"Matt Lang" wrote in message
om...
Guys,
I am thinking about getting a harbercraft jetboat ... these things are
made from aluminum and have the 175 HP Mercury sportjet..
So far so good ... Now what raises the fuel warning flag are the
terms:
- jet
- 2 stroke
- carburator (two of them 
The boat will burn about 5 gallons per hour at 30 mph... now I was
wondering how this compares to a similar sized fiberglass hboat with
115-150 HP 4 Stroke outboard..
What is the fuel you burn at cruise speed and WOT, whats your boat
size/weight and what motor are you running ..
I am interested in how the relatively light alu jetboat compares to a
more conventional boat with 4 stroke motor..
Any info is appreciated 
Matt
Matt: I'm fairly familiar with the Harborcraft hulls, the old Jetcraft
hulls and the sportjet.
First, as someone pointed out, Harbaorcraft bought out Jetcraft - and pretty
much changed all the lines to the Harborcraft hulls, whether they be labeled
Jetcraft or Harborcraft. The new Jetcrafts are really nothing like the old
ones, and they are exactly like the Harborcrafts. Not to say
Harborcraft/jetcraft aren't decent enough hulls - they are very fine hulls.
But, they're not of the Grade A+++, bulletproof build quality of the old
Jetcraft. And you're not paying that kind of money either, probably.
Just mho, of course. AND, this isn't your question anyway!
the Merc 175 carbeurated sportjet. I've spent a lot of time with my
friend's and have gone on a very long trip with him as well as many short
ones. Where are you getting the 5 GPH at 30 mph stat? Product literature
(propaganda) or actual experience? Our experience, with a hull that's a bit
lighter than any Harborcraft hull I've seen is more like 10 GPH at cruising
speed which indeed is around 30mph (with over 40 at wot). About 3 miles
per gallon, rule of thumb. Which, by the way, is excellent mileage for a 2
stroke jet. With a comparable large outboard jet on a boat of any size, one
is lucky to get 2 - 2.5 miles per gallon at that speed/rpms, so we've always
figured the sportjet is a good 30-50% better - and this is measured, not
manufacturer's info.
Your mileage estimation at 5 gph would be 6 mpg, which would be
unbelievable for any jet boat with a large V6 two stroke - and about double
what an inboard Chevy-based jet would get (which are generally considered to
be quite a bit more fuel efficient than any two stroke jet) - which
indicates to me how far fetched it is. My 90s era carbeurated Chevy 5.7 L
inboard jet (on an old Jetcraft, by the way) burned 8-10 gph at cruising
(around 30 mph) speed; anything under 10 gph was considered pretty good for
that speed.
By the way, the info my friend received in the sales brochure for his boat
also said 5 mpg at that speed and it's just not proven to be true.
That said, I really think the Merc sport jet line is a great option for a
jet boat. In my opinion, the Merc. sport jet is BY FAR the most efficient 2
stroke carbeureated jet - far more efficient than a comparably powered
outboard jet. I would assume the 200 hp Optimax is even more efficient. I
like them a lot and wouldn't hesitate to recommend them. I definitely like
them better than any outboard jet option because of the efficiency and a lot
more than any chevy-based jet because they're so much lighter and take up
less interior space.
And don't get me wrong - there's absolutely nothing wrong with the
Harborcraft. It's a fine fairly light weight and good value in a hull.
In other words, even though I disagree with your mileage estimate, this
sounds like a great, good valued rig to me, based on what I've seen of the
hulls and what I know of the motors.
Hope this helps.
Cam