2bucks wrote:
Good point Marin. What do you suppose it costs extra to carry the spare engine?
The cost of a spare driveline is basically double that of having just one on board.* The only cost that's not exactly doubled is fuel, but as you say,*it's probably at least half again as much a single.
However I'm not sure about wearing out things twice as fast a single.* In theory, the fuel pumps on each engine of the twin will last as long as the fuel pump on the only engine of a single, assuming the same engines and pumps.**The belt on*either one of my FL120s should last as long as the belt on someone elses' only FL120.* So in terms of service life, there should be no difference between a single and a twin (assuming the same kind of boat, engines, etc.).* The big difference is cost, and the time spent performing mainenance or repairs.
The main reason we have invested in things like spare pumps, etc. is so that we have them on hand when we need them rather than perhaps having to wait one or more weeks to get one in.* We use the boat year round and don't want to be sidelined because we have to wait for a part.* The parts we carry-- like pumps and toilet rebuild kits and such--- are not selected based on the liklihood of being needed but on the liklihood of not being readily availalble when we need them.
And while your spare prop never gets dinged sitting in the bilge, it's also not going to push the boat while it's sitting in the bilge.* So you have to go to the hassle of taking off the damaged prop and putting on the spare one.* Our spare prop is already mounted
* And so far, in the eleven years we've been running the boat on a year-round basis, we've not dinged, nicked, or even scratched either of the props.
I also don't want to interrupt a run to deal with a breakdown even if I had the part and tools on board.* Pitching and rolling in the middle of the Strait of Georgia on a bad day while I replace a fuel pump or whatever is not my idea of fun.* So to me it's well worth doubling the cost of maintenance to not have to worry about dealing with a drivetrain problem in the middle of going somewhere.* When through ignorance I let an engine get a slug of air during a fuel transfer last year, I knew why it stopped and I knew how to bleed it to get it going again.* But we had a boatload of friends on board, they had committments they had to be home for that evening, so I simply tied off the shaft of the "dead" engine and we continued on our way back to Bellingham at*about the same*speed we'd been going before.* Our friends made their appointment and I bled the engine the following weekend.
Mind you, I'm not trying to make the case that a twin is better or more reliable than a single.* When we went shopping for a*GB36 we didn't care if it was a single or* twin.* We'd been chartering a single and were perfectly comfortable running it.* But as it happened the boat that best met our needs and budget was a twin.* Plus as I've said before, I like running engines.* The more the merrier.* I'd have three or four*of them if I could.
Because we keep our boat in Bellingham and we have a 24 foot VHF antenna we hear a lot of the San Juan and Gulf Island radio chatter even if we spend the weekend on the boat in port.* It's amazing how many boats we hear during the summer on nice weekends*calling for a tow after their engine quits.* Granted, some of them are "out of fuel" calls, so the number of engines is irrelevant.* And some of them are sailboats*so*multiple engines*wasn't an option.* But many of them are single-engine powerboats and Vessel Assist seems to do a very good business during the summer months dragging them home on the end of a rope.
But much more imporant than my liking to run as many engines as possible or the perceived reliability factor of having two engines is the fact that even though my wife had no qualms about the single-engine GB we charted, she has admitted that she's more confident with two engines under the floor.* And keeping one's boating partner as happy as possible is right up there at the top on my priority list.
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-- Edited by Marin on Monday 17th of August 2009 05:06:56 PM