"Oliver Fleming" wrote in
:
The smaller the diesel engine the harder it has to work to achieve
the
hull speed of the boat.
(Square root of the waterline length X 1.34)
You need the minimum size diesel that will achieve this. If 50
horsepower does it then that is what you need.
Diesels must be worked hard or there are several issues with
glazing and
smoking. A hard worked diesel engine is a happy engine.
If you want a planing fast boat then you must buy more horsepower.
However a Trawler type 'Slow Boat' only needs minimum power.
They are cheaper to run per hour as well.
Oliver Fleming
Dead on and very well said. I see overpowered Nordic Tugs PLOWING down
the ICW through Charleston on the Florida Express trying, in vain, to
drive them like a bass boat with those overpowered "Express" engines.
All they do is make a huge bow wave to crash into everyone's boat and
dock near shore. With that big a bow wave, they must be just guzzling
diesel. It certainly doesn't make speed.
On the other hand, my friend Dan lived aboard a 1980-something Hatteras
56 FBMY with twin 8V92TA (twin turbos) train engines in it driving 32"
screws, Naiad Stabilizers and hydraulic planing fins under the swim
platform you had to climb down to. Dan is NOT a boat captain and could
barely sidle it up to a dock with all this power. He was deathly afraid
of planing it. So, there are these HUGE 735hp twin two-stroker beasts
idling along at 1200 RPM in "trawler mode" for hours on end. The book
says they should have had all kinds of problems...coking, carbon
deposits, all those awful things, glazing, you hear about. Dan never
worked them at all...just idling around. The only time they were "worked
hard" was when I was at the helm, offshore and away from the fishermen
far enough where the monster wake wouldn't sink anyone. It was a sight
to behold with 55 tons riding right up on plane. I trimmed the tabs,
energized the Naiads I'd just fixed others had given up on, and after the
big exhausts cleared their throats of the accumulated carbon in them
(leaving a black trail that looked like a steamship blowing its tubes..
(c
...she ran great! I never saw any evidence of anything dastardly
when I throttled them up to full. All the rest of the time they ran at
just above idle in the ICW or around the harbor.
The diesel engineers pulled both engines apart when Dan sold her for the
new owner to assess their condition. Their condition was outstanding, as
I suspected because they always started dead cold on the second
compression they came to, even in what little winter we have here. They
found one weak spring in the injection and replaced it. Far as I know,
the new owner I've seen when it passes through Charleston, never
mentioned any problems with them, a lot of hours later. He wanted me to
make a drawing of the extensive power distribution system I had installed
for the electronics suite from a separate panel. I mailed it to him in
the BVI.
I don't think running them at so little load so slow hurts them at
all....
My feeling for a trawler is it should have just enough HP to climb its
way up a fairly good sized ocean swell when it's rough outside. 50hp
isn't it, unless you're going to stay in the ditch and never go outside.
I'd want the extra HP to make sure I wasn't going to slide back any more
than is absolutely necessary. But, I think twin 400hp V-8's is stupid.
The boat builders must be doing that to satisfy the demand of buyers whos
lives move at the speed of jets. Those people shouldn't be buying a
trawler in the first place....or a sailboat...
Everyone is in WAY too much of a hurry to "get there"....