Owner`s Manual - Gavin Scooters

Owner`s Manual - Gavin Scooters
Owner's Manual
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Access Port Plug
Nose O-Rings
O-Rings - Motor Compartment
Battery Charging
Reed Switch
Battery Connections
Battery Packs
Riding the Scooter - Body Position
Salt Water Diving
Body O-Rings
Seal and Clutch Assembly
Switch Connectors
Tow Cord
Motor Connections
Trigger Cable
Trigger Pins
The Gavin needs little or no maintenance (either version), but there are certain
things that should be checked periodically. We highly recommend that you read and
understand this manual fully to ensure the proper functionality, performance and
longevity of your Gavin scooter.
When all is well with your Gavin Scooter, the motor should NEVER get hot, it should
never leak through the seal, and it should never need any kind of servicing
whatsoever. These are continuous duty electric motors and are highly efficient.
Any and all questions on your Gavin Scooter should be directed to George Irvine.
George has extensive experience and makes use of that knowledge base. What takes
him seconds to figure out and minutes to fix, could take the uninitiated days. He also
likes to see how they are doing from time to time and can easily spot developing
problems and correct them. He has all the parts and special tools to perform any
type of job on these, and he likes doing it.
Access Port Plug
Be sure the access port plug is all the way down before use, or it could leak
hydrogen. If the fittings get disturbed for some reason, they could back out of their
threaded slots slightly and leak. This has not yet happened, but some people must
tinker with things, so be aware that these are threaded through the lid and must be
held firm from the top when tightening the bolts.
Batteries can be quite frustrating. They will test perfectly and then fail for no
apparent reason. They can not tolerate heat. Do not store them in your car or in a
hot place. 110 degrees F is all it takes to kill them. They otherwise should get 200
cycles, but we throw ours away after less than 100, or if the burn test falls more
than 5 minutes short of optimal.
If you get bad ones from us, we can have our supplier ship new ones right to you.
It's best to get them locally so you can take them in and exchange them. This saves
weight in shipping, which costs more and may damage the scooter.
The other thing to remember is that all batteries off gas - even Ni-Cads. Never leave
your scooter sealed or pull the trigger out of the water. If you leave it sealed, it may
blow up and that can be extremely dangerous and cause serious injury.
Battery Charging
You will need a 24V Battery Charger to charge your scooter batteries. Sears has one
with 12 and 25 volt settings, gel cell settings, fast, normal or maintain charge
settings, an analog ammeter, 2,10 or 20 max amp settings, etc., and it is in a proper
case for good ventilation and costs about $80 in the automotive section. The
Interactor charger does not offer settings, therefore allowing no control of the charge
process, and is overpriced at $110. Xenotronics has a high quality charger for about
$400, but the Sears charger is more than adequate.
With the Sears charger, you must be sure the "gel" switch setting is in the right
place or it will put out too much and give you all kinds of bad signals, not to mention
improper charging.
They also give bad signals if the connection is not perfect. Make sure your charging
port plugs are not getting loose or oxidized.
Brownies has some chargers they found that seem to work. We ordered one but
have not tried it.
To check to see if the batteries are charged if you are not sure that the charger is
telling the truth, put your multimeter on amp dc and move the non com plug to the
amp slot and then clip it in between one side of the circuit (you will need to jumper
the other side) and turn on the charger. If it will not take current and the charger is
reading voltage, then it is charged. You can check the charger for volts first and then
the battery, then the amps, and then the resting voltage of the battery.
Battery Connections
The connections from the battery are gold and should never cause a problem. They
are two-part connectors that hold the fitting without pulling the wire - use the
handplugs to disconnect. Inside they have set screws holding the wire, which is
tinned with silver to go against the gold fitting. At the other ends are merely high
temp connectors, crimped and soldered. The charging port is a simple Radio Shack
connector. The wire is all boat cable, #10.
Battery Packs
The battery packs need to have their bulkheads spaced properly. The upper bulkhead
needs to be such that the lid can go all the way down without the O-ring. The nose
cone has inserts in it to hold the top of the battery rods in position so the pack will
not move. You can put a piece of foam in there as well. We do that to keep pressure
on the nose cone when the O-ring is out. See the FAQ page for more information on
balancing your scooter and battery packs and spacing.
The blades will eventually wear out and the scooter slow down a little. This is
because the holes that are used to control the pitch wallow out. New blades are 27
per set. It takes a while to wear them out. I have not personally worn any out, but
my hard core divers have. If there is any other change in performance, sound, or
speed, send us the motor immediately, without passing "go". It is either perfect, or it
is not. If not, we fix it.
Body O-Rings
The body O-rings are number 375. They sometimes appear "cracked" on the outside
- ignore this. You may never have to replace these, but they cost about a buck if you
We have been testing clutches and have found that there is no set number of
washers that work for any given combination of Arnold Jackson clutch and motor.
The shafts are different on different motors. The step in the clutches is different for
different clutches. What has to be done is that you have to add enough washers to
clear to top of the shaft, but just barely. The clutch needs to slip easily; it needs to
slip as soon as it touches anything but water. There is no number of thick washers
that will work. You can check the thickness of the washers with a micrometer. They
need to be .024. The .032 washers are too stiff. Just one too many washers will not
allow the clutch to slip. The .032 are for the Mako clutch, which slips far more easily
and will wear out upon repeated slippage, whereas the Arnold Jackson clutch is
designed to slip any number of times. The replacement Mako clutch costs about 4
bucks. The replacement Arnold Jackson clutch costs about $120.
You must first check this on the bench with the relay bypassed or it will fry the relay
if the clutch does not slip.
1. Open the lid
2. Disconnect the positive lead from the motor to the relay, jumper that leads to
the battery.
3. Put a jumper on the gold pin in the black socket on the motor compartment
4. Hold the prop and touch the black jumper to the battery.
It should slip instantly. If it grabs, start removing washers until it does not
If you are a weenie, and if you have one of my rewinds, you are not going to
like it if it does not slip - consider yourself warned!
If it does slip properly, or after you have put the washers so that it slips
properly, you are now safe to put it back together and put it in the water to
test again.
5. Make sure it will hold with full pitch and with fully charged batteries.
Grab it underwater and make it slip and be sure it will re-catch.
Sometimes it will ride on top of the plate and you just bump the trigger a couple of
times to get it to reseat. I keep mine so that they nearly slip all the time, and
anything that got into the prop, like cave line, would instantly slip the clutch. To give
you and idea of how it should be set, you should be able to stick any body part in
there with no worries. The Mako needs to be kept more tight and not slipped
Do not add back in more than one washer at a time or you will lock it up and fry it.
The other thing that happens, and this happened to me, is that if you stall the motor
just right, it will arc on the brushboard and then the whole motor needs to be taken
apart. To avoid this disaster, do your first testing on the bench where just touching
the lead to the battery momentarily is all you do the first time. I was trying to see
what would break and I found out. It was interesting when I took the motor apart - it
was dated 1988. It took me 14 years to have to take it apart.
If you do not have the right washers, you need to get them from Arnold Jackson, or
otherwise all of you get together and designate somebody to order them and
distribute them, or get them from whomever you got the Arnold Jackson clutch from.
While you are at it, throw away the Arnold Jackson screws and put in 8-32 1 1/4"
pan head Phillips screws.
The latches are sometimes difficult or time consuming to get made, so don't break
them. If you do break them, however, George Irvine will send you more. Leave the
latches closed as the only time they like to break off or rip out is when they are
open. Closed, the strikes will straighten out before you can sheer those screws, even
in the PVC body. If you mess up the latch holes, you can drill them all the way
through and use a 3/8" ## 6-32 machine screw and some silicone to hold you over
until a new body can be made. Bill Gavin used to run them through like that, but it is
not necessary for strength, and leaves open that quick fix option if you do mangle
one. The other option for quick fix is to hot air melt the PVC and put the screw back
in. That can also be done with the HDPE parts. If you do mangle any part, like if you
wreck your car or something, send it in to be welded back together - either version.
Motor Connections
When checking connections under the motor lid, be sure to not try to tighten them
without holding both sides of the fitting (remember they are threaded, and
tightening the gold nuts will turn the gold fitting the other way unless held.) Make
sure these fittings are tight so there is no intermittence in the scooter. If there is,
this is the problem.
Learn how to use a multimeter. Get one from Radio Shack (if you don't have one,
don't tell anyone because that falls into the "too stupid to dive" category). I am sure
you have all seen Pina checking her backup lights with one before every dive, along
with her primary light and her scooter. The continuity function will tell you if your
reed switch is working, the ohms will tell you if your relay is welded, the amps will
tell you if you motor is drawing the right amount of current and hence has no
problems, and the volts... you guessed it, will tell you the resting voltage of your
batteries which you will know is what it should be or not. We need to not be sending
me back scooters that need a two dollar part. We need to find out what is really
wrong and then figure out what to do about it.
If the relay mechanically sticks, well that is an odd one. If it fries in the on position,
this means it took a severe current shock and that means the motor is broken. Do
not keep replacing it and blowing it. Check it with the meter - relay for ohms, motor
for current, etc. If it the thing just won't work, we get out the meter and start with
the reed. Then check the relay, (which you can hear click) and then apply current
directly to the motor. If the motor won't run, it needs to be rebuilt. It lost its brush
board or the wires to it. If the relay clicks, the motor will run, but not through the
relay, there is a broken solder joint and you must re-solder the five points on the
back of the board. If the relay won't click or is stuck on but the reed and motor are
ok, then the relay needs to be replaced. De-solder it from the board and replace it.
The reed comes from any Radio Shack, the relay from any electronics place.
Nose O-Ring
The nose o-ring should be left out when not in use to reduce risk of hydrogen buildup
if the batteries offgas. The ring should not be put in within an hour of charging.
When you get out of the water, take out the ring. What happens is that if hydrogen
comes out of the battery through its vents, as it does when charging or really at any
time it wants to where the reaction gets behind, it builds pressure in the sealed
scooter and could possible find its way past the double O-ring seal on the motor
compartment lid.
O-Rings - Motor Compartment
The O-rings in the motor compartment are numbers 252 and 256 for the HDPE and
252 and 256 for the PVC version, or both can be 256 on the PVC version for a tighter
fit for the double seal. These are the only rings you should ever grease (silicone - but
do not use spray or hydrocarbon sprays as the propellant could ignite later when you
start the motor), but the main thing is to be sure the O-rings are "alive" and not
"dead" (not flat or losing their resilience). and that there is nothing on them that
would cause them to leak.
Be sure the lid is all the way down before use. When putting the lid on, it must go
down evenly and not extrude the ring anyplace - you must feel no springing action at
all. It is easier to get it all the way down if you remove the port plug first, and then
put the plug back in after the lid is secure. On the HDPE version, the fit is even
tighter so it is harder to get the lid in all the way. This is critical, so be sure it is in
and sealed.
You should periodically check this compartment with a vacuum hand pump to be
sure of its integrity. You should remove the access port plug after dives and hold the
tail upside down to check for water and to observe any other problems. The motor
should NEVER get hot. If it does, there is a problem. If the motor gets hot, it will
expand the air and push the lid off. To help ensure that the motor does not get hot,
observe the following:
DO NOT spray any conductive lubricant into the motor
DO - Dive a streamlined gear configuration and maintain proper body position
to keep from giving the scooter too much drag for the prop setting.
Check the motor temperature from time to time when using the scooter by touching
the tail cone. If there is a problem, send in the motor. Do not run it into the dirt. Do
not get lazy and blow these things up. Do not leave the nose O-ring in when not in
use, transporting or otherwise after use and never seal it after charging without
waiting at least 30 minutes to an hour.
To check the compartment for water after diving, it is best to merely remove the
testing port and check for water, instead of removing the lid. Every time you remove
the lid, it stresses all the connections unnecessarily. If you do remove the lid, be
sure to keep one hand on top of the motor compartment lid when releasing the
snaps. The lid that has the relay under it. If you allow the lid to pop up it will pull on
the wires from the motor.
Reed Switch
The reed switch may be one of two types but we usually choose the Radio Shack
window switch because it is widely available in most countries, even though there is
no reason for one to break unless you bang it on something with the scooter apart. If
you do replace it, use the same fittings and be sure to sand off the little flange so it
will fit in its hole. The other type of reed switch is one that is threaded into the tail
section. This type of reed switch you must get from me, but that is no problem. This
one lets you adjust the trigger by turning the reed.
The relay is a 30 amp relay on a custom-made board. For replacements, either get
them from me in one piece or de-solder the relay and put on one just like it - the
part number is on the relay. Some relays are just faulty and can mechanically stick,
but usually if there is a relay problem it is really a motor problem that needs to be
fixed. Any motor problems need to be sent to George Irvine for repair or
replacement at no cost. Just take out the motor by removing the four screws and
send it to us in a double box that is well padded so the tail cone does not get
Riding the Scooter - Body Position
The body should be held in a flat position with the neck tilted back to see and the
feet at body level or higher. If you are at any angle, you are inefficient and will be
slower. If your feet are pointed down, you will be much slower and under
unnecessary stress. You should be able to operate and steer the scooter with one
finger if it and you are properly balanced and positioned. JJ and I ride these things
for 6-7 hours straight with no fatigue of any kind. That is what you are shooting for
no matter how long your dive is. You should never be fighting the scooter, and
length makes no difference. Pina rides a Magnum Gavin in Manatee with no problem
what so ever, and she is 5'3", 110.
Improper riding of the scooter merely makes it draw too much current. My motors
are set to 57 pounds thrust with a static draw of 16 amps (that is what the burn
times are based on and the battery condition tests (see the WKPP page for burn
testing details). If you are a good diver, you should draw a lot less than 16 amps.
Speed adjustments allow the team to all move together.
Salt Water Diving
Any scooter used in salt water needs to be rinsed in fresh water afterwards. Don't let
it sit, as the salt water will leave salt crystals which will then react with the metal
parts and get into the surface of the motor seal. The way a seal works is by a
molecule layer of water across its face, not because the material has some magic
properties. We use ceramic seals which will not rust, but will be scored if left with
salt on them or around them. To break in these seals and start the process, we use a
drop of motor oil, but once the scooter is put together, it is not a good idea to
disturb this device.
A rinse in fresh water after diving, followed by a spray of CRC or WD40 around the
area of the seal, will do a lot to prevent any problems. You do not have to take the
props and clutch off, merely use the little tube that comes with these cans to spray
under the clutch and into that area. The idea is to prevent the cone around the seal
from reacting with the salt and eating away. Eventually this process will leave the
seal unable to hold at its edges, even if the two seal plates are not damaged. Then
the whole motor cone has to be replaced, which is extremely time consuming.
An easy way to rinse a scooter is to put it in a fill bin and run it a few seconds (with
the pitch turned down). You can also use a hose and force water in under the clutch.
Most of the snap rings are stainless steel, but even that will rust out and let the seal
spring loose, which will push back the clutch plate from the shear pin and allow the
whole prop assembly to unscrew. Once in a while that ring needs to be replaced. It is
just under the clutch plate. The snap ring under the seal is hard steel. That ring
needs to be in place or the shaft will have play in it, causing the seal to leak when
you first put the scooter in the water. There should be no play in your shaft; if there
is, that ring needs to be replaced, which means removing the seal all the way. The
bottom part comes out with an O-ring pick - this does not hurt it at all. Check your
prop set before putting the scooter in the water and push the whole thing inward to
be sure the seal is shut. Otherwise they will leak a little when you first put them in
before the pressure closes the seal. That is where all the leaks actually happen right at the surface when you first put them in the water.
Seal and Clutch Assembly
The exploded diagram of the drive train shows the correct sequence of clutch washers. In
the WKPP clutch, there are three matched sets and the one facing down at the ring on the
bottom. With the Mako clutch there are four sets plus the one facing down.
The seal is easy to replace. Remove it with channel locks, remove the inner donut with an
o-ring pick. The snap ring is under the inner donut. There must be no play in the shaft.
Check and be sure that the ring is in place. It is steel, not stainless, since it needs to be as
hard as possible. Place the new donut into the hole without any kind of silicone or
lubricant. Spray the bell side of the seal with lubricant. Put a drop of motor oil on the
donut. Slide the bell down and then press the rubber ring down all around with a flat
bladed screwdriver. Then add the spring, cap and stainless snap ring. Run the motor for a
couple of minutes to break in the seal.
You do not need to take the motor out of the scooter to replace the seal.
Switch Connectors
These small "banana connectors" need to be kept splayed out or they will not have
as good a connection or hold as well. This also needs to be done to the HID light
banana connectors or they will get intermittent.
Things come apart, screws back out and so forth, due to vibration from a misaligned
vehicle or from a boat with a bent shaft or misaligned motor, which is 99% of the
scows they use as dive boats. I never personally have this problem, but I see it from
some of you. If the scooters vibrate too much in transport, the big bananas may
come apart, but they don't unplug as they are held down by the lower bulkhead
being too close to them for them to unplug by themselves.
I also have something that is not apparent in the photos that some of you may want
to use on your scooters. I put a short piece of clear tubing over the banana
connectors. You have to unscrew them, then unscrew the inside, slide the hose on
and then the back and then the inside and screw it all back together. The hose
should be slightly curved and just barely reach the level of the lid spacer. The wires
then go through the normal access hole. This makes it impossible for the bananas to
come unplugged.
Tow Cord
A proper tow cord length is a must with these scooters, as well as the positioning of
the length of the two sides. Also it is suggested that you have DIR gear configuration
if you want to get the most speed, use the least current, and be the most efficient.
The length of the tow cord must be such that the scooter is as far out in front of the
diver as possible and the diver's right hand is merely relaxed on the right handle,
and so that the left hand can easily reach the shroud. This will allow the full effect of
the scooter breaking the water and crating a "shield" around him so that the stages
and such do not add significantly to drag if rigged and carried in the DIR prescribed
method. This positioning will also prevent the scooter from 'reverse thrusting"
against any part of the diver. If you can feel the prop wash, you are riding the
scooter improperly.
For tight areas, you may want the scooter in a little closer, in which case you can
take a wrap around each handle, or make your cord shorter by the length of a
double ender and just add or remove the double ender as needed by clipping into the
double ender or just the main clip without even removing the double ender. This way
you can "shift gears" for changing conditions. Most of the time, you will want the
scooter as far out in front as is comfortable. If you are new to scootering you may
find that you feel more comfortable in the beginning with the scooter closer to you,
but you should strive to keep it out as far as possible. Once you are more
comfortable riding it, you will not want it in close anyway as this does not allow you
to relax the way you can with it outstretched.
Trigger Cable
To replace or change the trigger cable, take the wheel off and screw on a new ends
section of wire, thread it through the handle, and then put the wheel back but
tighten the nut so that it stays in the "on" position while you crimp the cable with the
trigger in the depressed position and then loosen the lock nut again. For the tapered
version , leave it in the "off" position and crimp it with the trigger all the way out
(that one has a bolt threaded through the leg which does not allow you to tighten
past the optimal point.)
Usually , the way you break the cable is by catching the magnet on something while
transporting the scooter. I try to keep that magnet at about the edge of the tail so it
does not stick out. I also watch that when carrying and do not use that leg as a
handle. With some of them , and more so with the tapered version, I have reversed
the direction of the magnet so you are pulling it from inside to out to prevent this.
However, it is then harder to operate if broken.
If the trigger cable jumps or breaks during a dive, you may operate the
scooter from the wheel by resting your right hand on the shroud strut and holding
the magnet in place with your thumb or index finger with no change in riding stature.
Trigger Pins
Trigger pins are just standard boat trailer hitch pins and can be found at any
hardware store or marine supply store. The scooter should always be pinned when
not in use. When towing, staging, or leaving a scooter on the line, pin the trigger and
turn the pitch of the blades to zero (by turning the knob at the blades counter
clockwise.) It is a good idea to have a few spare trigger pins and keep one on the
tow cord.
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