Inboard Outboard never Volvo vs. Older Volvo
I would welcome this groups input on the advantages and disadvantages of the
newer Volvo I/O's compared to the older models.
My first boat, 18' Owens, had a 1960 100 hp Volvo carbureted I/O. As I
recall it had wonderfully miserly fuel economy.
All this talk about DuoProps has me rethinking I/O's for my next as yet
un-finalized boat. It will be trailerable. Perhaps a Catamaran.
Some say:
More maintenance with I/O.
More complicated to get power to the prop.
More prone to sinking due to bellows.
Least expensive to replace engine alone.
The newer DuoProps are easily damaged by debris - even kelp.
Regards,
Jim Garner
Jim,
Some of the major disadvantages with outdrives are pretty much eliminated by
trailering the boat. Corrosion and marine growth due to the outdrives
remaining submerged are eliminated. Maintenance of the lower unit is not
substantially greater than an outboard lower unit, and since you'll
routinely be trailering it you can perform that maintenance when & where you
choose.
Outdrives do have one significant weakness the other drives don't have, and
that's an extra change of direction for the power flow - it comes
horizontally out of the engine, makes a 90 to run vertical down the
outdrive, and then another 90 out the prop shaft. That's one more corner
than outboards or shaft drives make, and hence more opportunity for gear
failures. And to make it worse, one of those joints has to articulate for
steering and trim.
But they make up for that with several advantages. One of them is the
option for a duoprop assembly. I've heard of a few duoprop failures, but
I'm aware of many mariners running hundreds and thousands of hours with no
problems. A 15-20% efficiency improvement at today's fuel prices is pretty
significant. At a 10 GPH burn rate with diesel at $4 per gallon (it's
nearly $5 per gallon here in Juneau, but some of that's due to our current
local power crisis - avalanche took out our hydroelectric and we're powering
100% by diesel, 100,000 gallons per day - so demand is high right now...)
that's around $7-8 per hour, easily thousands of dollars per year. And just
as importantly, it increases your range.
Another advantage is the ability to dynamically trim the boat. You can do
that with an outboard too. Because cats are so much more susceptible to
fore-aft trim problems, being able to adjust trim while running is more than
a luxury.
You can run diesel with its much better efficiency. Modern gas outboards
with fuel injection and computer controls have really improved that
powerplant. But diesel technology hasn't stood still either, and the new
common rail injection diesels are far quieter, more energy efficient, and
generally more refined than their predecessors.
Weight distribution is better than outboards with the engine sitting forward
instead of hanging aft of the transom. A large 4-stroke outboard, say a 200
hp unit, is mighty heavy way out there.
Lots of opinions and lots of opportunities for discussion on this subject,
and it's been pretty much beaten to death on other boating boards.
How big will your new boat be?
Bob Deering
Juneau, Alaska
-----Original Message-----
From: power-catamaran-bounces@lists.samurai.com
[mailto:power-catamaran-bounces@lists.samurai.com] On Behalf Of Jim Garner
Sent: Saturday, April 26, 2008 5:26 AM
To: power-catamaran@lists.samurai.com
Subject: [PCW] Inboard Outboard never Volvo vs. Older Volvo
I would welcome this groups input on the advantages and disadvantages of the
newer Volvo I/O's compared to the older models.
My first boat, 18' Owens, had a 1960 100 hp Volvo carbureted I/O. As I
recall it had wonderfully miserly fuel economy.
All this talk about DuoProps has me rethinking I/O's for my next as yet
un-finalized boat. It will be trailerable. Perhaps a Catamaran.
Some say:
More maintenance with I/O.
More complicated to get power to the prop.
More prone to sinking due to bellows.
Least expensive to replace engine alone.
The newer DuoProps are easily damaged by debris - even kelp.
Regards,
Jim Garner
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