Backup

I'm a single-engine kind of guy. Let's just take that as a given.

Many single-engine boats going offshore have a backup propulsion system. These backup systems have varying degrees of dependence on the primary systems.

How often are these backup systems used in anger? How often is a more-independent system more valuable than a less-independent one?

Ideally I'd love to see some numbers here: the main engine in such an environment fails every XX hours, the prop/shaft becomes disabled every YY hours, fuel problems that impact all boat systems occur.. That'd make it easy to quantify the value of not only backup propulsion systems in general, but the the relative value of specific types of backups.

Unfortunately I'd be real surprised if such numbers exist in a statistically significant form. And so I'll ask for anecdotal information:

If you do go out of towboat range, have you needed your backup system? What type of failure did you encounter, and what would have been the consequences of not having the backup?

Our backup engine is entirely independent, except for drawing diesel from the same two tanks. We had to use it once, almost twice.

Failure type: ruptured oil filter (bolt backed thru it (kid you not)) caused low oil alarm on main. Shut down main started backup and tied to the first dock we saw. We were in the ICW, it was 30 minutes till dark and we had no way to quickly anchor (windlass was being rebuilt). So it was very useful to have it.

Btw, the windlass had been due back aboard almost two months prior...although it was stupid of me to leave without reconnecting the anchors to their chains. I could have at least dropped them quickly if I needed it.

So what would you have done in the ICW with 30 minutes of light left, no engine, no backup, no anchors. (For the record, without having the backup we wouldn't have left in the first place without the windlass)

Second time was in the middle of the Gulf of Mexico, the water pump started leaking and we considered shutting down the main and running on the backup while we fixed it. In the end we didn't and chose to continue as it was and fix it at the dock two days later. But had it gotten worse we would have.

This is why I'm lusting after a twin screw, although the economics are a lot worse.....

Previous boat was single screw and had a backup propulsion system....... 400 square feet of dacron.....

I'm not answering your question about usage of a back-up system, but if I had a single screw as I used to, I'd be tempted to look into a diesel outboard. Apparently Yanmar makes a 50 hp model. not sure if legal in U.S., and storage & rapid deployment would take some thought and engineering, but I like the idea of completely separate system. Has anyone tried this?
Dawdler

Why not two small twins?

My engines come to 348hp total.

Menzies,
I'm with you in preferring two small twins. I was thinking danderer had a single and was contemplating adding a back-up propulsion system....

menzies said:

Why not two small twins?

My engines come to 348hp total.

Click to expand...

I think OP means he's already got a single-screw boat, and if so that "twin" ship has already sailed, so to speak...

I could imagine an electric motor driven off a genset. Don't know as an actual implementation like that would be best with another shaft/prop, or whether it could be clutched into driving the main shaft/prop.

Which in turn suggests a clutching mechanism, probably no small problem, would have to also be able to disconnect the main shaft from the main engine.

Relying on the main shaft/prop would be building in a dependency. OTOH, it may be practically easier/better/cheaper -- and good enough -- for very occasional circumstances.

-Chris

I see.

Well, what about setting your genset up to connect to the shaft. That is another popular method.

ranger42c said:

I could imagine an electric motor driven off a genset. Don't know as an actual implementation like that would be best with another shaft/prop, or whether it could be clutched into driving the main shaft/prop.

Which in turn suggests a clutching mechanism, probably no small problem, would have to also be able to disconnect the main shaft from the main engine.

Relying on the main shaft/prop would be building in a dependency. OTOH, it may be practically easier/better/cheaper -- and good enough -- for very occasional circumstances.

-Chris

Click to expand...

I like this idea. If I was going to go to the trouble, I'd want a separate shaft and prop, I think.

back to outboards--if you like the generator for energy idea--what about using an electric outboard? Torqeedo makes a 40 and 80 hp model. provides not only redundancy in shaft/prop, but also potentially steering.
Any thoughts? Actually, just read that the electric outboard uses high voltage, so it's probably not practical. back to diesel.....

Aren't two engines twice the problem and twice the expense?

Greetings,
"Aren't two engines twice the problem and twice the expense?" NOT if you have the right anchor...

Sweet!!! Another singles vs twins thread!

Edit: I believe that huge thread was started with MarkP as the op as the result of a thread split??? Hmmmm, Mark always seems to be an early poster in this subject

Dawdler said:

back to outboards--if you like the generator for energy idea--what about using an electric outboard? Torqeedo makes a 40 and 80 hp model. provides not only redundancy in shaft/prop, but also potentially steering.
Any thoughts? Actually, just read that the electric outboard uses high voltage, so it's probably not practical. back to diesel.....

Click to expand...

Maybe there's a way? Even a separate genset, if necessary?

An electric outboard would weigh much less than a diesel outboard, I think.... so maybe storage, mounting, etc. issues would be more easily managed.

-Chris

what about using an electric outboard?

A hp in a boat engine will make about 20 lbs of push.

At say 2 GPH perhaps 30-35HP is sent down the shaft for about 600-700 lbs of push.

An outboard with 20-40 lbs of push is not going to get much boat movement.

Unless fitted with a special lower unit and big prop even a 20-25 hp dink motor will have a very hard time at 3k or 4K towing or on the hip.

Actually, that "dink towing on the hip" thing is another possibility for OP's question.


Maybe suggests a larger rather than smaller outboard, plenty of gas, and a connection (towing, pushing, hip) set-up... but maybe that's sufficient to move a 2006 Mainship 34T (see OP's avatar) in an emergency?


-Chris

You can look at failure rates and probabilities all you want, but any statistician will tell you that a failure can still happen anytime. And any boat owner can confirm this.

So I think the real question is what are you going to do when any given failure occurs. You have three choices:

1) Work around the problem. This is where redundant/backup systems come into play.

2) Fix the problem. This is where carrying spares, tool, and knowledge come into play.

3) Call for help.

Where you are cruising is a major factor in how you approach all of the above, and will typically result in very different decisions between different boats. If you cruise the ICW or other populated areas, many boaters will skip right to step 3 and call for help. No need to carry spares or know how to fix anything. But the further away you get form civilization, #3 ceases to be an option and you must be able to handle the problem in steps 1 and 2, i.e. work around the problem or fix it. This is where you see boats with critical systems that are redundant, and with spares tucked in every corner of the boat.

ranger42c said:

Actually, that "dink towing on the hip" thing is another possibility for OP's question.

Maybe suggests a larger rather than smaller outboard, plenty of gas, and a connection (towing, pushing, hip) set-up... but maybe that's sufficient to move a 2006 Mainship 34T (see OP's avatar) in an emergency?
-Chris

Click to expand...

I was able to get my old 34 Mainship to move with an 8 hp outboard/dink setup. But if there was any wind or current I don't think it would move very well.

I've been single engine boating for 25 years without a backup. Have I had shut downs? Yes a few times but they were all (but one) fuel related and I was able to get the engines running again, sometimes in harry situations, sometimes not.

On our boat the backup is exact duplicate of the main engine.
Same spares carried for the both of them.
We've never had a motor or trans failure however we have had ropes,nets etc stop a shaft.
The sound of silence is not a song I like to sing when underway.
It's nice to have redundancy when Murphy pays a visit.
Although the guy who owns this seems to have taken that argument a bit further along than me.

Thread drift is like the tide it seems - you ain't going to stop it. *sigh*

No Mast - thanks. So 1 event and 1 "near" event, both on the main engine without compromised supporting systems (fuel, prop/shaft).

TwistedTree - I don't disagree with most of your points. However, I do think there is value in understanding the MTBF of major elements of the propulsion system. How one chooses to address the three choices you cite is in part determined by the the likelihood of a problem occurring. Certainly statistics can't absolutely predict what will happen to a you in the next 60 seconds but there is still value there imho.

In a likely hopeless attempt to clarify things, I was looking for hard data to decide the value of an auxiliary propulsion option on a to-be-purchased single-engine, offshore-capable trawler that will spend some limited time offshore.

Anyone else have experiences to share (including "I've got a backup engine and have never needed it")?

I thought this thread was about how to install a diesel outboard (nevermind its not available in USA) on a Mainship 34 against the owners will. Or an electric trolling motor to the bow effectively making a Mainship bass boat against the owners will.

twistedtree said:

You can look at failure rates and probabilities all you want, but any statistician will tell you that a failure can still happen anytime. And any boat owner can confirm this.

So I think the real question is what are you going to do when any given failure occurs. You have three choices:

1) Work around the problem. This is where redundant/backup systems come into play.

2) Fix the problem. This is where carrying spares, tool, and knowledge come into play.

3) Call for help.

Where you are cruising is a major factor in how you approach all of the above, and will typically result in very different decisions between different boats. If you cruise the ICW or other populated areas, many boaters will skip right to step 3 and call for help. No need to carry spares or know how to fix anything. But the further away you get form civilization, #3 ceases to be an option and you must be able to handle the problem in steps 1 and 2, i.e. work around the problem or fix it. This is where you see boats with critical systems that are redundant, and with spares tucked in every corner of the boat.

Click to expand...

There's no towing service where we live, and few boats, so we have a 9.9hp outboard kicker mounted to the swimstep on a swiveling bracket. Have not needed it because of a breakdown...yet.

It's a Lehr propane ob which doesn't need to be winterized (coldest we've gone out in so far was -15C, or 5F) and the propane stays good for years (decades?) so it starts right up every time with little coddling from me.

Theory is, with a 20lb propane tank, the Lehr 9.9 would give us over 10 hours of fuel at 3/4 throttle to either get back home or get to a safe anchorage...then we could work on the main engine in relative comfort/safety, or wait for help if it came to that.

Badger is our first boat and I'm no mechanic, so the kicker gives me relative peace of mind.

Only once have we had engine trouble...we anchored in a small, completely exposed bay to do some fishing and the engine wouldn't start. The trouble shooting section in Nigel Calder's book had us up and running in under 15 minutes (corrosion on terminal between ignition and starter) so not a serious breakdown.

CPseudonym said:

I thought this thread was about how to install a diesel outboard (nevermind its not available in USA) on a Mainship 34 against the owners will. Or an electric trolling motor to the bow effectively making a Mainship bass boat against the owners will.

Click to expand...

MurrayM said:

There's no towing service where we live, and few boats, so we have a 9.9hp outboard kicker mounted to the swimstep on a swiveling bracket. Have not needed it because of a breakdown...yet.

It's a Lehr propane ob which doesn't need to be winterized (coldest we've gone out in so far was -15C, or 5F) and the propane stays good for years (decades?) so it starts right up every time with little coddling from me.

Click to expand...

I forgot about those. Sounds workable.

FWIW, we used to have a single engine diesel -- earlier model, 34' Mainship III -- and never had a breakdown, never needed auxiliary propulsion.

-Chris

We've got a single engine and I'm looking for a way to mount the 15hp dinghy engine as an auxiliary should it be needed. I like the swim platform idea above! In the 100 or so hours we have used the trawler so far we have not needed auxiliary propulsion.

I've never owned a single engine boat, so I'm not sure my input is relevant. I can count 6 major times when I was glad to have multiple engines and drive trains. Four were mechanical issues with one engine or another, never both thankfully. The remaining two were fuel issues. There were also several more minor issues when one engine just decided to stall out, usually due to a shift cable that refused to stay properly adjusted, and usually when I was making a dock or a lock and really needed it. As often as not, it would fire back up within a minute or two, after some swearing and furious throttle jiggling.

It was an exciting three summers.

The next boat will have a single diesel and a bow thruster. I doubt It'll have any kind of backup powertrain for simplicity's sake, but I'm going to keep that main engine as clean and happy as I possibly can. My backups will be 1. anchor, 2. repair, 3. dink, and 4. towboat US.

I was on the boarder, but voted Yes to using backup due to a main engine issue. I didn't actually have to use the backup, but if I have been an hour or two further away from port, I definitely would have. Twice my main engine developed a serious coolant leak and was well on the way to becoming completely disabled. Another hour and I would have been running on the wing engine with no hope of repairing the main even though I had most of the required parts on board. I think this is a good illustration of how a backup can be required.

danderer said:

TwistedTree - I don't disagree with most of your points. However, I do think there is value in understanding the MTBF of major elements of the propulsion system. How one chooses to address the three choices you cite is in part determined by the the likelihood of a problem occurring. Certainly statistics can't absolutely predict what will happen to a you in the next 60 seconds but there is still value there imho.

Click to expand...

Yes, I completely agree. It's all about probabilities. But since you don't know WHEN something will break, I argue you need to sort out what you will do when it does break. How screwed will you be? If you are in the middle of the ocean and your engine dies and you have no alternate, you are pretty screwed. If the same happens off the coast of Florida, oh well, no big deal and you'll have a good story to tell.

I went so far as to create a giant document that walks through every critical system on the boat and addresses "what if" various things break. It was a great exercise, and drove my spare parts strategy. It also exposed some vulnerabilities that I didn't expect. It's not a necessary exercise for most boats/boaters, but if you plan to venture to remote locations, I would recommend doing it.

My backup is TowBoatUS.

I'm a single engine boater.

98% of my perceived boat use will be with in range of Tow Boat US, Seatow, or the USCG. For the other 2% of the time I'm comfortable with the laws of probability. Simply, Charles Lindbergh flew across the Atlantic once. The odds of engine failure on that one trip were pretty small. If he had done the flight numerous times, the odds of having a failure increased dramatically, ruling out a single engine aircraft.

If I felt the percentage of time out of the tow boat zone were high enough to warrant back up propulsion, I would have twins.

Ted