running one engine, at 4.5 to 5 knots... just shy of 3 nmpg.

2. Running twins, at 6.5 to 7 knots... just over 2 nmpg... [calced hull speed is 7.58 knots].

3. On full plane, doing 16 to 17 knots... she gets 1 nmpg.

We seldom run at #1 speed. Often run at #2. And, love to run at #3 when we want to save time getting some place.

Having 200 gallon tankage [considering 20% safety hedge; i.e. 40 gallons remaining fuel]:

#1 = 480 mile range
#2 = 320 miles
#3 = 160 miles

Another item I love about our planing hull Tolly is its 23 nmph at WOT... when required. That speed = OMG nmpg!!! Never gone that fast long enough to calc nmpg. As s guess, I'd have to take a stab at 0.5 nmpg??? That would only = 80 mile range. I'll never push her engines that hard [5400 +/- rpm] for that long.

Few times I've hit WOT were for few minutes each. Things like equipment testing purposes and a couple times we simply needed to alter our position due to other boats' incorrect actions.
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Old 10-05-2019, 10:50 AM   #108
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Single vs twin.

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Originally Posted by TwoToTango View Post
Are you saying there are other advantages to a single? Maintenance costs?
I have a very competent mech perform the annual svc on my single 120, transmission and generator for several reasons. As an aside, while I could do it, he probably saved me $30,000 this year by finding hidden problems I would never have discovered doing the std service myself. I digress. Annual svc for 1 engine, xmission and gen is $1,000. You can almost double that for 2 (almost since there would still only be 1 gen). Every so often thereís the matter of stuffing box and cutlass bearing. Double that for two engines.

Additionally, I can literally walk (crawl) all the way around my engine and everything on it is very accessible. Thatís a huge benefit. And yes, generally speaking, Diesel engine failures are usually fuel related, which means that second engine isnít going to help you. This isnít always the case but it usually is. I donít know what handling like on 1 engine when the other fails on a displacement hull but I imagine itís pretty bad.

I have 1 engine, no thrusters. Backing is always an adventure and here, two engines would be nice, but not enough to justify the downside of having 2.

When I was in the market for my boat 1 engine was a requirement.

Having said all that, in my opinion fuel cost should not even be on the radar screen when deciding between 1 or 2. Listen to the 2 engine guys and their reasoning and experience and then decide which philosophy fits your needs.

Finally, there is a saying in aviation. ďThat second engine gets you to the accident scene fasterĒ.
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Old 10-05-2019, 11:08 AM   #109
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Quote:
Originally Posted by PopeyeGB36 View Post
Rule Number 1 - Always have an alternative means of propulsion
Rule Number 2 - Remember Rule Number 1


That said I've come over to what most sailors would call the dark side - Grand Banks 36 - twin Lehman 120's. My previous boat was a Westsail 42 with a nice little Perkins when things got ugly or the wind died.



But Rule Number 1 and Rule Number 2 are still appropriate.


Fuel Economy - A good trawler with the right hull form will make hull speed pretty easily with either single or twin engines. Mine is a Grand Banks 36 with twin Lehman 120's. Fuel consumption is 2.8 GPH at 8 kts. And that's measured. Sorry to everyone out there - I'm an engineer.



So - this is my when the smelly sticky stuff hits the rotating device which it always does out on the water answer to 1 versus 2 engines. Fuel economy is transparent when the shit hits the fan.


Just my $0.02 for whatever it's worth.
Hi. I have a GB 36 Classic with 1 120. Hull number 712. What is yours?
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Old 10-05-2019, 11:23 AM   #110
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IMHO - forget gas. 30 years made me a diesel believer (after 20 years of gas).
Get a T dock and maneuverability becomes moot for most of your experiences.
Put a little extra into maintenance (still not equal to twins) and you should be fine.
A "get home" engine or genset attachment would be nice. Get experienced recommendations for onboard spares and keep a lot (cheap insurance). Definitely join Boat US insurance for underway, anchoring failures FOR SURE
Good Luck - with your forethought you'll have lots of fun (and some terror as well)
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Old 10-05-2019, 11:26 AM   #111
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Oh Yeah ! Reduce your "fuel expense" concern, fuel cost will become a small percentage of your boat ownership. Personal experience taught me that the more you can competently do yourself is your BEST cost reducer.
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Old 10-05-2019, 11:28 AM   #112
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2. While I have never used a twin engine as back up for an engine failure, you might also ask how many of those of us with singles have had an engine failure that left us stranded. In 30 years of operating single engine diesel boats, I have had that happen once.
For newer boats with electronic engines this becomes more problematic. These engines are software controlled and have tons of sensors. They are designed to shut down (or in some cases de-rate) rather than hurt themselves.

So for example my engines have a seawater outlet pressure sensor. Why, I cannot fathom. Stupid. Anyway they are failing all over the country. When it fails, the ECU in all it's wisdom shuts down the engine.

Was quite glad I have two engines when it happened to me!
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Old 10-05-2019, 11:57 AM   #113
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Personal Experience....
IF I didn't have spares aboard, or good drill/easy out capability, patience to deal with multiple engine flameouts a day due to fuel system air ...in busy waterways, etc....


Issues I have had in 18,000 miles and 3,600 eng hrs and last 8 years of cruising.



1. Fuel pipe pin hole on 1000 hr pipes. Massive atomized spray...could have been a fire to those less experienced.
2. Fuel pipe crack on 2000 hr pipes. Could have been a manufacturing defect or the need to bend it a bit more than designed.
3. Alternator bracket bolt sheer.... required through drilling with cobalt drills and replacement bolt.
4. Bubbles in coolant suggesting head gasket replacement.
5. Dampner plate failure stopping engine cold in a bad seaway.

6. Multiple engine shutdowns due to elusive air in fuel system.
7. Alternator failure/engine lug to alternator adjuster arm failure. Difficult to find/replace lug.


Some of these could have been avoided with better engine history from the PO. Maybe. All can happen even with experienced, liveabord, active cruiser eyes watching things.


Do I hate single engine? Naw...the gasser on my towboat was actually more reliable.


So much for Lehmans being "bullet proof"...sure maybe the block is but you are at the mercy of marinizing manufacturer after market parts sometimes.


If Sea Tow or BoatUS wasn't available in the areas I cruise...my experience would have me leaning twin....not for any other reason though.
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Old 10-05-2019, 12:30 PM   #114
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So for example my engines have a seawater outlet pressure sensor. Why, I cannot fathom. Stupid. Anyway they are failing all over the country. When it fails, the ECU in all it's wisdom shuts down the engine.

Was quite glad I have two engines when it happened to me!
I'm not familiar with that particular sensor...what was the fix, (other than replacing it.)
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Old 10-05-2019, 12:40 PM   #115
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Guess I just love old-school simplicity!

In all the power vehicles I list below... the only one that can be an expensive PITA is the last one - because - although it's a comfortable classy rig... it's all computer interfaced and chips/features go south way too often [currently in shop for new chips and new backup camera = $1,200, and, something I could not have sussed out and cannot accomplish]. The rest of the rigs I maintain well... they breakdown very seldom. Mostly I can repair breakdowns and if expert assistance becomes necessary it usually does not cost an arm and a leg.

Vehicles we have:

1 - 1967 Buick Wildcat, AT with nearly all options inc tilt wheel, electric seat/windows and AC w/ 430 cid, 400 hp engine [5 years ago, at 125K miles I had her rebuilt by an expert - jacked-up her power range from factory original 360 HP to around 400 HP] - 4 bbl Rochester with enlarged internal fuel ports. Increased air intake, Twin 2" straight exhaust pipes with V-crossover pipe and low restriction mufflers - A good sounding, real screamer - See photo.
1 - 1977 Tollycraft tri cabin w/ twin Mercruiser 350 cid, 255 HP engines, single 7.5 kW Kohler gen set... all 3 carbed
1 - 1975 Crestliner fast runabout 15' 4-seater, canvas top, full windshield; a cool tow behind w/ 50 HP Johnson - carbed
1 - 1985 Chevy Cheyenne 1 ton, 4WD, 4 spd, geared transfer box, 4" lift, reg cab, power everything, AC'd, LB pickup w/ 350 cid 325 hp GM engine - Carbed
1 - 1989 19' Bluewater ski boat, cuddy cabin w/ Mercruiser and I/O drive - TBI fueled
1 - 1996 25'6" Tiffin Allegro motorhome w/454 Chevy engine - TBI fueled
1 - 1998 Ford Explorer SUV 4WD w/ 6 cyl - EFI fueled
1 - 2014 Lincoln MKT SUV, 4WD and nearly every option w/ 375 hp - EFI - A screamer!
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Old 10-05-2019, 04:39 PM   #116
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This post will never end.....
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Old 10-05-2019, 04:40 PM   #117
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kind of ironic that the big benefit of twin screw maneuverability as touted here,also have bow and sometimes stern thrusters.
Never had a bow or stern thruster. I have had singles and twins. And, I admit, it's a lot funner parking a twin!
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Old 10-05-2019, 05:33 PM   #118
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Mooring a twin I do while napping.... a single takes a bit of seamanship in some cases.
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Old 10-06-2019, 07:43 AM   #119
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Mooring a twin I do while napping.... a single takes a bit of seamanship in some cases.
Our last single, a 42 foot sailboat, would only back 20 to 40 degrees to port, so when it was time to back into a slip, you had to have it positioned where those numbers put you into the slip (or wherever you wanted to back up to).
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Old 10-06-2019, 08:59 AM   #120
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twin vs single

I owned a GB 36 with a single engine, no BT for 6 years and have owned a MS 34 trawler with twins for 3 yr. Although this may never happen, when faced with a choice between twins or single with a BT I would go with the boat in the best condition with price always a consideration. The reason I went with the twins was the boats availability at the time and its condition. Never consider a single lacking a thruster!! I know the old salts of the world will see this as a reduced hormone level on my part but try a 30mph cross wind with a margin of error of less than 2 ft some time with the single no BT!
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