Single vs Twin: It's Baaaaack!

[sunchaser]

ksanders said:
"Use a Naturally Aspirated engine Do they make these after 2012 anymore other than remans? And give up the improved emissions performance and nmpg on a new engine?
Use an engine with no belts. Alternator duties performed how?
Easier access with a single" Not on all singles, and Marin can service his twins on his GB 36. There are lots of easy access twins out there, not all are Bayliiner cramped.

 

[SomeSailor]

Much lower MTTR is acheived through easier access to the engine for repairs. This makes repairs much faster when a failure occures.

I'd have to disagree there Kevin. I can sit upright on either side of either of my engines. I can get a wrench on everything very easily. Changing the injector oil on my stbd motor can get a little tight.

I really can't see how anyone can say a single engine is reliable, and yet a pair of those single engines would be LESS reliable.

At the very heart of every reliability engineering study I've seen is the degree of redundancy. Build a fault tree diagram for a boat's propulsion system and you'll find very few (if any) examples that could bring down a twin that would not bring down a single.

My fuel system is an example. I have dual tanks, two independent and redundant fuel filtration system with redundant lift pumps. Either tank can be used to fuel either engine (through redundant filtration).

This system is truly redundant. I would even like to have a day tank like Marin has to further increase my reliability model.

Are they worth the money? I dunno. I guess that needs to be seen at sale. I've never heard anyone walk on the boat and look below and say... "Oh bummer... I see you're stuck with two engines."

 

[ksanders]

ksanders said:
"Use a Naturally Aspirated engine Do they make these after 2012 anymore other than remans? And give up the improved emissions performance and nmpg on a new engine?
Use an engine with no belts. Alternator duties performed how?
Easier access with a single" Not on all singles, and Marin can service his twins on his GB 36. There are lots of easy access twins out there, not all are Bayliiner cramped.

Here's a quote from Luggers website

Lugger's design philosophy has been it's strength from the beginning. Fresh and raw water pumps are gear-driven to eliminate belts. Most hoses and leak points have been engineered away.


To be honest I do not know is NA engines are available any more as new installs. What I do know is that something that does not exist cannot break. Using gear driven pumps removes the possibility of a belt failure causing an engine to be inoperable.

I do believe that the alternator on the lugger is still belt driven. An alternator loss will not stop an engine from running. It will stop battery charging which would require the use of your generator to keep up the batteries.

I'd have to disagree there Kevin. I can sit upright on either side of either of my engines. I can get a wrench on everything very easily. Changing the injector oil on my stbd motor can get a little tight.

"

As far as the access issue, I can get to all four sides of both of my engines. I can reach every nut, bolt, hose, etc... That said, if my engine compartment only had one engine It would be easier to move around it. That ease would result in my being able to fix it faster. Thats all I was suggesting.

 

[SomeSailor]

That said, if my engine compartment only had one engine It would be easier to move around it. That ease would result in my being able to fix it faster. Thats all I was suggesting.

I get that. I just wanted to clarify that on many old trawlers that's not the case though. I don't want people to assume that the second engine prevents maintenance or adds accessibility problems that would lead to poor maintenance or increased down time.

I don't think that would be the case with my design.

I get the cost argument, but the handling and redundancy more than offset any of that.

 

[Nomad Willy]

Belts???

What's wrong w belts Tom? Gotta change them once every several years ..... no problem. I've chose a belt driven seawater pump at repower and haven't been sorry. Belts are 7 years old. Look great and almost never need adjustment. I don't view belts as a weak link but technically most parts on an engine are.

But if one had twin engines the potential of two belts breaking that received proper maintenance is ridiculously and utterly remote.

 

[SomeSailor]

But if one had twin engines the potential of two belts breaking that received proper maintenance is ridiculously and utterly remote.

Change them on opposing cycles and you can even further reduce the chances. I can definitely see how some would see it wouldn't be worth the extra expense, especially if buying new.

But aside for the initial investment, and some additional maintenance, I'd still opt to have two. It's just a personal preference at some point.

 

[Marin]

I really can't see how anyone can say a single engine is reliable, and yet a pair of those single engines would be LESS reliable.

I think that's a really good way of stating the issue.

 

[Codger2]

I think that's a really good way of stating the issue.

I, grudgingly, agree. I will say, however, using the same logic, there must be considerably more room in the ER with a single than with "2 singles."

 

[Marin]

I, grudgingly, agree. I will say, however, using the same logic, there must be considerably more room in the ER with a single than with "2 singles."

No argument there. But depending on the size of the boat, the type of engines, and the layout of the engine room two engines does not automatically equate to inaccessible. Particularly if the engines have an in-line cylinder arrangement as opposed to a Vee.

 

[SomeSailor]

In some ways I have more room. My slip neighbor has a 45' CHB with a single. Since his motor is online the center line, he cannot move around it on each side with the same height I have in between mine. My batteries are all beneath the decking right along center line, his are off to each side. My genset is on center line as well. I have a good 48" or so between the engines. I'd have more room with a single, but not the same type of room I have now.

 

[Anode]

I don't have room for two engines. But it really doesn't matter because all I have is one.

 

[markpierce]

Why are so many, so defensive? The last person posting isn't necessarily correct nor won the argument. There is no universally correct answer.

Had a belly-laughing party last night with Perla's friends on the Coot. Stayed in-berth, so number of engines was quite irrelevant.

 

[Marin]

There is no universally correct answer.

Sure there is, Mark. If you have a power boat, you need power.

How's that?

 

[markpierce]

Sure there is, Mark. If you have a power boat, you need power.

How's that?

Marin, used no power except that shore-provided this New Year's eve.

 

[Marin]

To be honest I do not know is NA engines are available any more as new installs.

Up until a few years ago--- and perhaps still today--- Lugger offered a six-cylinder, NA inline diesel of 150 hp. IIRC it was based on a John Deere block and was a very popular engine for repowering boats originally fitted with engines like the FL120, FL135, etc.

A good friend of ours was for decades the head of the engineering department of Northern Lights/Lugger (formerly Alaska Diesel Electric), and he told us that this engine has been used in a number of Grand Banks re-powers in this area over the years.

As I've mentioned before, we have an idea on the back burner to have our boat completely overhauled up in BC in the not-too-distant future which would include a repower of the main engines and generator. At the time we put this idea together we decided to use this particular Lugger engine. Other projects keep getting in the way of this one so we have not kept up with the availability of this engine.

 

[mahal]

"Anybody thats ever experienced an engine failure was either glad they had twins, or wished they had twins."

This is the best statement I've come across in the single vs. twin debate. One would have to be silly to argue this one.

 

[markpierce]

Mahal, I'm happy for you. Wish me luck with the Coot's single. My guardian angel appreciates acknowledgment (hint, hint).

 

[markpierce]

"Anybody thats ever experienced an engine failure was either glad they had twins, or wished they had twins."

This is the best statement I've come across in the single vs. twin debate. One would have to be silly to argue this one.

And you're likely to have twice the failure rate of any single engine since having twice the number of engines.

 

[Marin]

And you're likely to have twice the failure rate of any single engine since having twice the number of engines.

I think we already proved that this in reality is not correct in this or some other thread.

 

[markpierce]

I think we already proved that this in reality is not correct in this or some other thread.

You are defying logic. If you have two engines, both will eventually fail. If I have one engine, it will eventually fail. So, you had two engines fail, and I had only one fail. I've never said or implied someone having two engines will necessarily have them both fail before someone's single engine.

 

[SomeSailor]

And you're likely to have twice the failure rate of any single engine since having twice the number of engines.

You'll have twice the failures. This is true.

You'll fail at exactly the same rate. And since they are nearly completely independent of each other, so are the failures. (and therefore highly unlikely to happen simultaneously)

 

[mahal]

And you're likely to have twice the failure rate of any single engine since having twice the number of engines.

Even if I had 5 times the failure rate of a single it still doesn't matter as I will still have the other engine to do whatever I please, be it continue with my trip or go home.

 

[Marin]

I've never said or implied someone having two engines will necessarily have them both fail before someone's single engine.

That's why I said "...in reality..."

 

[sunchaser]

Marin said:

" At the time we put this together we decided to use this particular Lugger engine. "

In looking at Luggers Current model lineup the only NA engine they offer is 40 HP. It appears JD's Current model lineup has an 80 HP NA version of the 4045.

 

[psneeld]

Even if I had 5 times the failure rate of a single it still doesn't matter as I will still have the other engine to do whatever I please, be it continue with my trip or go home.

Those of us that have singles, carry spares, know how to deal with failures and emergencies in a timely way have ecxactly the same opportunities....continue the trip or go home.

 

[Marin]

Marin said:

In looking at Luggers Current model lineup the only NA engine they offer is 40 HP. It appears JD's Current model lineup has an 80 HP NA version of the 4045.

Okay, thanks for the info. So it seems if we end up pursuing our re-engine plan it would have to be with a turbocharged engine because we'd want at least 150 hp per side if not 200 or more. Too bad.

 

[sunchaser]

Marin, a good option may be a Cummins reman 210 NA. Full warranties are available.

 

[Marin]

Marin, a good option may be a Cummins reman 210 NA. Full warranties are available.

Thanks for that info. I have filed it with the rest of the information we've been compiling about this potential project.

 

[Codger2]

Marin, a good option may be a Cummins reman 210 NA. Full warranties are available.

I had a 38' sport fisher with a pair of Cummins 210s and 2 single engine boats, both with Cummins. I've also had a 54' sport fisher with a pair of 8V92 DDECS. (760hp each) My current boat is a single & has a Cummins 330B. Now, I don't want to throw mud on anyone else's engines but I've had Cats (2 pairs of 3208s) a pair of Perkins 200s and 3 Cummins & I love the Cummins. Easy to change the belts, you can move the dip stick and oil fill if it's not in a place that suits you, etc. I've never had a problem or engine failure with the Cummins. They would be great re-mans for a lot of boats.

 

[Nomad Willy]

If an engine were to have a record of failure and that record was an accurate account the record for two engines would obviously be twice as high so a failure of one of the two would be double that of one ... duh

But after one fails the chance of the other failing is rather unlikely and it's so obvious I feel stupid saying it.

I repeat that the only reason we're having this discussion is the undeniable fact that most single engine skippers are afraid one of their engines are going to fail and leave them helpless (except for psneeld of course (who has an abundance of bailing wire and lots of confidence)) so we single engine skippers are doomed to live in fear of the lights going out and becoming helpless.

I for one know this as it happened to me this summer and I'm having lots of serious thoughts of a suitable get home. Wether I go boldly forth w/o one or not dosn't alter the fact that given enough time te engine will fail again and I'll wish I had twins again. I've wished that all along.

If you take away the redundancy factor many will still think twins are better so what does that say for those arguing against twins where the redundancy does apply.

I think it's proof that men will argue that what they have is better than what the other man has to justify where they are in the world but mainly to justify themselves.