On Wed, 24 Nov 2004 22:23:34 GMT, "Eisboch"
wrote:



Al wrote in message
. ..


I'm in the process of purchasing a 2002 Cruisers with Caterpiller 3126
engines. Please give me your honest opinion about these engines.
Thanks,


One other item I forgot in the other post:

How many hours on the engines? The Cat people told me in no uncertain terms
that the engines should be serviced by Cat at 250 hours and this service was
the most important one to have done. (post break-in).

If the Cruisers you are looking at has over 250 hours, I'd verify with the
owner that the service had been done, otherwise damage can occur, according
to Cat. Have an oil analysis done also to make sure there are no developing
problems and to establish a baseline for your own records.

There's something that puzzles me about marine diesels.

I assume that these are high revolution diesels much like the one in
my truck. How do boats like that Topaz I'm looking at generate their
speed - gearbox?

Oh, and while I'm on the subject, how does a engine synchro work? I
have an idea, but I'm not sure.

Later,

Tom
-----------
"Angling may be said to be so
like the mathematics that it
can never be fully learnt..."

Izaak Walton "The Compleat Angler", 1653

Short Wave Sportfishing wrote in message
...


I assume that these are high revolution diesels much like the one in
my truck. How do boats like that Topaz I'm looking at generate their
speed - gearbox?

That and prop pitch and diameter. My Navigator engines (Volvo) are rated at
2800 RPM with a recommended cruising RPM or 2600 RPM. I can't remember the
transmission gear ratio - I think it is 2:1, but I am not sure. The props
are 30" dia. by 30 pitch.

The Egg with the 3126 Cats was also rated at about 2800 RPM WOT. Again, I
don't remember the gear box ratio, and the props were something like 25"
dia. by 28 pitch.

Many of the serious sports-fish types have "trolling valves" installed on
the transmissions that allow a certain amount of hydraulic slip that permits
the boat to troll at a lower speed. Otherwise, the only way to troll below
about 6 knots was to put one transmission in neutral and work with one
engine and even then, on some of the really high-powered boats, you can't go
slow enough.


Oh, and while I'm on the subject, how does a engine synchro work? I
have an idea, but I'm not sure.

On both the Navigator and the Egg, there is a mechanical tachometer take-off
on the main crankshaft pulley on the front of the engines. A cable, similar
to an old-fashioned speedometer cable, transfers the rotational
speed of the tach to a hydraulic controller that is connected to the
throttle of the "slave" engine.

In operation, turning the synchro on disconnects the manual throttle control
of the slave engine and the hydraulic controller takes over and adjusts the
slave engine throttle to match the master engine RPM.
Both engines are now controlled by adjusting the master engine throttle
only.

I was amazed at how well they work. Although you can "tune" by ear, on
bigger boats it is sometimes hard to detect a 20 or 30 RPM difference. When
I first got the Navigator, I used to control both throttles manually at
first and thought I was doing a great job in keeping them in sync. I
noticed one day that the starboard engine was running about 5 degrees hotter
than the port engine after a long run. The temps were still well within
normal, but, being a nerd, I started worrying about why. A friend was with
me who is far more experienced than I and noticed I didn't have the syncs
on. At his suggestion I engaged them and within 5 minutes both engine temps
were identical.

Does that help?

Eisboch


Later,

Tom
-----------
"Angling may be said to be so
like the mathematics that it
can never be fully learnt..."

Izaak Walton "The Compleat Angler", 1653

On Wed, 24 Nov 2004 23:46:29 GMT, "Eisboch"
wrote:


Short Wave Sportfishing wrote in message
.. .


I assume that these are high revolution diesels much like the one in
my truck. How do boats like that Topaz I'm looking at generate their
speed - gearbox?

That and prop pitch and diameter. My Navigator engines (Volvo) are rated at
2800 RPM with a recommended cruising RPM or 2600 RPM. I can't remember the
transmission gear ratio - I think it is 2:1, but I am not sure. The props
are 30" dia. by 30 pitch.

The Egg with the 3126 Cats was also rated at about 2800 RPM WOT. Again, I
don't remember the gear box ratio, and the props were something like 25"
dia. by 28 pitch.

Many of the serious sports-fish types have "trolling valves" installed on
the transmissions that allow a certain amount of hydraulic slip that permits
the boat to troll at a lower speed. Otherwise, the only way to troll below
about 6 knots was to put one transmission in neutral and work with one
engine and even then, on some of the really high-powered boats, you can't go
slow enough.


Oh, and while I'm on the subject, how does a engine synchro work? I
have an idea, but I'm not sure.

On both the Navigator and the Egg, there is a mechanical tachometer take-off
on the main crankshaft pulley on the front of the engines. A cable, similar
to an old-fashioned speedometer cable, transfers the rotational
speed of the tach to a hydraulic controller that is connected to the
throttle of the "slave" engine.

In operation, turning the synchro on disconnects the manual throttle control
of the slave engine and the hydraulic controller takes over and adjusts the
slave engine throttle to match the master engine RPM.
Both engines are now controlled by adjusting the master engine throttle
only.

I was amazed at how well they work. Although you can "tune" by ear, on
bigger boats it is sometimes hard to detect a 20 or 30 RPM difference. When
I first got the Navigator, I used to control both throttles manually at
first and thought I was doing a great job in keeping them in sync. I
noticed one day that the starboard engine was running about 5 degrees hotter
than the port engine after a long run. The temps were still well within
normal, but, being a nerd, I started worrying about why. A friend was with
me who is far more experienced than I and noticed I didn't have the syncs
on. At his suggestion I engaged them and within 5 minutes both engine temps
were identical.

Does that help?

Very much - that's pretty much how I thought they worked. I've worked
on three engine pulling tractors that use much the same concept - a
master and two slaves in that case. It was quite the deal - turbo
diesels. It was quite the setup.

Thanks for the info.

Later,

Tom

In article ,
Short Wave Sportfishing wrote:


On Wed, 24 Nov 2004 22:23:34 GMT, "Eisboch"
wrote:



Al wrote in message
. ..


I'm in the process of purchasing a 2002 Cruisers with Caterpiller 3126
engines. Please give me your honest opinion about these engines.
Thanks,


One other item I forgot in the other post:

How many hours on the engines? The Cat people told me in no uncertain terms
that the engines should be serviced by Cat at 250 hours and this service was
the most important one to have done. (post break-in).

If the Cruisers you are looking at has over 250 hours, I'd verify with the
owner that the service had been done, otherwise damage can occur, according
to Cat. Have an oil analysis done also to make sure there are no developing
problems and to establish a baseline for your own records.

There's something that puzzles me about marine diesels.

I assume that these are high revolution diesels much like the one in
my truck. How do boats like that Topaz I'm looking at generate their
speed - gearbox?

Yep. That and the pitch of hte prop. For some boats you have a problme
where the lowest speed you can make is in excess of 6 knots, which is a
problem for trolling. The "fix" for tha tis trolling valves that
intentionally drop the clutch pressure and allow them to slip (controlled) -
they work, but if you come off idle with them turned on, you will destroy a
gearbox in seconds. So they do require discipline.....

Oh, and while I'm on the subject, how does a engine synchro work? I
have an idea, but I'm not sure.

There are two basic systems out there...

The mechanical sync - which Glendinning is known for - works on the tach
drives. Both engine tach cables are run to the unit. WHen it is turned on,
the unit computes a difference between the two tach drive speeds, and uses
that to slew the slave throttle. until the difference is zero. It is
extremely effective and smooth, and is quite simple.

The elcetronic engines can sync electronically, since they're "fly by wire".

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