Cruising RPM for a Crusader 454

[BSilver177]

Can anyone out there tell me what a good typical cruising RPM would be on a
boat with twin Crusader 454 (350 HP) engines. Also the max safe cruising RPM.
Thank you.

[Peggie Hall]

BSilver177 wrote:
>
> Can anyone out there tell me what a good typical cruising RPM would be on a
> boat with twin Crusader 454 (350 HP) engines. Also the max safe > cruising RPM.

Just about all planing hull boats with gas engines should get on plane
and hold it (with the aid of trim tabs) at about 3000...up to about 3400
is the most economical--and the most comfortable--cruising range...after
that, the second carb barrels open up and the fuel consumption curve
rises steeply with every increased rpm. As for the max. safe cruising
speed--as far as your engines are concerned, up to the red line on the
tach (usually about 4500)...but the safe max should be determined by
conditions--the seas, your skill and experience at handling them, how
congested the traffic is, your knowledge of the bottom...there are
plenty of circumstances in which the safe maximum cruising speed is
below 1500.

Peggie

[TenSpeed 2]

need to know what size boat you have but in general crusing around 3000 to 3100
is good you will go into 4 barowl which will eat up gas at 3200 to 3300 rpms

[Bryon Kass]

BSilver177 wrote:
>
> Can anyone out there tell me what a good typical cruising RPM would be on a
> boat with twin Crusader 454 (350 HP) engines. Also the max safe cruising RPM.

> Thank you.
At 3200rpm those engines should be happy. Running 75% is OK for
continuous use of most gas marine engines. The problem is your
wallet. At 3200 the props will absorb 50% of max hp or 18gph per
engine. At 36gph ouch, your wallet will be hurting or Visa melting!
You can however depending on the hull the engines are in get away
with cruising in the 2400-2800 rpm range and cutting your fuel use
about half that. I prefer diesels as the same hp output uses half
the fuel and you can continuously run them 90% rpm.
Bryon Kass
webmaster and
Custom Design
150 Mechanic St.
Foxboro, MA 02035
508-543-9068 or fax 508-543-5127, Foot yard 508-384-2415
in THE ENGINE ROOM http://home.ici.net/~cusdn

[Prof. Keith Ronald]

Lets go slower, I usually cruise at 1700 (37 Egg)giving 8 knots, what
consumption should I expect?
P.S. don't all gas engines do one nmile to the gallon mile?
kro...@uoguelph.ca

[john...@dangerman.com]

As everyone has noted - speed = gas consumption. I suggest you make a
graph plotting RPM vs gph to find your hull's particular sweet spot.

My boat liked 3100 for a fast cruise, but 2700 was best for
consumption.

[BSilver177]

Thanks for the suggestion. I plan on getting a fuel flow meter from Flo Scan.
I've used their system in aircraft.

[Michael J Porter]

In article <35D03C...@ici.net>, Bryon Kass <cu...@ici.net> wrote:
=>BSilver177 wrote:
=>>
=>> Can anyone out there tell me what a good typical cruising RPM would be on a
=>> boat with twin Crusader 454 (350 HP) engines. Also the max safe cruising RPM.
=>> Thank you.
=>At 3200rpm those engines should be happy. Running 75% is OK for
=>continuous use of most gas marine engines. The problem is your
=>wallet. At 3200 the props will absorb 50% of max hp or 18gph per
=>engine. At 36gph ouch, your wallet will be hurting or Visa melting!
=>You can however depending on the hull the engines are in get away
=>with cruising in the 2400-2800 rpm range and cutting your fuel use
=>about half that. I prefer diesels as the same hp output uses half
=>the fuel and you can continuously run them 90% rpm.
=>Bryon Kass
=> webmaster and
=> Custom Design
=> 150 Mechanic St.
=> Foxboro, MA 02035
=> 508-543-9068 or fax 508-543-5127, Foot yard 508-384-2415
=> in THE ENGINE ROOM http://home.ici.net/~cusdn

Lower RPMs do not necessarily equal better miles per gallon. You
will burn less fuel per hour, but your speed will drop off by a
good bit, too. You can get Floscans and hook them up to a GPS and
get miles per gallon on the display ... for a decent of amount of
money, though.

For instance, most 25' boats equiped with a 5.7L I/O get their best
mpg at about 3500 rpm. My old boat definately has a speed/rpm hump
in the curve right around that point.

Don't know what would be best on your boat with the 7.4Ls.

Mike

[Allen Perrins]

Hi
With 5.7 or 7.4's with a four barrle carb, keeping of of
the second two ports usually
leads to max efficiency.
AL

Michael J Porter <mi...@copland.udel.edu> wrote in article
<6rcjdb$3ma$1...@copland.udel.edu>...