sloboat wrote:
So, does anyone want to discuss drive line efficiency tradeoffs/concepts/options? I really was trying to spark a little techno discussion with a twist on the single vs twin theme (the subject of the thread).
Don't know about the technology, but there seem to be a ton of suggestions for how to repower with this engine or that one, use one engine to drive two props, diesel-electric power,*and so on.* They all cite higher efficiency as the benefit.
And I expect that if one could wave a wand and have the conversion installed*and running in their boat, there would be an efficiency increase, at least to some degree.
What I've not seen any of these armchair theories addres, however, is the true cost and true value of the conversion.* They say, "Just buy such-and-such*an engine from an industrial equipment junkyard, marinize it, mate it to such-and-such a transmission, rework the propshaft, bearings, etc., and there you*are."*
All of these proposals require modifications, in some cases very extensive, to the boat.* Engine stringers, engine mounts, shaft alleys, shaft supports, fuel systems, etc. are all candidates for alteration.* If all this is done by a professional installer, the labor cost will be astronomical.* If the mods and installation is done by the boat's owner, the time could stretch into months, years......, and the learning curve could be almost vertical, with lots of trial and error, hence more time and more expense.
One could probably power an existing trawler with a Coleman camp stove if one worked at it hard enough.* What I would want to know is, in the end, would the assumed increase in effeciency pay back the real money plus the value of the person's time, plus the time the boat was unusable?* Is anyone in the financial or age (retired) bracket required to undertake this sort of thing going to live long enough to see the benefit?
Versus simply continuing to use their boat complete with its less-than-ideal powertrain?
When we had the worn-out engine mounts on our FL120s changed a few years ago, the shop found that the correctly rated mounts would*put the engines a bit too high and they would hit the underside of the cabin sole.* The original mounts, installed by the factory, had been undersized for this very reason.* So the question we had to answer was---- 1) do we have new, custom-fabricated mount brackets made for each engine to provide the proper clearance, 2) do we have the engine stringers cut down to provice the proper clearance, or 3) do we simply install brand new undersized mounts identical to what the factory installed when they built the boat?
The estimated cost to do 1) or 2) was significantly over $10,000.* The cost to do 3) was $50 per mount plus two day's shop labor.* Theoretically, option 1)*or 2) was the most ideal solution.* But given that the eight*original undersize mounts had gone over 30 years before requiring replacement, we figured that spending a bit over $3,000 to have the same kind of mounts installed was the far more sensible solution (a decision supported by our diesel shop).* The boat was out of service for only two days, and by the time the mounts need replacing again, we'll proably be dead or close to it.* And we saved at least $7,000 that we could put toward something else, like fuel, maintenance, unexpected repairs, etc.
Repowering an existing boat with something totally different than what was put in it can seem like a good answer to the search for increased efficiency, but I wonder if it really is when all the actual costs and time value are added up at the end of the day.
-- Edited by Marin on Tuesday 19th of May 2009 04:26:30 PM