Ok, I've seen a few people ask about outboard jets from time to time.
Conversions, oem, used, etc. I'm not sure were to post this, but some folks
might find it useful.

Basically there are two types I have found in my research. There is a safety
jet that looks like its for Johnson Evrinrude only that I see for sale on
Ebay periodically. It looks like it hangs down just as far as a regular
outboard and has no real low water gains except may reduced likely hood to
damage the drive when hitting things.

The other, and the one most folks are familiar with is made by Specialty
Manufacturing in San Leandro California. I could not find ANY other
manufacturers. Also, used ones are almost impossible to find. I guess that
means they last atleast as long as the boat if properly cared for. I know I
have been looking for about a year and have seen very few used jets
available anywhere.

They aren't cheap. I recently ate a rock on my little Mercury 50 ELPTO. I
bent a prop shaft, twisted the drive shaft, and munched the stainless steel
prop that was on it. A rebuilt lower unit and repairing the prop added up to
about 1300 dollars. A brand new jet pump from Specialty Manufacturing is a
little over 1600.

I bought the jet. It took me just under 5 hours total to assemble it and put
it on my outboard including the time to unbolt the motor and raise it to the
highest possible mounting hole and raise the jack plate as far as it will
go.

I test ran it this afternoon. It performed about as expected except for a
couple things. It over revs. No I don't mean because its cavitating or
anything. The impellor simpley does not put enough load on the motor to keep
it down at its redline at WOT. It will run almost 800 RPM too high.

With the prop lower unit I got speeds of around 34 MPH pretty consistantly.
At WOT the jet unit pushed the boat upto about 26 MPH and might have gone
faster, but I backed it off because I didn't want to blow a motor. Thats
pretty much in line for power output as I expected. The say 30% loss in
output power and about 80% loss in top speed. However, I can't use all that
power since it now over revs. At the rated 5500 RPM the boat is scooting
along at just under 20 MPH.

There are some issues I still need to resolve as far as setup.

Since I have a jack plate on the boat the motor sits too far behind the
boat. I'm not sure how much afffect this has, but the jet really needs a
smooth stream of water off the back of the boat. Further back I may not be
getting a smooth stream. The suggested solution is to weld or screw an
extension plate to the back of the boat.

The boat is a flat bottom jon, so it may be causing the jet to ingest some
extra air. Some creative shapping of the plate mentioned in the previous
item might help the air bubbles shed off to the sides.

Even with the jack all the way up and the motor mounted in the highest
possible mounting hole I was not able to ge the motor as high as the
manufacturer reccomends as your starting point. The only option I have left
is to use something else or raise the jack plate on the boat. I will have to
drill holes in the jack plate in order to raise it any higher.

There is a little more service required for a jet. Checking clearance and
repositioning shims periodically. (probably once a year) Forcing grease into
the impellor shaft bearing every trip (8 to 10 hours of operation). A little
extra grease to check for water about every 40 hours of operation. Replacing
the water pump impellor is going to be a little more work also. You have to
remove the pickup housing, and jet impellor to get to some of the bolts to
drop the jet lower unit.

I have not done any shallow water running, but I did run over a patch of
pencil tulies. It sucked some in and immediatley quit pushing hard. Oops. No
way to get around to clear it from the boat. You will have to pull it
alongside a dock or get in the water behind the boat to clear any clogging
vegation from the pump.

That's about it so far.


--
Bob La Londe
Fishing Arizona & The Colorado River
Fishing Forums & Contests
http://www.YumaBassMan.com



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