The Great Debate

[Open-d]

One working engine is all anyone needs. That is why I have twins

That is soooo funny, and true!

 

[Open-d]

Suggest you forego the general chat style internet and use some shoe leather. On this vessel there is no choice, twin DDs. Go to boatdiesel and peruse the thousands of posting on DDs for your internet answer. Remembering that prior use and maintenance is the key on a decades old vessel.

The question isn't about DDs, per se. It is about sufficient HP? I went to boat diesel, and they said to come here!!!

 

[syjos]

One working engine is all anyone needs. That is why I have twins

That's a great comment.

 

[Bryant]

single vs twin

I've been away from the forum for some time, and wonder if the debate between between single and twins has been decided once-and-for-all yet, and if so, what is the decision? I am still a bit on the fence, but leaning more towards a single than before.

I'll give you my thoughts and why.

First, if purchase price was no object and then money was no object concerning slip fees, ins, maintenance, upkeep, repairs etc and I lived where diesel mechanics, electricians, plumbers, hvac, carpenters etc were only a phone call away then I'd buy the latest model, largest, twin engined trawler with a stand up, walk around engine room that I could find. If this situation applies to you, then that's my advice.

Having said that, I'm not in that position. I need a boat that's large enough to do what I want to do with the amenities that I need that I can own without a mortgage. This is my GB 36. In my boat I required a single engine. I can walk (knee crawl) completely around it and I can easily reach all other systems in the engine room. I have my generator, engine and transmission professionally maintained (for reasons I can enumerate later if you are interested) and that runs $1000/year. When the boat is pulled I only have one shaft, packing gland and cutless bearing to deal with. I burn 2.5 gals/hour with the generator running when I'm underway. Additionally, my keel protects my screw, shaft and prop. If I ever need to replace or rebuild I only have the cost of one engine and or transmission.

If I had twins then the original purchase price would probably have been higher and all other costs are doubled. All other maintenance requirements are doubled. All other headaches are doubled. The twin engine guys maintain that there is more reliability in two engines than one. This is occasionally true but the fact is that most problems associated with engine trouble on well maintained engines is fuel related. Key here is "well maintained" . If you have a fuel problem and lose one engine, the other one is not far behind. There is a saying in aviation that goes "The second engine just gets you to the scene of the crash that much more quickly". That's a humorous and simplistic way of dismissing the need for more than one engine.

Maneuvering a boat is infinitely easier with twins and or bow/stern thrusters. I have neither and I frequently have people comment that it must be nice to have twins or thrusters after watching me back into my slip. When I tell them I have only one engine and no thrusters, they are amazed. Point is, with practice, you can learn to maneuver your boat quite well with only one engine.

If you are going to do long distance, blue water cruising or you have remote destinations in mind I might consider two engines but for my use (and most people's) one engine is sufficient and much less expensive and less trouble all the way around.

Hopefully, I've given you some food for thought. Read over what the twin engine crowd has to say and then decide what is important and makes sense for you.

Good luck and have fun hunting.

 

[Bryant]

LOL! Now that's funny!
Talking about LaBomba's picture.

 

[Bryant]

single vs twin

Since you want to throw bombs, you might as well go full stroke and re-ignite the best dinghy question too? I don't have one anymore; so no dog in that hunt.

Why stop there? Let's talk anchors.

 

[Bryant]

single vs twin

Damn, I go away for a couple of weeks and I miss all the fun, well here goes. I have literally thousands upon thousands of miles racked up on commercial boats with single engines. I've owned quite few also and while anyone should make their own choice I prefer a single. The reasons are buried throughout the numerous posts on this subject so need not be repeated by me. There's my vote and I hope I offended no one.

Wow, Pitcairn Island? Now that peeked my interest. Currently finishing my fourth book on The Bounty.

 

[Bryant]

single vs twin

Are those spares along the lines of belts and hoses, or more significant parts such as impellers, bearings etc.?

All the above. If possible, have a spare for everything on the motor that is addressed during annual maintenance and then a spare of every add on as well.

 

[Bryant]

single vs twin

The idea of having to change the oil in a fuel pump, with the opportunity of losing or stripping a plug or the housing is more-than-enough to keep me away from the FL120 engines. I am not a mechanic. I am more "operations" and less "engineering", even less maintenance and certainly very little "repair". I have very problematical hands and such activities while adrift at the mercy of the seaway is something to be avoided to me.

Thank you for you carefully considered response.

I've been reading this entire thread out of interest and have made a couple of contributions. When I read this post of yours I almost fell out of my chair. Single vs twin conversations are almost irrelevant to your situation.
Believe me, you are not ready for, nor should you even consider making a passage from Hawaii to the South Seas at this time. This is not meant as an insult or a dig, just good advice. There are many good marine diesel and boat systems maintenance courses out there. I strongly suggest that you attend one if only to learn how to change oil, filters, bleed the lines, change belts/hoses etc. You are seriously putting your life and the lives of those with you at risk on a cruise of the type you are considering without at least a basic ability to address even minor engineering problems.
For the record, I wouldn't attempt that crossing myself so I'm not preaching. I'm just strongly suggesting you obtain some maintenance skills before setting out.

 

[Open-d]

Thank you for that reply.

 

[Open-d]

I have some skills, but not repair-type. I considered one of those classes already, and will get some sort of basic training. I also may scale back my plans to cruising the med and west coast of europe. We are looking at retiring in Portugal. In any case, I won't start ang long-distance trip without first gaining and honing skills.

More importantly, i want this thread to be about engines and the single vs twins specifically not about me. We'll save that for later.

Thank you for your input.

 

[BandB]

I have some skills, but not repair-type. I considered one of those classes already, and will get some sort of basic training. I also may scale back my plans to cruising the med and west coast of europe. We are looking at retiring in Portugal. In any case, I won't start ang long-distance trip without first gaining and honing skills.

More importantly, i want this thread to be about engines and the single vs twins specifically not about me. We'll save that for later.

Thank you for your input.

But it is all interwoven. The engine choices include cruising grounds, type of boat, and the skills and experience of the owner or crew.

For us, it's simple, twins. But it's twins for reasons not applicable to most here. We want speeds that require twins. We just finalized an order for a boat today with triples.

If we were talking gas engines I'd encourage twins more than on diesel based on dependability and repair ability at sea. If outboards even more on twins or triples because non-fuel related failures are more common. I'll toss one more out and that is IPS. There's definitely a higher probability of drive failure on IPS than on traditional inboard so I'd be even stronger on twin.

For those seeking simplicity and not interested in any additional speed, then single makes a lot of sense. However, more so, certain builders have build very good dependable boats using singles. If going for small to medium sized KK or Nordhavn, they just make sense. Outer Reef is going to always be twins.

One opinion I've formed is do what the builder typically does and does well. If I found the boat I liked, I wouldn't be discouraged from it by either single or twins. I'm more concerned with how it performs and with both what redundancy it has. I haven't and never will declare twins or single to be superior because neither is universally better.

Single is fine. For ocean crossing need a good get home option. But don't have to have twins. That said, I'll never personal have a single.

 

[Airstream345]

Open-d, our KK54 displaces 67800# and a single 210 hp CAT moves her along just fine.

When I was looking hard at Hatteras 58 LRCs I tended toward the 6-71 powered boats as they were reported to perform better in head seas than the 4-71s.

PS - the Hatteras LRCs are another model you may consider. Tanks. Lot's of fuel, stand up engine rooms, etc.

 

[syjos]

I'll give you my thoughts and why.

First, if purchase price was no object and then money was no object concerning slip fees, ins, maintenance, upkeep, repairs etc and I lived where diesel mechanics, electricians, plumbers, hvac, carpenters etc were only a phone call away then I'd buy the latest model, largest, twin engined trawler with a stand up, walk around engine room that I could find. If this situation applies to you, then that's my advice.

Having said that, I'm not in that position. I need a boat that's large enough to do what I want to do with the amenities that I need that I can own without a mortgage. This is my GB 36. In my boat I required a single engine. I can walk (knee crawl) completely around it and I can easily reach all other systems in the engine room. I have my generator, engine and transmission professionally maintained (for reasons I can enumerate later if you are interested) and that runs $1000/year. When the boat is pulled I only have one shaft, packing gland and cutless bearing to deal with. I burn 2.5 gals/hour with the generator running when I'm underway. Additionally, my keel protects my screw, shaft and prop. If I ever need to replace or rebuild I only have the cost of one engine and or transmission.

If I had twins then the original purchase price would probably have been higher and all other costs are doubled. All other maintenance requirements are doubled. All other headaches are doubled. The twin engine guys maintain that there is more reliability in two engines than one. This is occasionally true but the fact is that most problems associated with engine trouble on well maintained engines is fuel related. Key here is "well maintained" . If you have a fuel problem and lose one engine, the other one is not far behind. There is a saying in aviation that goes "The second engine just gets you to the scene of the crash that much more quickly". That's a humorous and simplistic way of dismissing the need for more than one engine.

Maneuvering a boat is infinitely easier with twins and or bow/stern thrusters. I have neither and I frequently have people comment that it must be nice to have twins or thrusters after watching me back into my slip. When I tell them I have only one engine and no thrusters, they are amazed. Point is, with practice, you can learn to maneuver your boat quite well with only one engine.

If you are going to do long distance, blue water cruising or you have remote destinations in mind I might consider two engines but for my use (and most people's) one engine is sufficient and much less expensive and less trouble all the way around.

Hopefully, I've given you some food for thought. Read over what the twin engine crowd has to say and then decide what is important and makes sense for you.

Good luck and have fun hunting.

I agree 100%

A very thoughtful post.

 

[syjos]

Wow, Pitcairn Island? Now that peeked my interest. Currently finishing my fourth book on The Bounty.

I spent several months last year researching everything available about the Bounty. The most fascinating was the history about the Marlon Brando movie's ship.

We are probably drifting too far from the thread. Probably should start a new thread.

 

[rslifkin]

If we were talking gas engines I'd encourage twins more than on diesel based on dependability and repair ability at sea. If outboards even more on twins or triples because non-fuel related failures are more common. I'll toss one more out and that is IPS. There's definitely a higher probability of drive failure on IPS than on traditional inboard so I'd be even stronger on twin.

With outboards or exotic drive setups, I agree. But for gas inboards, I can't really say a decently engineered installation is really less reliable than diesels, although the lifespan is likely to be shorter. For the most part, as long as periodic ignition system maintenance is done, my carb-ed with electronic ignition gassers are very much like diesels in the sense that they "just work" without fussing or needing any kind of tinkering, etc.

 

[Open-d]

Open-d, our KK54 displaces 67800# and a single 210 hp CAT moves her along just fine.

When I was looking hard at Hatteras 58 LRCs I tended toward the 6-71 powered boats as they were reported to perform better in head seas than the 4-71s.

PS - the Hatteras LRCs are another model you may consider. Tanks. Lot's of fuel, stand up engine rooms, etc.

Yes I discussed that in an earlier post on this thread. The 65' looks mighty appealing. We'll have to see how my portfolio grows over the next 6 months. For that vessel, I would definitely opt for the 6 vs the 4.

 

[Fletcher500]

Yes I discussed that in an earlier post on this thread. The 65' looks mighty appealing. We'll have to see how my portfolio grows over the next 6 months. For that vessel, I would definitely opt for the 6 vs the 4.

P/E valuations are rich, Fed will eventually have to tighten despite the tweets, lots of other economic factors as well. This last 10 year cycle is long in the tooth. Personally, I wouldn’t put a lot of faith in portfolio growth over the next few years, but we shall see. My crystal has not been correct lately.

 

[Open-d]

P/E valuations are rich, Fed will eventually have to tighten despite the tweets, lots of other economic factors as well. This last 10 year cycle is long in the tooth. Personally, I wouldn’t put a lot of faith in portfolio growth over the next few years, but we shall see. My crystal has not been correct lately.

If President Trump is re-elected, I have no substantial fears of a stock-market meltdown, but one never knows and must be prepared to go to cash when necessary.. I've been doing well with a few tech stocks, most-notably Nvidia. Just keeps on marching upwards and onwards.

However, this begs the question, Single stock or Twins?

 

[MYTraveler]

So depending on hull design, etc. it might be possible to reduce draft by a couple of inches with twins.

Good point -- smaller props reduce draft. But also, if hull bottom isn't flat, another few inches may be achieved by moving the props off center.

 

[BandB]

Wifey B: Why do you just ask about single or twins. What about triples or quads or quints.

 

[Open-d]

Wifey B: Why do you just ask about single or twins. What about triples or quads or quints.

Who is Wifey B?

 

[BandB]

Who is Wifey B?

Wifey B: Me, me, it's me, it's me, it's Wifey B: Sounds like Ernest T.

BandB

Hubby B and Wifey B

Hubby B unless indicated as Wifey B:

We share the account and both post. It's a system designed to keep you confused. Hubby B is on the phone or he'd join in. We're about to go to dinner. People sure eat late here. Most of the restaurants don't open til 7:30, 8:00 or 8:30.

 

[Open-d]

Wifey B: Me, me, it's me, it's me, it's Wifey B: Sounds like Ernest T.

BandB

Hubby B and Wifey B

Hubby B unless indicated as Wifey B:

We share the account and both post. It's a system designed to keep you confused. Hubby B is on the phone or he'd join in. We're about to go to dinner. People sure eat late here. Most of the restaurants don't open til 7:30, 8:00 or 8:30.

Your system worked as designed!!

 

[FF]

Single vs twin the arguments go on forever.

My take is the danger of Twins is wiping out the props , shafting and rudder underway. A Sea Land box or sand bar or.... ,

A Single could (maybe 1 -10,000 could fail mechanically) .

The solution is OTS and available new or used for about 75 years .

The military and others use twin engines coupled to a transmission with a single shaft.

The shaft is very robust to handle the loads and if center line mounted would be able to take the ground like any good single.

Either or both engines can operate ,as desired, they can even be different sizes so one could operate a de fueler in coastal areas or an economy heavily loaded small engine for offshore passages.

I would have a 3-71 and a 6-71 package as there would be common parts to share if it came to that.

Totally different fuel systems would add to reliability.

The only downside is the tranny is heavy .And both engines have to be shut down to re engage an off line engine.

But it answers the single or twin question,

BOTH!

 

[catalinajack]

I have twins. I maintain them as well as any single engine owner.

[emoji1][emoji1][emoji1][emoji1]
So true!
Now duck

 

[Nomad Willy]

FF wrote;
“The only downside is the tranny is heavy”
Well it was made by the people (GM) that made the two stroke “Detroit” diesel engines and despite the fact that two stroke engines were/are universally lightweight the GM Detroit diesels were monsters so one would expect the trans to also be overbuilt.

Would you know do the pistons on a 2-71 (or 2-53) rise and fall together of alternately?

 

[rslifkin]

My take is the danger of Twins is wiping out the props , shafting and rudder underway. A Sea Land box or sand bar or....

That one is down to hull design. If you can live with some extra drag, twins can be protected like a single. The ultimate would be twin skegs to protect the props / rudders. The next best is to do like a Grand Banks and make the keel extend below the props. That won't protect you from debris in the water, but it'll typically keep you from hitting props-first in a grounding.

I'll admit that prop to bottom contact is one of my biggest concerns in shallow water. In my case, the props are about 5" below the keel, so they're the lowest point on the boat. The rudders don't extend quite all the way down, so it's unlikely that you'd damage a rudder without having completely destroyed the prop in front of it.

And that's why with a draft of 3'8" (fully loaded in fresh water), my eyes start to get pretty big once the depth gets under 6 feet. Once it gets down to 5, it's time to and carefully go back the way we came.

 

[Open-d]

FF wrote;
“The only downside is the tranny is heavy”
Well it was made by the people (GM) that made the two stroke “Detroit” diesel engines and despite the fact that two stroke engines were/are universally lightweight the GM Detroit diesels were monsters so one would expect the trans to also be overbuilt.

Would you know do the pistons on a 2-71 (or 2-53) rise and fall together of alternately?

I am pretty sure they don't rise and fall together, or it would soon vibrate itself to death.

 

[Open-d]

Single vs twin the arguments go on forever.

My take is the danger of Twins is wiping out the props , shafting and rudder underway. A Sea Land box or sand bar or.... ,

A Single could (maybe 1 -10,000 could fail mechanically) .

The solution is OTS and available new or used for about 75 years .

The military and others use twin engines coupled to a transmission with a single shaft.

The shaft is very robust to handle the loads and if center line mounted would be able to take the ground like any good single.

Either or both engines can operate ,as desired, they can even be different sizes so one could operate a de fueler in coastal areas or an economy heavily loaded small engine for offshore passages.

I would have a 3-71 and a 6-71 package as there would be common parts to share if it came to that.

Totally different fuel systems would add to reliability.

The only downside is the tranny is heavy .And both engines have to be shut down to re engage an off line engine.

But it answers the single or twin question,

BOTH!

We were transiting from west coast to Hawaii in a twin-screw vessel, when one of the shaft bearings started overheating. In order to prevent more damage to the bearing, we shut down that engine and proceeded under 1.

Point is that it is more than JUST the engine that can fail. If we were a single-screw vessel, we would have to have slowed considerably, and perhaps lost the bearing anyway, necessitating a tow.

I have to agree that the protections afforded a single-screw by the keel is a significant plus for a single screw config.