The air pressure on my Pro Plus 2 Computer reads 300 lbs. low at start of dive and at end of dive. I used 2 other SPG's to do a comparison test. Is there a way to get the unit re-calibrated?

You should open the tank valve slowly if after opening i takes more than 3 seconds to get up to pressure something is not working properly. FOR SAFETY GAUGES ARE SUPPOSE TO BE FACING AWAY FROM U WHEN PRESSURIZING. IF GAUGE IS DEFECTIVE AIR PRESSURE CAN BLOW GAUGE LENS OUT FRONT OF GAUGE.

Hi Mike, never heard of that specific problem, maybe the pressure sensor is faulty. I would strongly recommend that you do not dive with this computer set up until you get it serviced/repaired as it may not be recording data correctly and will not be calculating your correct nitrogen build up.

60 lbs. is very very very low. was your cylinder scored at all. you may have siezed rings. on a two stroke, a leakage test (pressure test) will tell you if its leaking through the rings by air escaping through crankcase breather(listen through airbox) or head gasket which you would probably have already noticed. but honestly if you only have 60lbs, your problem will be very noticeable.

yes,

You need 3 things.
Compression
Good hot blue spark to all plugs.
Good gasoline and proper fuel pressure. 63-64 lbs.
If you have all 3 then move on to injector pulse to all injectors.
I think each injector is on a separate driver on that one.
Check for pulse to all of them.

You may be weak on fuel pressure . even a couple of lbs low on a cold start will cause a no start.
Double check cold start cranking fuel pressure. If under 63-62 lbs you have problems.
one test is to give it a squirt of carb cleaner not starting fluid. If it starts then you have a fuel pressure problem.
Run the full fuel pressure test and post back pressures.
Here is the guide lines on testing.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel. Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.

The 75-85 is only a check on the capable full pressure of fuel pump.
If you can not find the rubber return line check full pressure by plugging return line or just or the true full pressure can be taken direct at the end fuel filter.
What are the pressure readings that you have when done.
What are your cold start pressure readings?
Post back what you have. Good luck

You may be weak on fuel pressure . even a couple of lbs low on a cold start will cause a no start.
Double check cold start cranking fuel pressure. If under 63-62 lbs you have problems.
one test is to give it a squirt of carb cleaner not starting fluid. If it starts then you have a fuel pressure problem.
Run the full fuel pressure test and post back pressures.
Here is the guide lines on testing.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.

The 75-85 is only a check on the capable full pressure of fuel pump.
If you can not find the rubber return line check full pressure by plugging return line or just or the true full pressure can be taken direct at the end fuel filter.
What are the pressure readings that you have done.
What are your cold start pressure readings?
Post back what you have. Good Luck

You may be weak on fuel pressure . even a couple of lbs low on a cold start will cause a no start.
Double check cold start cranking fuel pressure. If under 63-62 lbs you have problems.
one test is to give it a squirt of carb cleaner not starting fluid. If it starts then you have a fuel pressure problem.
Run the full fuel pressure test and post back pressures.
Here is the guide lines on testing.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.

The 75-85 is only a check on the capable full pressure of fuel pump.
If you can not find the rubber return line check full pressure by plugging return line or just or the true full pressure can be taken direct at the end fuel filter.

What are the pressure readings that you have done. Good luck and hope the fuel pump is not a bad one you put in there, it's know to happen.

the gauge is bad

Scuba tanks can be filled well past 3200psi. When they do a hydrostatic test it is well beyond any pressure that any dive shop will fill a tank to. The highest I've seen the pressure get in my tank is 4000 and that is when the filler at the dive shop forgot about it.

Scuba gauges give a diver three very important pieces of information: 1. Time 2. Depth 3. Air Consumption This information enables a diver to stay within safe time and depth limits and avoid running out of air. There are many different devices on the market to help with this, from simple gauges to complex digital consoles. Time If a diver is not using a dive computer to monitor their nitrogen, they dive according to approved dive tables. To use dive tables properly, a diver needs to track their downtime. This can be done with a good dive watch. Two things make a good dive watch: water resistance and a rotating bezel. 1. Water Resistance. Good dive watches are rated to a depth in meters or feet (e.g. 200 feet) or a pressure rating in atmospheres (e.g. 4atm). Even though most divers probably won’t dive below 130 feet (the recreational dive limit), a good dive watch should be rated to 200 feet. Note: There is a difference between “water resistance” and “waterproof”. A “waterproof” watch is what you would wear in the shower, but would probably start leaking at 15-20 feet. 2. Rotating Bezel. A bezel is an adjustable ring on the face of the dive watch with a pointer indicator. At the beginning of a dive, the pointer on the bezel is aligned with the minute hand where it stays though out the dive. At the end of the dive, you compare the difference between the bezel and the minute hand to find out the length of the dive. The bezel should only move “counterclockwise”. It is possible to accidently move the bezel during a dive. Because of this, watchmakers make sure any accidental movement will turn the time in a conservative direction, making the dive longer rather than shorter. Depth Another important part of scuba gauges is a depth gauge. A depth gauge enables a diver to keep track of their depth even if they cannot see the water’s surface. Gauges can be either an analog (needle-and-dial) device or a digital device. Both work in the same way. They measure the surrounding water pressure and convert this into an accurate reading of your depth. Another feature of a good depth gauge is a maximum depth indicator. This tells a diver their maximum during a dive and must be reset after each dive. Air Consumption Another equally important part of scuba gauges is a submersible pressure gauge (SPG). This is connected to the first stage with a high-pressure hose and measures the pressure of the air in the tank. The SPG is much like the gas gauge on a car. At the beginning of a dive, a diver starts with a full tank. This should be about 3000 psi or 200 bars. As the diver breathes during the dive, the gauge will move slowly downwards. This allows the diver to have enough air left in the tank to: 1. Make a slow, safe ascent 2. Make any necessary decompression stops 3. Inflate their BCD once at the surface 4. Breath from the regulator if the surface conditions are rough A submersible pressure gauge also allows a diver to stop diving with air still in the tank. This keeps contaminants from entering the tank due to no air pressure. Wrist Depth Gauge Scuba gauges come in two basic styles. Stand alone gauges or gauge consoles. Stand alone gauges such as a wrist mounted depth gauge or a submersible pressure gauge attached to the first stage of a regulator are great backups when using digital gauges. Gauge consoles allow divers to have all their gauges in one place. Although less easy to read, analog gauges sometimes give slightly more accurate readings than digital gauges, particularly at shallow depth. Submersible Pressure Gauge Choosing Scuba Gauges When choosing scuba gauges, remember to look for: 1. Easy-to-read numbers 2. Luminescent dial or back lighting options 3. Rotating/swivel mounting 4. Easy disassembly for cleaning or replacing parts 5. Good warranty