1 vs 2 diesels, insights please..

[sunchaser]

True dat.....I don't recall anyone stating the rudders should be moved from their center position, meaning I don't recall anyone suggesting rudders be used in close quarters
Peter

Peter
Using rudders on twins when docking is pretty standard if you’ve no stern thruster. Yup, I said “rudders” over in post 127. Even Chapman says use rudders. Rudder use on twins for maneuvering is boating 101 and has been for likely a century or more.

But as Koliver said, lots of cruisers with twins lack some skills. Same applies to singles. We’ve quite a few in our marina that use their bow thruster to make turns in the fairway.

 

[psneeld]

Peter
Using rudders on twins when docking is pretty standard if you’ve no stern thruster. Yup, I said “rudders” over in post 127. Even Chapman says use rudders. Rudder use on twins for maneuvering is boating 101 and has been for likely a century or more.

But as Koliver said, lots of cruisers with twins lack some skills. Same applies to singles. We’ve quite a few in our marina that use their bow thruster to make turns in the fairway.

Yeah .... true enough, but I see Peter's point about instruction, when teaching newbies, getting them to center the rudders and hands off the wheel keeps them focused on proper engine use which will usually be enough to get the job done. As one gets more experience.... the rudders are obviously in play and sometimes a necessity.

 

[SteveK]

Peter
Using rudders on twins when docking is pretty standard if you’ve no stern thruster. Yup, I said “rudders” over in post 127. Even Chapman says use rudders. Rudder use on twins for maneuvering is boating 101 and has been for likely a century or more.

But as Koliver said, lots of cruisers with twins lack some skills. Same applies to singles. We’ve quite a few in our marina that use their bow thruster to make turns in the fairway.

Not until I read on this forum did I force myself to not use rudders and to leave them centered. Doable, but harder to move the boat where you want it. Yet, you can steer twins without a rudder.
But then I have docked a sailboat under sail and onetime backwards.
Simply, do not drive it like a car, be one with the boat and feel/see/anticipate the movement and where momentum will stop.

 

[klee wyck]

I currently own and drive one of each, single and twins.
The single with bow thruster only is a little easier for me to handle in close quarters than the twins with no thrusters, but not enough to worry about.
If or when buying another boat, I would be pretty agnostic on the issue despite the nearly 150 posts on the matter here.

 

[mvweebles]

I currently own and drive one of each, single and twins.
The single with bow thruster only is a little easier for me to handle in close quarters than the twins with no thrusters, but not enough to worry about.
If or when buying another boat, I would be pretty agnostic on the issue despite the nearly 150 posts on the matter here.

Good post from an experienced owner.

Despite it being a well-worn topic, thread has influenced me. I can tell you what I like about my Willard 36, but in all candor, the reason I bought her 25+ years ago is I just fell in love with her - when I walked aboard, I immediately turned to my other half and said "Well, this boat is sold. Only question is price." This was early in the Internet days and I was much less experienced - Beebe influenced me so I was definitely on track for long distance trek-capable boats, but I cannot honestly say why I fell head-over-heels. It wasn't because she's a single, though I really like long keel singles. Might have been because of the canoe stern - Cheryll (other-half) likes to say "real boats have round butts." I'm good with that.

To Klee Wyck's point, if I were to start the search today with same dream, I don't know where I'd end up. Single v Twin would not be a deal killer as long as the boat was suitably maneuverable and access for maintenance access was reasonable. Range is a big thing for me so the size of engine(s) may matter; plus I really like cruising at jogging speed. Much as I like GB36s, buying one with twin 375hp diesels would not work for me. A single FL120 would; and a pair of FL120s would be workable.

"You dance-with-who-you-brung." I think an owner will adapt to a single or twin as long as they are (twins) reasonably accessible for maintenance; and (singles) reasonably maneuverable. There are deal breakers, but, within reason, engines are not one. For me - I hate external wood so teak decks. Stabilization is another.

In the end, I think you have to prioritize deal-killers, strong preferences, preferences, and heart-goes-pitter-patter items (the round-butt thing for my other half). Maneuverability, range, maintainability, reliabilty are on that list somewhere, but single/twin engine is not except as a means-to-the-end.

Peter

 

[BruceK]

I routinely use the rudders when maneuvering a twin in tight quarters. It increase the rate of pivot and changes the pivot point. Both very useful once understood and practiced.

Agreed. Try rotating your twin engine boat using reverse and fwd without rudder, then with rudder. It`s convincing.
But coming in to dock, using rudder adds another task at a busy time, I avoid it unless necessary. Sometimes the boat doesn`t want to spin up perpendicular to the dock to reverse in(?current), so I add rudder. Concentrating, I can forget to take it off, interestingly it seems not to affect control/direction reversing in. Probably due to the low speed of water over rudder,and maybe undersized rudders.

 

[tiltrider1]

If or when buying another boat, I would be pretty agnostic on the issue despite the nearly 150 posts on the matter here.

Total agreement.

The boat and the mission are more likely to dictate weather I had a single or a twin.

 

[mvweebles]

Agreed. Try rotating your twin engine boat using reverse and fwd without rudder, then with rudder. It`s convincing.
But coming in to dock, using rudder adds another task at a busy time, I avoid it unless necessary. Sometimes the boat doesn`t want to spin up perpendicular to the dock to reverse in(?current), so I add rudder. Concentrating, I can forget to take it off, interestingly it seems not to affect control/direction reversing in. Probably due to the low speed of water over rudder,and maybe undersized rudders.

In my opinion, prop-walk is a more important tool than rudders, even for a twin. Some time back, Rslifkin gave the best perspective I've seen: drive a twin as if it's two singles. Combination of both prop-walk and rudders, along with judiscious use of throttles and gears, is a toolbox.

The above said, using rudders with a twin can be challenging. It can be easy to forget where the are. When forward thrust is applied, results can be a surprise.

Peter

 

[sunchaser]

The above said, using rudders with a twin can be challenging. It can be easy to forget where the are. When forward thrust is applied, results can be a surprise. Peter

Knowing where your rudders are is pretty simple with the rudder angle indicator about 3’ from me. That said, as Bruce mentions smaller rudders can prove less effective.

 

[slowgoesit]

Okay Peter, I'm going to throw a wrench into the works. Our boat ONLY prop walks to starboard! Doesn't matter if in reverse, or forward . . . . makes it difficult to maneuver in close quarters sometimes . . . . and no, I'm not mistaken.
Anyone want to take a stab at why? No fair reading my other threads either!

 

[mvweebles]

Okay Peter, I'm going to throw a wrench into the works. Our boat ONLY prop walks to starboard! Doesn't matter if in reverse, or forward . . . . makes it difficult to maneuver in close quarters sometimes . . . . and no, I'm not mistaken.
Anyone want to take a stab at why? No fair reading my other threads either!

I assume you have a single with a left hand prop (CCW in forward when viewed from astern). There is prop walk in forward, but it's overwhelmed by wash over the rudder. In reverse, prop bites and pulls stern to the right. When you approach a side-tie, you probably approach at a 30-45 degree angle to land to starboard. As you are close, you go to reverse which engages prop walk and sucks the stern to the side tie while simultaneously slowing the boat, maybe applying a few "burps" of throttle to control speed.

Twins have counter-rotating props. Almost always the starboard engine has a right handed prop, port engine a left handed prop. The same side-tie landing is done but only with port engine into reverse which engaged prop walk to pull stern towards the dock. Usually, it's not necessary to "split the gears" (right engine in forward, left engine in reverse), but only use engine furthest from the dock - the left engine - in reverse.

But a twin is ambidextrous - it can land to port equally well by reversing the sequence.

Peter

 

[PierreR]

Slowgoesit, I am guessing with a Beebe design the boat has a controllable pitch propeller.

 

[psneeld]

Okay Peter, I'm going to throw a wrench into the works. Our boat ONLY prop walks to starboard! Doesn't matter if in reverse, or forward . . . . makes it difficult to maneuver in close quarters sometimes . . . . and no, I'm not mistaken.
Anyone want to take a stab at why? No fair reading my other threads either!

If I remember correctly, don't you have a variable pitch prop?

 

[mvweebles]

If I remember correctly, don't you have a variable pitch prop?

Rereading slowgoesits post, this makes sense. But prop walk should be considerably less noticeable in forward due to rudder wash overwhelming effect of prop walk.

Peter

 

[psneeld]

Prop wash in my experience is most noticeable when first stating to move and low throttle where the rudder has the least effect, but that has a lot of variables also. Probably why experience, especially with each boat, often causes the handler to use bursts of throttle to use that prop wash effectively.

 

[sunchaser]

Having watched Slow Goes It maneuver around the docks a few times I'd say he has his setup with big rudder, CPP, big prop and single pretty well figured out. Each vessel is a little different and sometimes leaving the dock and returning a few times in different conditions is instructive. Kinda like touch and goes or going to the driving range ???

 

[mvweebles]

I have only driven one boat with CPP. A Dreadnaught 32 sailboat (full keel) with a tiny diesel that was impossible to maneuver for a variety of reasons unrelated to the CPP. The very long bow sprit didn't help. It did help brush-up on use of springlines.

And then there is the odd builders' mistake. I gave a lesson once to a guy who was really miserable about his inability to dock his twin screw 40-footer. Turns out the props didn't counter-rotate. I was on an early Diesel Duck 38 that only had a portside PH door but had a LH prop meaning it walked to starboard making single handing incredibly awkward.

But I'd say 80% of the boats are fairly predictable in handling characteristics. Not saying they handle well, but you have a strong sense of what they will and won't do before you fire-up. But that 20% can really keep you honest.....

Peter

 

[rslifkin]

In my opinion, prop-walk is a more important tool than rudders, even for a twin. Some time back, Rslifkin gave the best perspective I've seen: drive a twin as if it's two singles. Combination of both prop-walk and rudders, along with judiscious use of throttles and gears, is a toolbox.

The above said, using rudders with a twin can be challenging. It can be easy to forget where the are. When forward thrust is applied, results can be a surprise.

Peter

I think the suggestion of a twin being 2 singles with really bad prop walk tied together came from someone on here originally. Once I thought about it a bit, I realized it was a great description. I see a lot of people try to run a twin by doing things like "go forward, stop, spin, stop, back into slip". Using 1 engine at a time often can give a much smoother result. Done correctly, you can start your turn while stopping the boat and just smoothly transition into a slightly curved reverse entry into a slip.

Many people are also not comfortable steering a twin in reverse, so they try to just back up perfectly straight. With a single, it's down to how much speed you need for rudder authority in reverse or ability to back and fill effectively, but a twin will steer in reverse at any speed with appropriate technique. Starting with both engines in reverse, you take one out of gear to turn towards that side. If you need to tighten the turn, give the engine you're turning towards a quick tap of forward thrust (not enough to slow the boat down too much, but prop walk and the off center thrust will kick the stern over noticeably).

That same prop walk can be very handy when departing a dock. With no bow thruster and a pivot point forward of center, I find it's often easier to back my boat off a face dock vs leaving bow first. It's much easier to slide the stern sideways off the dock than to try to get the bow swung out (and the shape of the boat gives more clearance for backing out anyway).

And yes, not having a rudder indicator adds some risk to using rudder in close quarters. You definitely have to keep on top of where the rudders are to avoid unexpected results. Twins with prop tunnels are more likely to need rudder use, as the tunnels significantly reduce prop walk.

Honestly, the biggest thing anyone ever told me that helped when maneuvering any boat (single or twin) is this: "You're not trying to force the boat to do something now. You're adding inputs to adjust what the boat is already doing." I see a lot of people just lean on the throttles to make the boat do something "right now" when they could get better results from a smoother, calmer technique.

 

[SteveK]

.......Twins with prop tunnels are more likely to need rudder use, as the tunnels significantly reduce prop walk......

Interesting, I had not noticed any difference. But then I make the boat do what I want and may be instinctually compensating with other tweaks to overcome.

Rudder use on singles or twins has a noticeable affect when a burst of throttle is applied going forward.

 

[psneeld]

I have run boats with tunnels, small props and rudders and long length to shaft separation ration where twisting with twins was almost impossible. The 2001-2003 timeframe Sea Ray 38 gassers were one of the worst for this.

When trying to maneuver with an engine out, almost impossible in anything but perfect conditions.

 

[SteveK]

I have run boats with tunnels, small props and rudders and long length to shaft separation ration where twisting with twins was almost impossible. The 2001-2003 timeframe Sea Ray 38 gassers were one of the worst for this.

When trying to maneuver with an engine out, almost impossible in anything but perfect conditions.

Glad you said 'almost'

 

[psneeld]

Glad you said 'almost'

Well anything is possible, but most have trouble with well handling boats.

You ever run one of those vintage Sea Ray 38's?

 

[Portage_Bay]

...
With no bow thruster and a pivot point forward of center, I find it's often easier to back my boat off a face dock vs leaving bow first. It's much easier to slide the stern sideways off the dock than to try to get the bow swung out (and the shape of the boat gives more clearance for backing out anyway)

I find it easier and more effective to spring the stern out rather than the bow. Often with twins no spring needed unless wind or current pin me to the dock. After I've pulled out of or off of the dock going asten in some conditions I will continue astern until in the fairway. Less stressful than turning 180 is tight quarters especially if wind and current are running. Once comfortable with operating the boat astern, single or twin, thrusters or no, it becomes a great tool to have in your boat handling tool box.

....
Honestly, the biggest thing anyone ever told me that helped when maneuvering any boat (single or twin) is this: "You're not trying to force the boat to do something now. You're adding inputs to adjust what the boat is already doing." I see a lot of people just lean on the throttles to make the boat do something "right now" when they could get better results from a smoother, calmer technique.

Excellent advice. I've been asked at times by crew "Why did you do that?" My answer is "Because that's what the boat wanted to do." That is, when it all works out. If it doesn't? I try to leave myself enough room and time for a "go around".

 

[SteveK]

Well anything is possible, but most have trouble with well handling boats.

You ever run one of those vintage Sea Ray 38's?

Have not.

 

[Cold Duck]

Just an observation, typically, 2 engines will run 4 times the cost to operate, not double over a single. Not saying this is bad, but it seems to be more realistic from an analytical standpoint. There are all kinds of statistical studies, reasons, etc, but this just seems to be the real world numbers. Also, down times increase. Again, not saying these are reasons not to go twin, just issues to consider. The way you use your vessel will dictate whether these issues are significant or not. Most vessels spend 90% of their life (or more) sitting in a berth. That's totally different than a long distance cruiser's usage. Coastal cruising in the US is going to be much safer with an engine failure than say traveling to Hawaii or Tahiti. Don't base your needs looking at commercial fishing boats in the Bering sea when your big adventure might be doing the GReat Loop or the ICW. I'm mostly river/bay/close coastal cruising now so engine failures are of no real concern, just throw out the anchor and call Sea Tow. I had a planned voyage Calif to Hawaii in 50hp Willard with sails as backup. Doing that trip at proper time of year was totally safe. But a trip like that needs a lot of planning and back ups. Take a real hard look at what you are going to use your vessel for, not necessarily your dreams that are not really ever going to materialize. But keep dreaming, that's always fun!

 

[Marco Flamingo]

One of the things I often see when somebody is having trouble is they're misjudging the boat's direction based on its apparent heading, forward or reverse, but more so in reverse. It is possible that the stern looks to be headed off in a bad direction, but because of wind, prop walk, offset twins, etc., it is actually crabbing and only looks like things are going wrong. If you have too much speed on, or think docking should only take 10 seconds, you might not have time to gauge the boat's actual direction or swing. "Correcting" what only appears to be a bad line then makes things worse.

A boat owner on the finger across from me must hold the record for stern and bow thruster bursts to get into his slip. It's a Ranger Tug or look-alike about 32 feet. Turns on a dime, but it takes him at least a dollar to get into his slip. Maybe he heard that docking a single can only be done with bow and stern thruster controls worked like a backhoe operator. I get in way faster even though I go slower. And with no yelling.

 

[rslifkin]

Just an observation, typically, 2 engines will run 4 times the cost to operate, not double over a single.

How do you figure that one?

 

[mvweebles]

I think the suggestion of a twin being 2 singles with really bad prop walk tied together came from someone on here originally. Once I thought about it a bit, I realized it was a great description. I see a lot of people try to run a twin by doing things like "go forward, stop, spin, stop, back into slip". Using 1 engine at a time often can give a much smoother result. Done correctly, you can start your turn while stopping the boat and just smoothly transition into a slightly curved reverse entry into a slip.

Many people are also not comfortable steering a twin in reverse, so they try to just back up perfectly straight. With a single, it's down to how much speed you need for rudder authority in reverse or ability to back and fill effectively, but a twin will steer in reverse at any speed with appropriate technique. Starting with both engines in reverse, you take one out of gear to turn towards that side. If you need to tighten the turn, give the engine you're turning towards a quick tap of forward thrust (not enough to slow the boat down too much, but prop walk and the off center thrust will kick the stern over noticeably).

That same prop walk can be very handy when departing a dock. With no bow thruster and a pivot point forward of center, I find it's often easier to back my boat off a face dock vs leaving bow first. It's much easier to slide the stern sideways off the dock than to try to get the bow swung out (and the shape of the boat gives more clearance for backing out anyway).

And yes, not having a rudder indicator adds some risk to using rudder in close quarters. You definitely have to keep on top of where the rudders are to avoid unexpected results. Twins with prop tunnels are more likely to need rudder use, as the tunnels significantly reduce prop walk.

Honestly, the biggest thing anyone ever told me that helped when maneuvering any boat (single or twin) is this: "You're not trying to force the boat to do something now. You're adding inputs to adjust what the boat is already doing." I see a lot of people just lean on the throttles to make the boat do something "right now" when they could get better results from a smoother, calmer technique.

The other good visual for twins is the "Shopping Cart." Push on the left hand gear, and the bow goes to the right. Pull on the left hand gear, bow points to the left (well, actually stern pulls to the right, but you get the idea)."

Barring adverse wind or current, backing away from a side tie is easiest. Using shopping cart nomenclature, if dock is on starboard side, briefly "push" on the left gear to initiate the turning momentum; then go to neutral and immediately "Pull" on the right gear which, in addition to shopping cart off-center pull, also engages prop-walk to pull the stern away from the dock.

Peter

 

[jimdavi]

Really good thread, and some great wisdom. Although I have a single, as long as there would be room to work on a twin, I’m indifferent.

If I was going to be very remote for extended times, I’d carry more spares.

I’ve noticed lots of issues show some signs before getting significant and staying on top of everything, along with strict with maintenance is very helpful.

I’m happy with my choice for our type of cruising.

 

[Cold Duck]

How do you figure that one?

I can't cite all the statistical analysis anymore but I can give a counterintuitive example of a similar situation. During WWII, a Corsair fighter squadron in the So Pacific wanted to improve their combat readiness. I can't remember the real numbers so I will just use numbers for illustration. Let's say at any given time 50% of the squadron was combat ready,15% were down for regular scheduled maintenance and 35% were down for unscheduled maintenance. The logical move would be to do more scheduled maintenance to improve the unscheduled maintenance numbers thus putting more planes online. But after analysis, it turns out most unscheduled maintenance occurred shortly after scheduled maintenance. When opening up a plane for inspection, it's easy to bend a this, pull a that, break or forget to put back a this. Today, commercial aircraft must go thru a maintenance cycle every 100 hours. Let's use that for example here. What they tried was lengthening the scheduled maintenance from 100 hours to 120hours. This put fewer planes at any time under scheduled maintenance and reduced the number of unscheduled maintenance over time thus putting something like 65% of the squadron online for combat vs 50%, simply by doing LESS maintenance! Going back to twins, statistically your maintenance will not just double when you double your engines and your MTBF (mean time between failure) will not go in half, but will actually increase. Many factors. I use to do all the numbers but getting old, now I just know the results LOL