Bob wrote:

But there are some folks that say "upgrade" to more modern model.

Modern isn't always better. I don't know what is going on with small marine
diesels now but I fear my recent experience with aircraft maintenance may be
relevant to boats. If anyone has data to add on these points, I'd
appreciate hearing it.

In aviation, things that used to last for hundreds of hours a couple decades
ago began failing very rapidly about a decade ago. This applies to vital
engine parts like valve lifters and camshafts as well as flight instruments.

The reasons are all the globalization issues. A turn coordinator used to be
built in a place where someone who had been assembling them for 20 years
knew that if one part swung back and forth just a certain way when trial
assembled, it was good to continue. Otherwise the parts needed some
tweaking. The company gets bought by someone who thinks they can make a
profit by increasing effeciency so they fire everyone and hire younger
people who will work for less. All they know is that part A goes into part
B and they have to assemble 20% more than the old crew did or they'll be
looking for a job.

There is a specification and a procedure for heat treating valve lifter
faces. Somebody, or a crew who has been doing it for a long time, knows
something like the fact that letting the kiln cool down with the parts in it
instead of just taking them out is the difference between parts that fail
prematurely and those last. This never makes it into the specification
because it's just the way they've always done it. The company gets sold and
the production is moved to China where they follow the specifications to the
letter but the parts still start failing half way to overhaul time.

A lot of things like engines were designed to be built by artisans who cared
and understood them and have not made the transition to modern times
gracefully. A thouroughly modern engine built on a thouroughly modern
production line with the advantages of computer machining, etc. may be
better. Automotive engines certainly are. I'm not sure that something like
a small marine diesel is better simply because it's a newer model.

If I were replacing an engine in an aircraft and strapping my butt behind
it, I would prefer an engine overhauled by a good overhauler who looked at,
evaluated, and adjusted, each part individually than a brand new one from an
assembly line. I'm not sure this hold true for boats but my first
inclination if I had your engine would be to go for the overhaul.

--
Roger Long

"Roger Long" wrote in news:45b281b7$0$28089
:

All they know is that part A goes into part
B and they have to assemble 20% more than the old crew did or they'll be
looking for a job.


It's the reason Mercedes Benz no longer produces the finest automobiles in
Stuttgart, but builds a piece of SUV crap in Arkansas with the company
logon on it.

They are no longer listed on "The finest cars in the world" lists.....

Don't think so? Search google for lemon MB SUV models....Man those owners
are ****ED!

Larry - 1973 220D....simple, efficient, no electronics or computers.
--
Democracy is when two wolves and a sheep vote on who's for dinner.
Liberty is when the sheep has his own gun.

When I took over the management and maintenance of the 172 I used to fly,
the original turn coordinator installed in the panel in 1976 was still in
the plane. By the time I stopped flying five years later, we had put two
new ones in. Same design from the same company. Workmanship is as important
as design.

Much of the resdesign you talk about is intended to make workmanship less
important in the quality of the final product. It certainly does that. No
matter how good or bad the workmanship is, the product is still a piece of
crap!

--
Roger Long

Roger Long wrote:
Bob wrote:
But there are some folks that say "upgrade" to more modern model.

Modern isn't always better.
Roger Long

Hi, good point.
I had a conversation with a shop manager at my local GM (car) dealer.
My 1994 car toasted a
heater blower switch and had it replaced in 2000. It failed after 2 ½
years. I put in another one and it failed after 3 years. Each was
genuine GM parts from my genuine GM dealer.

The shop manager explained to me that engineers use computers now and
design more efficiently (insert wise crack here). These efficient
designs reduce the once common and expensive practice of over building
parts that contained wasted potential and added to unwanted weight and
increased costs. My response was, and reduced unit reliability! No
response from the shop manager.

I like to keep things simple. A rebuild and easy replacement sounds a
lot les frustrating than hoping for a similar foot print and all the
potential adapting. My motor lives under the sink in the middle of my
galley. I aint got but an inch any way around for clearance. Great for
engine access when I pull all the covers but I imagine a bear to make
something different fit.

But scheesh... when I sell the boat in 20 years who is going to buy a
boat with a 50 year old motor obviously with at leaser one rebuild?!?!

**** that statement is dumb, who is going to buy a 50 year old boat!?!?
Bob

Bob,

Your original post no longer shows up but I think from some responses I may
have missed the point that your engine is salt water cooled. If that is the
case, I would not rebuild it. My engine was run in fresh water till I
bought the boat so is probably worth an overhaul.

I was told at a boat show that the new Yanmars drop right into the same
space as the old ones. These are great engines and a new 3GM is probably
your best bet.

BTW more often than not when I'm advising someone on repowering a sailboat,
I'll find that they have a 3 cylinder engine but a prop that can only use
the horsepower of a 2 cylinder. You very well might be able to put in a
lighter and cheaper 2GM that would be happier running closer to its design
point and give you the same performance you have now. It wouldn't be quite
as smooth but the 2QM running a 2 blade prop in my boat is as smooth as I
could ask for. Fuel economy will also be slightly better taking the same
horsepower out of one less cylinder. The 2GM should fit easily on the same
beds as the 3GM with more room at one end.

I can give you a rough answer on this if you tell me:

Displacement
Length on Waterline

I can give you a better answer if you an also tell me:

Current HP and reduction gear ratio
Prop size, pitch' and number of blades
Propeller aperture size
C
Current max RPM and speed at that RPM

--
Roger Long

Roger Long wrote:
I can give you a rough answer on this if you tell me:

Displacement
Length on Waterline

I can give you a better answer if you an also tell me:

Current HP and reduction gear ratio
Prop size, pitch' and number of blades
Propeller aperture size
C
Current max RPM and speed at that RPM
Roger Long

Hi Roger:
Thanks for the reply. Yes, my QM is a raw water engine. I need to dig
out my manual for the Hurth-18 gear ratio. 2.37 may be the answer but I
need to check And this is another issue: I read the hurth18 was a
special model for the qm only. A rare pair with no parts availble. Seem
to remember a post about having to ceate a modifed flange and fit
another hurth gear on the QMs. My head hurts thinking about this.
Ill post the specs you requesed in a couple days. Thank you for
offering your time on this.
Bob

On Sun, 21 Jan 2007 09:27:42 -0500, "Roger Long"
wrote:

Your original post no longer shows up but I think from some responses I may
have missed the point that your engine is salt water cooled. If that is the
case, I would not rebuild it.

That's an excellent point, and I agree 100%.

You can not save a block with significant amounts of internal rust.