1 vs 2 diesels, insights please..

[SteveK]

Love the protection our setup provides

Curious if it came that way. Looks like it would keep trap lines at bay too.

 

[Simi 60]

Curious if it came that way. Looks like it would keep trap lines at bay too.

She came with it.
Most trawlers (working) seem to
Info below on advantages, claimed better speed, bollard pull and fuel economy at lower speeds.

The Propeller Pages - Nozzles

 

[SteveK]

She came with it.
Most trawlers (working) seem to
Info below on advantages, claimed better speed, bollard pull and fuel economy at lower speeds.

The Propeller Pages - Nozzles

interesting all around info.

 

[xxlcajun]

Chiming in as a rookie to the TF site but a veteran of boating and working offshore and in hazardous marine environments. When an engine fails and you are in a storm, in a narrow channel with busy traffic, coming inland via the breakers or dikes, or the wind or current is moving you towards imminent danger, you will be calling on your God, be he Jesus or Poseidon, you will at that moment wish you had a second engine.

A sales guy kept trying to push me towards buying a single engine trawler that had a bow thruster, and I’m just as persistent “ How in the hell is that bow thruster going to get me home”?

 

[Simi 60]

Chiming in as a rookie to the TF site but a veteran of boating and working offshore and in hazardous marine environments.

Best not get a job on a working trawler or a ship that travels the globe.
Most run singles.

 

[Mako]

When an engine fails and you are in a storm, in a narrow channel with busy traffic, coming inland via the breakers or dikes, or the wind or current is moving you towards imminent danger, you will be calling on your God, be he Jesus or Poseidon, you will at that moment wish you had a second engine.

It's funny how my engine always fails when I'm entering an inlet or caught in big scary waves of there's a freighter coming my way. Just like in the movies

 

[Fletcher500]

Chiming in as a rookie to the TF site but a veteran of boating and working offshore and in hazardous marine environments. When an engine fails and you are in a storm, in a narrow channel with busy traffic, coming inland via the breakers or dikes, or the wind or current is moving you towards imminent danger, you will be calling on your God, be he Jesus or Poseidon, you will at that moment wish you had a second engine.

A sales guy kept trying to push me towards buying a single engine trawler that had a bow thruster, and I’m just as persistent “ How in the hell is that bow thruster going to get me home”?

It’s a personal decision regarding 1 or 2 and advantages to both. I am currently in Ventura Harbor which has a large contingent of squid boats. Many come down from AK for the season here. They range from about 40 to 80 ft and I always enjoy walking the docks and talking to them when I am here. EVERY single one of them, is a single screw.

 

[ksanders]

My opinion is different.

Do not choose one or two engines.

Choose your boat based on the mission you want to accomplish.

The engine choice becomes apparent.

For example... if you want to cruise areas with shallow water, you might look at the draft of many single engine late model boats. Is their draft comfortable for the areas you want to cruise?

Are you planning on fighting currents??? Well, a twin engine boat comes to mind with the increased horsepower they generally provide.

Again, mission determines the boat and the boat will have the engines it has.

 

[SteveK]

It’s a personal decision regarding 1 or 2 and advantages to both. I am currently in Ventura Harbor which has a large contingent of squid boats. Many come down from AK for the season here. They range from about 40 to 80 ft and I always enjoy walking the docks and talking to them when I am here. EVERY single one of them, is a single screw.

Unfair comparison.
Next time ask them about engine problems. I will guess each is well maintained, used often and the crew can make underway repairs. They probably replace items before the long trip that many pleasure cruiser waits to fail.

 

[Mako]

Unfair comparison.
Next time ask them about engine problems. I will guess each is well maintained, used often and the crew can make underway repairs. They probably replace items before the long trip that many pleasure cruiser waits to fail.

True enough, but I'd say it is an absolutely fair comparison, and every boat owner who plans remote cruising should have those same capabilities and spares onboard.

 

[Fletcher500]

Unfair comparison.
Next time ask them about engine problems. I will guess each is well maintained, used often and the crew can make underway repairs. They probably replace items before the long trip that many pleasure cruiser waits to fail.

Talked to them yesterday. JD, 600HP.

Maintenance (preventative), spares, and making repairs is part of successful cruising; single or twins.

People can make their own choice and it really doesn't matter to me what they like. Anyway, its often the boat that chooses us based on the layout, size, etc.

 

[xxlcajun]

Best not get a job on a working trawler or a ship that travels the globe.
Most run singles.

Well since those vessels mentioned above have full time engine room crew to keep her going, and engine(s) that have the capability to run on half the cylinders while work is being performed on the other half. I guess I will be relegated to sending the wife down below to breath live back into the blasted beast as we drift towards Scylla or worse Charybdis

 

[Bendit]

Best not get a job on a working trawler or a ship that travels the globe.
Most run singles.

Well since those vessels mentioned above have full time engine room crew to keep her going, and engine(s) that have the capability to run on half the cylinders while work is being performed on the other half. I guess I will be relegated to sending the wife down below to breath live back into the blasted beast as we drift towards Scylla or worse Charybdis

We’ve had a single for the last 19 years. Had one failure - starter motor solenoid. We were safely at anchor so wasn’t a dire situation but had to get towed home.
Pioneer is an ex commercial vessel with a commercially rated Cat 3406, full length keel and fully protected prop and rudder.
Obviously this sort of boat is not for everyone but it has proven very reliable and, importantly nowadays, fuel efficient.
We had twins in three vessels prior and the big single configuration gives much lower operating costs.

 

[Lepke]

Cargo ships have a single engine because it's cheaper to install a single. But it's a calculated risk, hoping they don't need two. A cargo ships' life is short, about 25 years. See the scrap report.

Ships carry many spares including pistons, sleeves, rods, etc. And if a cylinder has a failure, the rod is disconnected, the piston pushed to the top of the cylinder, the rod tied out of the way of the crank, and the engine restarted. It gets replaced in the next port. Ships centrifuge their oil so it's cleaner than what you're running. And also take better care of their fuel compared to yachts.

 

[Kapodisn]

Great post and many intriguing thoughts, end of the day, either option is the correct answer. How you plan on using your boat and why you are buying it should be the driving force behind your decision. With a side question on the bad fuel part, it doesn't matter how many engines you have, if the fuel is bad, all engines can be lost, including get me homes (unless hydraulic).

My thought process comes in the form of Cost, and not just money. Everything comes at a cost. Cost can be the peace of mind, money, or risk.

Personally, I have a hard time with single engines and a wing get me home engine. You mean to tell me you want me to rely on a small engine that gets turned on once in a while with a prop and a shaft that has been in the water with lack of use, and you want me to rely on that option to get me out of a bad spot? I am not comfortable with that. Especially most wing engines give you what 3 knots? Will that be enough to get you through an inlet or turn you around in a bad storm? Plus, you still have an elevated upkeep cost for the cost of keeping the wing engine in great condition, again even if you do turn it on or conduct maintenance. Cost is peace of mind and Risk.

If I go single engine, I will go with a hydraulic same shaft get me home that runs from my gen set, and depending on my Genset I can get 5 to 6 knots. Again, unless I lose my prop then there is that. Again...Cost is a risk.

A single-engine is a lower operating cost, not only less fuel but less upkeep and maintenance. That is a pretty good blinder for all of us, cause at the end of the day we think about cruising and relaxing on our boats, so we want to fund that rather than fund something that might happen once or twice during the lifetime of our boating experience. Cost is Risk

The multi-engine option comes with added cost, but better peace of mind. The operating budget is the balance, yes the multi-engine is worth the cost, but is the cost going to keep you from cruising and enjoying the boat? Cost is Money and peace of mind (positive and negative mindset).

For me, I would rather go for the multi-engine, added maneuverability, and added peace of mind when I do my Bahamas run or farther.

It is in the same category as Radar, no one wants a radar unless you get caught in fog or are forced to move at night without it. The same thing with the multi-engine, no one wants the second engine until you want to cross a large barrier of water with no sight of land.

If you want to go the distance you want the second engine to take you the distance. Plus, if your heart desires to take you somewhere but your thought process is your single engine, then a multi helps you with your travel destination list, again Balancing, cost and risk.

What is it worth to you?

 

[Circumnavigator]

The fallacy I see in Kapodisn's argument above is the assumption a complete propulsion failure is more likely with one engine than with two. I strenuously disagree. Unless the twin screws are mounted on heavy struts with skegs beneath them -- something I've seen only a very few times -- it is far more likely that you will loose propulsion due to damage to both shafts than to an engine failure. Log or grounding damage is much more common than a diesel engine failure assuming you have proper triple fuel filtration.


I also disagree that twins are more maneuverable, but that's a much more subjective decision.



My peace of mind comes from having much better protection underwater.


Jim

 

[Comodave]

It depends on the boat. Our last boat, a President 41, had twin engines. We were going up the Hudson early in the spring in 2016 and hit submerged objects, I assume trees since there were a lot of them floating in the river, about 12+ times. Some were hard enough to make the whole boat shudder. I thought well we have spare props so we can always change them out. When we got home and had the boat hauled there was absolutely no damage to the props. Now out Formula would sustain severe damage to the props in the same situation because it doesn’t have a keel. So I don’t buy that all twin engine bolts are likely to have prop damage if you strike something.

 

[Kapodisn]

The fallacy I see in Kapodisn's argument above is the assumption a complete propulsion failure is more likely with one engine than with two. I strenuously disagree. Unless the twin screws are mounted on heavy struts with skegs beneath them -- something I've seen only a very few times -- it is far more likely that you will loose propulsion due to damage to both shafts than to an engine failure. Log or grounding damage is much more common than a diesel engine failure assuming you have proper triple fuel filtration.


I also disagree that twins are more maneuverable, but that's a much more subjective decision.



My peace of mind comes from having much better protection underwater.


Jim

I am under no illusion that a twin cannot lose an engine. The thought is that when you do lose one engine you have a second engine to get home rather than a get-me-home setup.

With keel designs to "enclose" the shaft and screw on a single engine are more protective from that point of view. If you have a hull that has that setup.

For a multi-engine setup, you can lose an engine, there is no fallacy about that. Sorry, you took it that way.

 

[rslifkin]

It depends on the boat. Our last boat, a President 41, had twin engines. We were going up the Hudson early in the spring in 2016 and hit submerged objects, I assume trees since there were a lot of them floating in the river, about 12+ times. Some were hard enough to make the whole boat shudder. I thought well we have spare props so we can always change them out. When we got home and had the boat hauled there was absolutely no damage to the props. Now out Formula would sustain severe damage to the props in the same situation because it doesn’t have a keel. So I don’t buy that all twin engine bolts are likely to have prop damage if you strike something.

I've had similar experience. I've had quite a few submerged debris hits on my boat. One of them sounded like it just grazed a prop, but did no damage. The rest have all bounced off the keel and come up behind the props (if it ever came up). My props hang about 5 inches below the keel, but the slight downward angle of the keel, etc. has generally been enough to kick debris down far enough to clear the props.


In a grounding it's a different story. If it's a steeply sloped bottom I'd hit keel first, but if it's a pretty gentle slope or a piece of debris sticking up in shallow water, then there's a good chance I'd hit one or both props.

 

[Mako]

Regarding to the statement:

"If I go single engine, I will go with a hydraulic same shaft get me home that runs from my gen set, and depending on my Genset I can get 5 to 6 knots."

What you don't factor in is that the genset will now need to be sized similar to a get-me-home side engine. So a 40ft cruiser may need a 40kW generator. There's no way to load that up properly, weekly, with electric demand on a boat that size. So now you need to run the boat for a few hours on your hydraulic drive - so out comes the big fat oily greasy chain to be connected. This is also assuming that you have switched out your marine gear for one which will run without hydraulic pressure. Unless you make connections for that off of the genset as well. It is a lot more complicated than you think.

Your typical 5kW Kohler may push you along at 1 knot... downwind.

For the record, I'm a fan of singles with the above setup, but nothing is simple or zero maintenance. If you want as simple as possible, then have a single, no genset, and just take care of your engine and fuel meticulously. Buy a SeaTow membership.

 

[Kapodisn]

Your typical 5kW Kohler may push you along at 1 knot... downwind.

,
.....Buy a SeaTow membership.[/QUOTE]

Hydraulic setups have come a long way, and again if you have room on your shaft line to add one at least.

Also, the SeaTow membership is probably the best $200 annual investment there is.

 

[catalinajack]

This twin vs single discussion is, and always will be, endless and with no clear "winner". Here is this boater's experience.

I have a DeFever 44 with Lehman 120s, but no matter the engine. Twice, once on each side at different times, I suffered a failure of the DriveSaver coupling. Both times occurred at very inopportune times. Having a second engine saved me big time, both times. The second time was at Cayo Costa, 45 miles from our destination of Fort Myers on a Christmas Eve day. I needed a tow off a bar (another story, irrelevant here). Towboat US sent a boat that got us free. Fine, but that boat had insufficient power (not even close) for a 45-mile tow. As it was, we got to Fort Myers in the dark after a very slow (wind and opposing current) on one engine. Had we had only one engine, we would have been stuck at Cayo Costa for two days. And then there would have been the question of where to be towed for repairs. Nope, it's twins for this guy, every day, every boat.

By the way, my boat no longer has DriveSavers.

 

[Kapodisn]

I suffered a failure of the DriveSaver coupling.

Nope, it's twins for this guy, every day, every boat.

Thanks for sharing. For me my personal choice, I am with you, twins for every boat.

Question. On the DriveSaver coupling, if you have an extra on hand would that be able to resolve the situation you encountered?

 

[mvweebles]

Your typical 5kW Kohler may push you along at 1 knot... downwind.

,
.....Buy a SeaTow membership.

Hydraulic setups have come a long way, and again if you have room on your shaft line to add one at least.

Also, the SeaTow membership is probably the best $200 annual investment there is.[/QUOTE]

Can't speak for Kohler, but I believe a PTO is not available on Northern Lights generators under 9kw. Several Willard 40's were equipped with electric motor get-home motors. It was paired with a 3-phase 12kw generator which was difficult to source and expensive. Most get-home setups were moth-balled.

Peter

 

[Delfin]

Most single screw boats protect the wheel behind a keel. With twins, they are generally more exposed, so damage to one screw is certainly easier to see happen. What this means is that those with twins love them because they may have experienced damage to an exposed screw so are grateful for the other. Single screw folks don't have that experience since their prop is better protected. That, plus the 1/2 maintenance hassle may explain why most commercial vessels in the size we putt around in are singles.

 

[catalinajack]

Thanks for sharing. For me my personal choice, I am with you, twins for every boat.

Question. On the DriveSaver coupling, if you have an extra on hand would that be able to resolve the situation you encountered?

Yes, an extra on hand would have been helpful but the fact would have remained that I would continue to have a weak link in the drive line. After my two experiences with them, I will never have them in any boat I own. I replaced them with spacers supplied by Spurs Marine, the folks who make line cutters.

 

[catalinajack]

Most single screw boats protect the wheel behind a keel. With twins, they are generally more exposed, so damage to one screw is certainly easier to see happen. What this means is that those with twins love them because they may have experienced damage to an exposed screw so are grateful for the other. Single screw folks don't have that experience since their prop is better protected. That, plus the 1/2 maintenance hassle may explain why most commercial vessels in the size we putt around in are singles.

Yup, you are 100% correct but I still rather twins. And not all boats with twins have the same level of risk of damage. My boat, a DeFever 44, has a full-length keel such that the leading edge of the props are about four inches above the keel. While not as protected as a single, the risk is not nearly that of the naked running gear found on many boats.

 

[rslifkin]

There's definitely no reason twins have to have exposed running gear. Many do, but not all. Look at the underbody of one of the Great Harbor trawlers, for example. Twins, but with big, beefy skegs protecting the props and rudders. If you're looking at designs like that, single vs twin mostly comes to things like what fits better in the boat, what are the most suitable engines for each, whether the twins give a reduced draft, etc.

 

[TBill36]

I haven't read the entire thread, so someone may have mentioned this. Electronically controlled deisels have an additional factor that can cause them to be inoperable. If you fully understand and carry spares for all the electonic components then you may be equal with a mechanial engine as far as reliabilty, but I doubt it.

I've had friends with newer electronically controlled engines that have had to deal with electrical issues. One wouldn't run, and one would start by itself with no one around.

My old engines take a battery to turn it off unless I go to the engine room and push down on the fuel solenoid plunger. I think I could withstand a lightning strike and the engines would still be running - although I might be dead.

 

[mvweebles]

Most single screw boats protect the wheel behind a keel. With twins, they are generally more exposed, so damage to one screw is certainly easier to see happen. What this means is that those with twins love them because they may have experienced damage to an exposed screw so are grateful for the other. Single screw folks don't have that experience since their prop is better protected. That, plus the 1/2 maintenance hassle may explain why most commercial vessels in the size we putt around in are singles.

While I understand the sentiment here - that twin owners have more experience with engine failure due to prop exposure - the bulk of the assertions are bunk. There simply is no denying that twins offer some level of redundancy - what is debatable is how much risk is mitigated and what are the tradeoffs. That can be a really personal calculus, it is for me.

That said, there are twins with fairly well protected props but not many (DF44 and the Great Harbors mentioned above are pretty good, but standouts because of the rarity). These days, most have centerline skeg as a lowest extremity but that offers only modest protection compared to a full keel such as my Willard (which in all fairness, is also fairly rare - my boat can absorb an incredibly hard grounding unscathed). The growing popularity of outboards on distance boats is the epitome of exposed running gear.

After dozens of these single vs twin threads, I have come to the conclusion that some people are single people, some are twins. Their mind is mostly made up and they each have their reasons based on what they prioritize, prior experience, and their use-case. For example, I didn't worry much about skinny water when on the Pacific Coast. Florida is a much, much different matter. People in the PNW see logs all the time which is uncommon elsewhere.

I think every response to a thread like this should begin with "I chose <twins>/<single> because xxxx reasons that are impoetant to me.....".

Peter