Gavin Scooters FAQ

Frequently Asked Questions

Which model of Gavin Scooter do you recommend for me?
How Do I Properly Balance the Scooter?
How Do I Vacuum Test / Pressure Test the Motor?
What does the Vacuum Hand Pump look like?
What Type of Batteries Should I Get?
Where I Can Go To Purchase Batteries?
How do I manage getting off the boat with my Gavin Scooter?
How do I properly rinse my scooter after diving in salt water?
What should I do if my scooter sticks on while I am diving?

Which model of Gavin Scooter do you recommend for me?

My personal recommendation on scooter choices here are the HDPE short for boat diving, the HDPE 26 a.h. for combination ocean/cave diving with one scooter, and the "standard" and "Magnum" PVC versions for long range cave diving. Any of these of course can be made into any size version, but if you know what your primary focus is, then start with the one that fits best, and get additional bodies and packs for the secondary uses.

How Do I Properly Balance the Scooter?

The best balance for the scooters is to have the batteries positioned in the center relative to the tube walls so that it has no bias. If you want a bias, make it so that your tow strap is on the area of the scooter that ends up on the bottom relative to gravity. This will allow the scooter to tow properly.

The fore and aft balance is best set so that the nose is slightly up when the scooter is hanging free. This will keep it up out of the silt , reef, wreck or other objects below you. It is great to have the scooter neutral, but keep in mind that the compression of the o-rings changes the buoyancy by about .7 pounds, so make the scooter that much positive at the surface, or neutral at the surface. You do not want the scooter floating up around you and tangling, unless you are diving a sensitive area like a reef where you might be catching lobsters, in which case positive will keep the scooter off of the coral. However, watch out and don't let it get behind you if it is positive.

Batteries are always slightly different in weight, the tube walls always have varying amounts of material in them, and different water has different buoyancy characteristics. For those reasons I make the tubes a little longer than they need to be, and I make the bulkheads such that there is room for spacers. The short pack makes no difference, so that one can be made without spaces and still have the nose up attitude, but the others may need different positioning of the spacers in the battery pack. Weight can be added to achieve exact balance.

The packs must end up 1/2 inch below the end of the tube. The lid should be able to fit onto the scooter snug to the tube with no o-ring. That way you know you have to correct positioning of the tube. You want the pack to hold the motor compartment shut tight (it has latches and double o-rings, but still needs to be held tight). You also want all of the stresses of the scooter to be distributed throughout , not concentrated in any one area.

I make the scooters to be a tad too light. I want them to float in salt water so if you do lose one, it will go to the surface and be recoverable. In cave, you may want to make it so that it is neutral at 10 feet and slightly neg at depth if there is an issue of it getting away, as in the Wakulla River, or neutral at depth if that is not an issue.

Don't make your scooter negative if you are boat diving, don't make it positive if you are cave diving with a resurgence.

How Do I Vacuum Test / Pressure Test the Motor?

The port plug opening is for vacuum testing or pressure testing.

Get a plug the same size and thread, bore it out and install a nipple in it for a hose to the vacuum pump, or purchase a premade plug or the whole kit from us (priced according to cost of the pump at the time.)

To test the vacuum, remove the hose from the special plug and screw the plug into the port in the motor compartment. Then re-attach the hose and pump it down to neg 15 inches in vacuum and it should hold indefinitely. If it does not hold, release the vacuum and move the hose to the pressure port on the pump. Then pressurize it and stick it underwater to see where the leak is, or spray liquid soap on the possible leak areas to find it.

If it is the plastic, send it back to us to be welded.
If it is the motor seal, replace it.
If it is the o-rings, replace them.
If it is the connections (which it never is unless you screw with them and do not put them back correctly), send that lid to us for redoing.

Any connections need to be held on both sides to tighten or they will back out of their threaded slots.

Images of Vacuum Hand Pump for Pressure Testing

Powersonic 33's for the long body and Yuasa 18's for the short body.

UPDATE !!!
For those of you who have the long bodied Gavins and are replacing batteries, be aware that Powersonic has changed the manufacturer of their 33 ah model, resulting in the batteries being 2 pounds heavier each. For fresh water, this will make the scooter negative.

The easy way around this is to use the Universal AGM 35 a.h. battery. It weighs what the Powersonics used to weigh and burns a little longer. The other solution, if you can not get those or if you want to use the heavier Powersonic or Panasonic batteries is to order a set of light PVC bulkheads from me. These are the same dimensions, only three pounds lighter per set. I normally use this bulkhead in one end of the fresh water version of the short body, in the 26 a.h. version of both scooters, and in the Magnum version to save weight since that one has five bulkheads.

The HDPE scooter is lighter and will accommodate the heavier batteries, so this is not a problem with that one.

I originally made the scooter too long to accommodate any battery changes, but they went a little too far this time. The HDPE uses the same body for interchangeability between tails, and you merely add a weight when switching between versions.

The Sears wheelchair charger is no longer available. I am trying out some new chargers made by Mako, but the old Interacter will do in a pinch, as will most any charger that accommodates gel batteries. The AGM batteries are a little easier to charge, so you can use the NAPA chargers for them as well. Any good marine charger will work for both types.

I am getting a bunch of light bulkheads run in case anyone is unable to get the lighter batteries. In Florida, it is no problem, but I don't know about availability in the rest of the world.

After testing some of the current batteries out there, it seems that the new and heavier Powersonic, Panasonic and Yuasa 33's have the same burn time as before, which is the same as the 32 a.h. Universals (the battery formerly known as a 33 a.h.) or the 35 AGM Universals.

A set of the new Powersonic, Panasonic, or Yuasas are 5 pounds heavier than before. There is one other 33 which is even heavier. Don't attempt to use these in the 25 1/2 inch bodies that you have now. Even with the lighter bulkheads and spacers they are still leaving the scooters slightly negative (for the standard PVC scooter, not the HDPE).

I am making the tubes for the PVC scooters longer for those who live in countries where the AGM batteries are not available, but for here, buy the AGM or anything in the 31-35 range that weighs 24 + - pounds.

One place you can get them from is:

For boat diving, what we usually do is put the scooter at the stern and have a mate hold it steady so it doesn't fall in, then get suited up and go to the stern, clip it to us, pick it up and jump in. If there is not a lot of current you can just have them hand it down to you. If you are diving a single tank it is really easy, if you have stage bottles and doubles it is best if there is someone to help a little.

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.

For more information about the damage that can be caused to your scooter fom not rinsing it properly after diving in salt water, refer to the Owners Manual section on Salt Water Diving.

If the scooter sticks on for real, as in if the reed switch breaks or the relay welds shut or mechanically sticks, you can stop the blades with your hand and turn the pitch back while you are changing stages or decompressing, and then stop it again and reset the pitch when you want to travel. With the oceanic clutch, this will mean replacing the clutch, a very inexpensive part. With the WKPP clutch, you can do this indefinitely.

If it is sticking on because the magnet is not coming all the way back, just pull the magnet back gently with your fingers. If the trigger is stuck, do the same and then free the trigger. Sometimes you need to check the trigger to be sure it is smooth on the outsides.

The other mechanism of sticking is on is when you get grit in-between the wheel and the leg. Then you need to loosen it so that it does not recur.

If the relay welds shut or mechanically sticks, there is a problem with the motor, so check with George before you ruin your relay.