Phantman wrote:
I've always wondered why the designers
didn't just get the cooling water through the bottom of the boat
like
any normal straight inboard setup.

Jim wrote:
I suspect that the engineers felt it
unnecessary to reinvent a proven design

JamesGangNC wrote:
The inside water pumps are basically the same design rubber vaned
pumps. All of them will self prime if needed and the distance is not
far.

Jim wrote:
I don't think the internal pumps are self priming. I would consider
changing
my mind on that if I could see some proof.

Phantman wrote:
Are you familiar with inboards? I don't mean sterndrives. I mean
proven design straight inboards that have been around since long
before sterndrives were dreamed up (and still common everywhere). They
get their raw water through the boat's bottom via a thru hull fitting.
Whether or not they use a standard automotive pump or a special marine
design that's self priming, I'm not sure. But whatever it is, it sure
looks like a standard auto water pump and bolts right into place.

Jim wrote:
Rick, the pump under discussion is the raw water pump that brings water
into the boat, not the circulating pump.

Phantman wrote:
Well, lets get on the same page then. My question was, "why wouldn't
the designer of a sterndrive use the same less complex method of
cooling water intake that Inboards have always used (and still use).
It's a time tested and proven design, no hauling the boat for impeller
maintenance, and less expensive to build. I see no advantage to their
more complex, more difficult to maintain design. That's not to say it
doesn't work at all, obviously it does. But it's one of several
complexities of standard sterndrive design that could easily be
simplified imho.

Jim wrote:
Who knows why they designed the IO the way they did. I don't know if it's
more complex. The main difference is the IO makes 2 90 degree power train
turns vs the outboards 1 turn.
Cheaper to build, maybe? Less work and expense for the boat builder(no
bronze thru hull, screen, hoses, sea strainer, etc.)
How would you simplify the design of the IO?

Most importantly, I would eliminate the boots. All of them. Which
means I would have to start over from scratch with a design. This
forum probably isn't the place to get into that. But eliminating the
outboard impeller and transom intake system would be a step in the
right direction as far as I can tell. I've asked this same question
of mechanics, engineers and some fairly knowledgable people, but so
far I haven't found anyone that can explain why the outboard impeller
is a better idea. I'm sure I'm not the only one who's thought about it
though, including whoever designed the I/O in the first place. I wish
I knew what he was thinkin'.

Rick