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"The boat was originally
set up for diesels, as they were offered as an option," says Dunn,
"so the tanks had return lines and the raw-water intakes were large
enough. I also lucked out on the running gear. According to Yanmar, I
needed inch and a half shafts, and that’s what I had." He says
that getting the new engines to fit the existing beds is one of the major
problems with a repower job. "It’s not just a matter of cut
here and take some off there until you’ve got a fit," he points
out. "If your guy second-guesses, not only are you wasting time,
but you could be opening yourself up to a lot of trouble later on."
Not only did Westberg modify the Ocean’s stringer system to accept
the Yanmars, but he even customized a gutter system around the new engine
boxes so that any water accumulating there would run out.
Dunn says actual installation
time amounted to about two weeks, although Moonshadow was tied
up for most of the winter because Westberg was busy with other work, the
weather didn’t always cooperate, and Dunn was in no hurry to get
it done. All told, Dunn says fiberglass work amounted to 53 hours, removal
of the old engine boxes and fabrication of the new ones took 14 hours,
and 18 hours were required to install the new engines, including connecting
the new gauges. "The yard bill came to $8,028.43 just as we hit the
starter button," he says.
Were the results worth
it? Dunn reports he was averaging about 26 gph with the gasoline engines
at a cruise speed of about 20 mph at 3200 rpm. At that rate he had a 145-NM
range based on his 210-gallon fuel capacity. With the Yanmars he says
he’s burning less than 20 gph at a cruise speed of almost 30 mph
at 3350 rpm, a speed I confirmed with our Stalker radar gun and a GPS
when Dunn took me for a ride. That works out to a nautical-mile range
of 247. When he bumped the rpm to 3600, Yanmar’s recommended cruise
speed, I clocked a speed of 32.4 mph. "In addition, I’ve got
about a 300-mile range on the boat, where before [with the gasoline engines]
I doubt I had half that," he laughs as he admits to once running
out of gasoline in the C&D Canal on a trip from Annapolis to New Jersey.
A key concern in the
success of this installation was the choice of props. Dunn wasn’t
sure the original props–three-bladed, lightly cupped 20x24s–would
do the job, but felt that at the very least he could use them as spares.
(A dinged prop can result in expensive down time for a charter boat.)
Besides, he wanted to make sure he had the right props for the new installation.
"Given all the work I put into this project," he says, "the
last thing I needed was the wrong props."
Dunn ended up purchasing
a set of 19x22 ISO Class I (high-accuracy), four-bladed Austral props,
also slightly cupped, for $1,600, from Steve King at Black Dog Props of
Stevensville, Maryland. "I heard a lot of good things about Prop
Scan, and Black Dog had been involved in several repower jobs with Yanmars
and had all the power curves for the engines," he explains. "When
they ran the numbers through the computer program, it came up four-blade."
I asked Dunn if we could
compare the three-bladed props with the four-blade ones, and he agreed
(see charts above). Our average of four runs for the original wheels was
29.2 mph at 3350 rpm, his usual cruising speed. When we pushed the engines
to 3600 rpm, Yanmar’s recommended cruise speed, the average increased
to 32.4 mph. With the Australs installed, I measured almost the same speed
at 3350–29.7 mph–but our top-end average was 33.9 mph, a solid
mile and a half faster. More important, however, was the overall increased
smoothness out of the hole as well as during cruising speeds.
Dunn figures he’s
invested a total of $113,379.43 in the Ocean, which he guesses now has
a value of around $125,000. (He says he found a similarly equipped Ocean
29 with an asking price of $129,000 on the Internet.) Little wonder that
while admitting that repowering is not for everyone, Dunn sums up his
project this way: "As far as performance, economy, range, and safety
are concerned, I’m 100 percent satisfied."
If you rack up a lot
of hours annually, repowering may make sense. If you’re considering
taking on such a job, follow Dunn’s advice and do a lot of research.
Understand your boat’s limitations and what is practical for your
needs, rely on a mechanic with a solid track record in repowering, and
settle on a firm work schedule before you sign a contract. The more you
know beforehand, the less you’ll worry about come launch day.
Moonshadow Charters
Phone: (609) 709-4026 or 492-8659.
Penna’s Marina
Phone: (609) 492-0191. Fax: (609) 492-1954.
Prop Scan USA
Phone: (877) 767-7226. Fax: (757) 485-7839. www.propscanusa.com.
Yanmar Phone:
(847) 808-2213. Fax: (847) 541-2161. www.yanmar.com.
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