Porthole screens

All portholes on Colorado Cowboy (GH37 fka Lo Que Se A) have screens glued onto an exterior retainer ring.  I  can’t find any manufacturuer info on the portholes flanges and haven’t wanted to take one apart to investigate further.  Anyone know  who manufactured these portholes and if new screens are available,  or were the screens a later add on?

Hauling and Blocking a Great Harbour 47

Hauling and Blocking a Great Harbour 47

Disclaimer – this has been written by Henry Dennig from comments I have collected from various owners.  I do not have any engineering background.  I would recommend anyone having their boat hauled and blocked, should discuss this event with Ken Fickett before having it done.  If you have any suggestions or comments on this post, please let me know – hjd




When hauling a Great Harbour 47, the slings should be aligned with the internal structural walls.   The aft lifting point is salon/engine room wall, which is forward of the salon windows, and before the port light.

The forward lifting point is the forward berth wall.   Directly forward of the bathroom / office port light.  Below the pilot house doors.

Ideally the boat should be lifted with four lifting straps to spread the weight but can be lifted with a travel lift using two straps.

The boat does not have stabilizers, nor spray rails.



The Great Harbour 47 does NOT have a keel.  The weight of the boat must be supported around the edge of the boat.   Each side of the boat should have five blocks/jack stands.  If jack stands are used, they must be chained.

A blocking under the transom and bow can be done after the sides are supported.


Photos of past hauling and blocking




Preferred lifting with four straps

Forward Straps


Forward Slings

Forward strap at the front of pilot house

Rear strap in front of ladder door

Aft Straps

Aft Slings

Front strap in front of salon window

Rear strap in front of engine exhaust


Bow thruster battery bank

Our bow thruster battery bank consists of two 12 volt AGM
start/deep-cycle batteries. Monitoring the charge state of the these
batteries under the bed is a pain in the neck. To ease the problem, I
recently made and installed a battery monitor such that the voltage
and charging current of each battery quickly can be monitored without
taking the mattress and hatch covers off. If anyone is interested in
installing one of these please contact me for details.

A related issue was the negative terminal on the port battery. This
terminal suffered a partial meltdown due to a loose connection in July
2010.  A repair allowed continued operation without battery
replacement. Unfortunately, during installation of the battery
monitor, a crack was observed across the face of the terminal. When I
wiggled it, the terminal broke off nearly flush with the top of the
case. Although the battery is old, considering the cost of a new
battery, a repair attempt seemed worthwhile. The repair worked – a new
terminal was successfully cast onto the old terminal stub. A load test
with the bow thruster confirmed that operation of the new terminal
under heavy load current is satisfactory. Please contact me if you
need details on the battery terminal repair procedure.

John Reynolds

Port Battery Terminal Batt Terminal Battery Monitor


Before doing any maintenance, if possible flush water through the systems before working on them.  Then turn the head/toilet breaker switches to OFF.

Maintenance on head/toilet vacuum generator.  These are located below the floor in the crawlspaces accessed by hatches – one hatch in the galley for the port side (master stateroom) head, and one hatch in the guest stateroom doorway for the starboard side (guest) head.

Replacing duck bill valves.  These are one way rubber valves – four per unit – 2 each on each side of the inlet and outlet pipes connected to the vacuum generator pump.  Should be checked on a regular basis once every couple of years – or more often if using the boat full time.  Need eight duck bill spares for a complete change to both head units.  Note that these duck bill valves come in different diameters so be sure to get the right size (1 ½ “) when purchasing them. (Note: newer GH’s have larger sized valves)

The easiest way to replace these duck bill valves is to remove the complete generator and take it out on the dock where you can more easily remove/unscrew the plastic pipes containing the duck bill valves, located on either side of the generator pump housing.  (see owner’s manual) Doing it while in the crawl space is not impossible, but you need to be a circus contortionist or at the very least slightly crazy to attempt it.  Come to think of it, you have to be slightly crazy to attempt this whole operation anyway.   And if you don’t look at the whole world slightly different after you’ve done this job, then you will afterwards.  Trust me on this.

The starboard side vacuum tank generator is easily removed by removing the two bolts holding the unit to it’s support bracket on the floor of the crawlspace.  Then the unit can be moved sideways from the inside two bolts holding it down.  Leave the two inside bolts alone and only remove the two outside bolts – that are easily accessible.

To remove the generator you must first remove:

a.) both sanitary hoses- input from the head side and output from the holding tank side, by loosening stainless steel hose clamps, and twisting the hoses off the plastic pipes.  Watch out for yukkie stuff coming out the hoses when you remove them.  Have a bucket and clean up rags to clean up any spillage.

When removing the sanitary hoses, you have to slacken off the stainless steel hose clamps holding the hoses on.  The ends of these s/s clamps are sharp.  Remember, you have to bleed at least once when you are doing this.  And if you are wearing the proscribed rubber gloves (to prevent getting yucky stuff on you) they always manage to get at least one hole torn in them.  

b) disconnect the two electrical wires – one black that goes to the motor and one red that goes to the vacuum switch, and then to the motor.  Note some of these wires have quick release attachments, so don’t get them mixed up when reattaching them. (like I did)

The port side generator is more difficult to remove (due to other diabolical hoses etc that are squeezed into this same space)  and I elected to remove only the pump located on top of the generator rather than the whole generator like the starboard side.  You still must remove the two bolts that you see holding the tank to the support bracket to shift the tank slightly to the side to get to the four bolts holding the pump onto the tank.  The duckbill valves are located on each side of the pump that you now remove to the dock, so you can more easily replace the duck bill valves… four per unit, two each on each side of the pump housing.

You must first remove the hoses (as above described) for the starboard generator to remove the pump housing.

Note:  the input side of the sanitary hose is clamped to an elbow PVC pipe that goes into the vacuum tank, and can be removed with a lot (a lot!!) of twisting and pulling the elbow up — it is pressure fitted into the tank with a rubber gasket.  Just lift and twist it up and out.  It takes a lot of effort especially since you are lying on your side in the crawlspace. It only took me about 2 hours to figure this out!  You should be able to do it in a couple of minutes.

When you remove the output side hoses make sure you have a small bucket and clean up sponges or cloth to catch the two or three cupfuls of yukky stuff that is likely waiting in the hose.  It can be messy so be prepared to clean it up before going on.  Use rubber gloves and quick reflexes.  Or you will be cleaning up a mess – don’t ask me how I know this!!  It will take you longer to clean up the spilled mess than it takes to remove the hoses…  especially when you discover that you are now lying in this mess.  And you may even discover that you now know some new really bad words that should not be said out loud.  So remove any children who may be within hearing distance before starting this part of the job.  And here is where you learn how to remove all your clothes before your wife or significant other allows you to come up from out of that crawl space.  (your clothes get put into a large bag that is deposited into the furthest garbage bag on the dock)

Note:  if you must remove the vacuum switch that is located on the upper part of the tank (the L side of the tank that is sticking up), you slacken off the stainless steel 2 ½ “ clamp and then pull the switch out of the side of the tank.  It should come out easily.  Remember the electrical wires are connected to the “B” side of the switch and NOT the “A” side which are left alone/not connected to anything. We replaced this switch on each tank in March 2012 after finding that the wire connectors on the top of the switches were loose. When reinserting a new switch into the tank be careful of the two rubber gaskets and make sure they are seated correctly and not twisted out of position. I used a little silicone sealant around where the switches attach to the tank to assure there are no air leaks.

Inspect any open hoses and inside the pump housing for calcium buildup that restricts the movement of yukky stuff from the toilet to the holding tank.  I ran an old garden hose through the sanitary pipes to check for blockage. Where I couldn’t get the garden hose through the pipe, I found that replacing the sanitary hose was easier than trying to remove the calcium buildup.  (all hoses replaced with new anti smell hose in March 2012)  When installing NEW hoses, use a heat gun (or hair dryer) on the attachment end of the hose to make it easier attaching the hose.  Remember a heat gun gets things really HOT so be careful not to burn yourself.  Don’t ask me how I know this!

Any PVC Y’s or connectors can be totally cleaned out by putting them into a bath of muriatic acid – be careful and use gloves and eye glasses and DON”T spill it!  The acid eats the calcium and leaves the PVC totally like new.  Wash off the muriatic acid with a lot of water afterwards to remove the acid totally before handling anything.  Muriatic acid is great stuff, but it does burn like crazy!  Trust me when I tell you this!!

After cleaning everything, and installing new hoses as needed, reinstall the vacuum pump and/or the vacuum generator and the electrical wires.  Put it all back in the reverse order you took it out.  You do remember that don’t you?

Only after you have inspected every part of the operation…  from sanitary sewer pipes reconnected – both input and output, and electrical wires reconnected – be sure you get them right, only then do you go up and flip the breaker switches on to see if the units work.   Have someone (I don’t know why my wife refused to do this part, after all I had already done the hard part! – **) down in the crawlspace to check for leaks and run one or two water flushes to make sure everything is back on line.  If you have a small air leak, just switch the breaker switches off after the vacuum pump has cycled to prevent it cycling every so often.  Just remember to switch it back on before flushing the heads/toilets.  

If anyone else wants advice on how to work on their vacuflush head system, you can call me anytime and I will be glad to offer any advice….   like you’d be better off to get an expert to do it, or have your wife read the above and get her to do it, or call your best buddy and tell them they have to experience this wonderful opportunity to do something really different.  But don’t ask me to do it for you.  

** this reminds me of that old saying, “The flogging will continue until moral improves.)

Specific Gravity Test (Flooded batteries only)


1. Do not add water at this time.

2. Fill and drain the hydrometer 2 to 4 times before pulling out a sample.

3. There should be enough sample electrolyte in the hydrometer to completely support the float.

4. Take a reading, record it, and return the electrolyte back to the cell.

5. To check another cell, repeat the 3 steps above.

6. Check all cells in the battery.

7. Replace the vent caps and wipe off any electrolyte that might have been spilled.

8. Correct the readings to 80o F:

  • Add .004 to readings for every 10o above 80o F
  • Subtract .004 for every 10o below 80o F.

9. Compare the readings.

10. Check the state of charge using Table 1.

The readings should be at or above the factory specification of 1.277 ± .007. If any specific gravity readings register low, then follow the steps below.

1. Check and record voltage level(s).

2. Put battery(s) on a complete charge.

3. Take specific gravity readings again.

If any specific gravity readings still register low then follow the steps below.

1. Check voltage level(s).

2. Perform equalization charge. Refer to the Equalizing section for the proper procedure.

3. Take specific gravity readings again.

If any specific gravity reading still registers lower than the factory specification of 1.277 ± .007 then one or more of the following conditions may exist:

1. The battery is old and approaching the end of its life.

2. The battery was left in a state of discharge too long.

3. Electrolyte was lost due to spillage or overflow.

4. A weak or bad cell is developing.

5. Battery was watered excessively previous to testing.

Batteries in conditions 1 – 4 should be taken to a specialist for further evaluation or retired from service.

II. Open-Circuit Voltage Test
For accurate voltage readings, batteries must remain idle (no charging, no discharging) for at least 6 hrs, preferably 24 hrs.

1. Disconnect all loads from the batteries.

2. Measure the voltage using a DC voltmeter.

3. Check the state of charge with Table 1.

4. Charge the battery if it registers 0% to 70% charged.

If battery registers below the Table 1 values, the following conditions may exist:

1. The battery was left in a state of discharge too long.

2. The battery has a bad cell.

Batteries in these conditions should be taken to a specialist for further evaluation or retired from service.

TABLE 1. State of charge as related to specific gravity and
open circuit voltage


Percentage of Charge Specific Gravity Corrected to
80o F
Open-Circuit Voltage
6V 8V 12V 24V 36V 48V
100 1.277 6.37 8.49 12.73 25.46 38.20 50.93
90 1.258 6.31 8.41 12.62 25.24 37.85 50.47
80 1.238 6.25 8.33 12.50 25.00 37.49 49.99
70 1.217 6.19 8.25 12.37 24.74 37.12 49.49
60 1.195 6.12 8.16 12.24 24.48 36.72 48.96
50 1.172 6.05 8.07 12.10 24.20 36.31 48.41
40 1.148 5.98 7.97 11.96 23.92 35.87 47.83
30 1.124 5.91 7.88 11.81 23.63 35.44 47.26
20 1.098 5.83 7.77 11.66 23.32 34.97 46.63
10 1.073 5.75 7.67 11.51 23.02 34.52 46.03