I'm considering the purchase of a 2001 Silverton 410 Sportbridge with twin
Gas 8.1L Crusaders (425HP) each

I'm concerned about gas engines in a 41 foot boat. Will it struggle to get
and stay on plane? How will it maintain speed in following seas?

but most importantly, how much gas will it burn??? I've seen the thread
where you divide the HP by 2 for cruising HP and then average 1gph for every
10hp, but we are talking about a 30,000+ pound boat with a flybridge, thats
like pushing a brick through the water...

lastly, anyone know what the approximate cruise speed and RPM's are on this
boat....

THANKS!!!

khessert wrote:
I'm considering the purchase of a 2001 Silverton 410 Sportbridge with twin
Gas 8.1L Crusaders (425HP) each

I'm concerned about gas engines in a 41 foot boat. Will it struggle to get
and stay on plane? How will it maintain speed in following seas?

but most importantly, how much gas will it burn??? I've seen the thread
where you divide the HP by 2 for cruising HP and then average 1gph for every
10hp, but we are talking about a 30,000+ pound boat with a flybridge, thats
like pushing a brick through the water...

lastly, anyone know what the approximate cruise speed and RPM's are on this
boat....

THANKS!!!



Suggested reading....

http://www.yachtsurvey.com/GasDiesel.htm

http://www.yachtsurvey.com/GasNdiesel.htm


It may be worth taking some time to read the details contained in these
articles.

xorbit wrote in :

http://www.yachtsurvey.com/GasDiesel.htm

"We recently surveyed a yacht with a pair of 8V71N (naturally aspirated)
Detroit Diesels rated at 325 hp that hadn't been overhauled since new 1981.
Now, an 8V71 has a 568 cubic inch displacement; the fact that these engines
have a 0.56:1 power/displacement ratio explains why they could run so
long."

There's the engines he's looking for....(c;

I wonder what Pascoe's survey was on that boat, vs the same boat in the
same condition with two way-past-worn-out gas engines that had been changed
3 or 4 times in those 25 years would have been, given his anti-diesel
slant? Obviously, once past the initial cost of two 8V71s, engine costs
have been quite reasonable in 25 years of faithful service.

Big ol' heavy 2-stroke DDs (71s or 92s) with no turbochargers to catch
fire. That's always a winning combination.

Change the oil. Let's go to the Med.

Larry wrote:
xorbit wrote in :


http://www.yachtsurvey.com/GasDiesel.htm


"We recently surveyed a yacht with a pair of 8V71N (naturally aspirated)
Detroit Diesels rated at 325 hp that hadn't been overhauled since new 1981.
Now, an 8V71 has a 568 cubic inch displacement; the fact that these engines
have a 0.56:1 power/displacement ratio explains why they could run so
long."

There's the engines he's looking for....(c;

I wonder what Pascoe's survey was on that boat, vs the same boat in the
same condition with two way-past-worn-out gas engines that had been changed
3 or 4 times in those 25 years would have been, given his anti-diesel
slant? Obviously, once past the initial cost of two 8V71s, engine costs
have been quite reasonable in 25 years of faithful service.

Big ol' heavy 2-stroke DDs (71s or 92s) with no turbochargers to catch
fire. That's always a winning combination.

Change the oil. Let's go to the Med.



I went through every article on Pascoe's site. Very informative. But
he's definitely a sceptic and the site is focused on fiberglass boats
without consderation for steel or other hull materials. Also, pretty
much regardless of what he's discussing, the glass is usually
half-empty. He certainly wants to make sure potential buyers know what
they're getting into.


In the context of this thread, Pascoe states that gas engines are not
appropriate for boats greater in length than the mid-30 foot range.

Those big two-stroke diesels are really something. Real power. (three
Tim Allen grunts here.)

On Mon, 08 Jan 2007 20:35:54 -0600, xorbit wrote:

In the context of this thread, Pascoe states that gas engines are not
appropriate for boats greater in length than the mid-30 foot range.

It's really more a matter of weight rather than length, somewhere
around 15,000 pounds or so. My old Bertram 33 sportfish at 21,000 lbs
was definitely over the line. It had twin 350 hp Crusaders and they
were not nearly enough power, and way too thirsty.

xorbit wrote in :

But
he's definitely a sceptic

No he isn't. He's a first class ass. That's what people pay him for.
More surveyors should be like him. If he says it's crap, it's really crap.

I love diesels, have 3 of 4 diesel vehicles, running on used french fry
oil. But, I must admit once you factor in how little use a boat really
gets for 99% of their owners, he's right about going cheaper gas. The dock
condos hardly need an engine that runs at all, just sitting there like most
do.

Larry wrote:
xorbit wrote in :

But
he's definitely a sceptic

No he isn't. He's a first class ass. That's what people pay him for.
More surveyors should be like him. If he says it's crap, it's really crap.

I love diesels, have 3 of 4 diesel vehicles, running on used french fry
oil. But, I must admit once you factor in how little use a boat really
gets for 99% of their owners, he's right about going cheaper gas. The dock
condos hardly need an engine that runs at all, just sitting there like most
do.

One point not looked into is the resale value of a diesel vs a gas
powered boat. The diesel is always going to have a better resale.

Some points that are hard to quantify are when you have diesel power,
the knowledge that it's much more reliable, your just not going to have
as many problems, if you maintain them and don't abuse them. The boat
will be much more enjoyable with diesels, you've got more power
available when, or if, you want it. You can take a boat load of friends
on board and it's not going to suddenly slow way down, or not get up on
plane. You won't like it when the same boat with diesels fly's on past
you. And it's going to be less painful when it comes time to fill the
fuel tanks.

It's hard to put a price on peace of mind. And I know the price
differance is a lot. But if you could have afforded the diesels, and
you didn't go for them, you'll find that you will regret not getting
them. You'll almost never find someone that has owned a diesel powered
boat (that could afford it) purchases a gas powered boat after that
unless the boat is much smaller.

John

excellent articles...thanx!!!

xorbit wrote:
I'm considering the purchase of a 2001 Silverton 410 Sportbridge with twin
Gas 8.1L Crusaders (425HP) each
[quoted text clipped - 11 lines]

THANKS!!!

Suggested reading....

http://www.yachtsurvey.com/GasDiesel.htm

http://www.yachtsurvey.com/GasNdiesel.htm

It may be worth taking some time to read the details contained in these
articles.

--
Message posted via BoatKB.com
http://www.boatkb.com/Uwe/Forums.aspx/cruising/200701/1

On Mon, 08 Jan 2007 22:14:04 GMT, "khessert" u30800@uwe wrote:

lastly, anyone know what the approximate cruise speed and RPM's are on this
boat....

With the correct props cruising RPMs should be in the range of 3200 to
3400 assuming 4400 to 4800 at WOT (Wide Open Throttle).

Fuel burn will be in the range of 40 to 50 gallons per hour at
cruising RPMs.

Speed is harder to predict but 18 to 20 kts seems reasonable. A boat
that size and weight should really have diesels.

thats kinda what I figured, I was hoping to burn less and go faster than what
I have now (34 Silverton Aft Cabin with twin gas 7.4L crusaders) it's
painful to fill her up...sometimes over $1000...

btw, according to the survey, it does 24.6kts @ 4250rpm (WOT)

I'm gonna need a 2nd job to put fuel in her.....

Wayne.B wrote:
lastly, anyone know what the approximate cruise speed and RPM's are on this
boat....

With the correct props cruising RPMs should be in the range of 3200 to
3400 assuming 4400 to 4800 at WOT (Wide Open Throttle).

Fuel burn will be in the range of 40 to 50 gallons per hour at
cruising RPMs.

Speed is harder to predict but 18 to 20 kts seems reasonable. A boat
that size and weight should really have diesels.

--
Message posted via http://www.boatkb.com