Backup

[sunchaser]

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

Only to the naysayers and agitators. Now about those twins in Singapore -----

 

[O C Diver]

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

Yes.

The risk of both engines failing on the same day are exponentially smaller than just one (with the exception of shared fuel or battery source). However, statistically one of two engines failing is twice as likely as one. While they won't burn twice as much fuel for the same speed, almost all other costs (purchase, installation, and normal maintenance) will be twice as much.

Ted

 

[danderer]

However, statistically one of two engines failing is twice as likely as one.

Is that really true?

I've seem some anecdotal data suggesting that some twin-engine owners (of both boats and aircraft) may have the feeling that--because they have two engines--each engine may not need to be maintained to quite the same level a single-engine would be. Or to put it another way, a SE owner might be a bit more obsessive maintaining their sole power source.

Again, this is just anecdotal but jives with some things I've seen.

 

[O C Diver]

Is that really true?

I've seem some anecdotal data suggesting that some twin-engine owners (of both boats and aircraft) may have the feeling that--because they have two engines--each engine may not need to be maintained to quite the same level a single-engine would be. Or to put it another way, a SE owner might be a bit more obsessive maintaining their sole power source.

Again, this is just anecdotal but jives with some things I've seen.

I agree with what you are saying.

If that were the case, then one of two engines (in a twin engine boat) failing would be more than twice as likely as a single engine boat.

Statistically it's probably better to say that the risk of a single engine failuring increases as a multiple of the number of engines in the boat.

Ted

 

[RT Firefly]

Greetings,
Mr. d. Having had both a single and twins, it's not that big a deal, for me anyway, to double up the maintenance (oil changes etc.) when one does it. Yes, more time and more expense but...

Could possibly be that single or twin owners who defer maintenance are just naturally negligent and # of engines is not really a factor. I'm sure we've all seen YW listings where the living quarters show well but the ER spaces are disasters. Just skewed priorities IMO.

 

[danderer]

TwistedTree - How one chooses to address the three choices you cite is in part determined by the the likelihood of a problem occurring.

Another factor in determining how to plan for failure is the cost of the solution. Belatedly doing some research on Nordhavn (wing-engine) and KK (hydraulic drive on the main shaft powered by the generator)--well, it turns out the backup is cheaper than I would have thought: it'll add about 2% to the cost of a new build.

Seems like that is a no-brainer for doing any offshore work, regardless of the stats.

 

[DHeckrotte]

I've moved a 16000 lb 38' sailboat a couple miles with a 2hp motor on the dink. Tied the dink on the 'hip' so the admiral at the helm and I could speak. Got up to about 4 kts in calm (had there been wind...). Drove right up to a mooring and moored.

Thinking that our 26000 lb 39' trawler ought to move with a 15hp motor on the dink, but I doubt that she'd be as easy to control as the sailboat was.