As of January 2011, IsoFlex Technologies manufactures eleven (11) different 4-bolt couplings designed to work with a broad range of gearbox flanges and propeller shaft flanges. Development of new coupling shapes and sizes is an ongoing effort at IsoFlex. If you do not see the coupling shape/size that meets your needs, just call IsoFlex or Tides Marine for additional help.
Pictured below are photos of the IC-4500-95 with a “male” index ring designed to fit within a female index ring on the gearbox flange. This is for demonstration purposes only. In the field, some gearbox flanges have female index rings. IsoFlex makes couplings for this configuration as well.
Each GEARguard coupling order contains the coupling and the hardware (bolt set) necessary for your installation.
2
Side A (with its male index ring) is positioned against the gearbox flange (which, in this example, has a female index ring).
Side B (with its female index ring) is installed against the prop shaft flange (which, in this example, has a male index ring).

A bolt set is used to connect the IsoFlex coupling between the gearbox flange and the propeller shaft flange. There are four unique bolt sets which fit one or more of the 8 unique bolt patterns found in the 4-bolt coupling product line.
Please contact Tides Marine if you have any questions.
This is Bolt Set IC 4200/4400/4600, which contains the following:
Four (4) hex head M10 bolts 40mm in length - the “long” bolts.
Four (4) hex head M10 bolts 30mm in length - the “short” bolts.
Four (4) M10 hex nuts used with the long bolts.
Eight (8) M10 lock washers - use one with each bolt.
If your gear box flange is thicker than .500”, the long bolts in this set are too short.
If your propeller shaft flange is thicker than .750”, the short bolts in this set are too short.
Please contact Tides Marine for a new bolt set to complete your installation.
This bolt set is supplied with the following IsoFlex couplings:
IC 4200
IC 4400
IC 4600
This is bolt set IC 4300/4800, which contains the following:
Four (4) hex head 3/8” x 1 1/2” bolts - the “long” bolts.
Four (4) hex head 3/8” x 1 1/4” bolts - the “short” bolts.
Four (4) 3/8” hex nuts used with the long bolts.
Eight (8) 3/8” lock washers - use one with each bolt.
If your gear box flange is thicker than .375”, the long bolts in this set are too short.
If your propeller shaft flange is thicker than .750”, the short bolts in this set are too short.
Please contact Tides Marine for a new bolt set to complete your installation.
This bolt set is supplied with the following IsoFlex couplings:
IC 4300
IC 4800
3

4
This is Bolt Set IC 4500/4550/4700, which contains the following:
Four (4) hex head 7/16” bolts 1 3/4” in length - the “long” bolts.
Four (4) hex head 7/16” bolts 1 1/2” in length - the “short” bolts.
Four (4) 7/16” hex nuts used with the long bolts.
Eight (8) 7/16” lock washers - use one with each bolt.
If your gear box flange is thicker than .500”, the long bolts in this set are too short.
If your propeller shaft flange is thicker than 1.00”, the short bolts in this set are too short.
Please contact Tides Marine for a new bolt set to complete your installation.
This bolt set is supplied with the following IsoFlex couplings:
IC 4500
IC 4550
IC 4700
This is Bolt Set IC 4900, which contains the following:
Four (4) SHCS* 1/2” x 2 1/2” UNC bolts - the “long” bolts.
Four (4) SHCS* 1/2” x 1 3/4” UNC bolts - the “short” bolts.
Four (4) 1/2” hex nuts used with the long bolts.
Eight (8) 1/2” lock washers - use one with each bolt.
*SHCS - Socket Head Cap Screw
If your gear box flange is thicker than 1.00”, the long bolts in this set are too short.
If your propeller shaft flange is thicker than 1.00”, the short bolts in this set are too short.
Please contact Tides Marine for a new bolt set to complete your installation.
This bolt set is supplied with the following IsoFlex couplings:
IC 4900

A) Loosen the gearbox and propeller shaft flange bolts just enough to insert a feeler gauge between the flanges around the entire circumference of the parts.
5

B) Align the flanges (using the adjusting nuts on the engine mounts) to within .003” (.07mm) around the circumference of the flanges.
A) Remove the flange bolts and separate the gearbox flange from the propeller flange (the flanges).
The male index ring on the IsoFlex coupling is 4mm (.15”) tall. This index ring must fit into the female index ring on the gearbox coupling without “bottoming out”.
To ensure a proper fit, measure the height of the metal index ring on the propeller shaft flange. If this dimension is less than 4mm (.15”), the male index ring on the IsoFlex coupling may be too long to fit correctly within the gearbox flange.
Tides Marine has measurement disks available for your use in this step. Contact Tides Marine at 800-429-0949 for more information. There should be no space between the coupling and flange surfaces .
Coupling sits flat against gearbox flange.
There should be no space between coupling and flange.
6
Properly installed, the coupling sits flat and tight against the gearbox flange.
If the male index ring on the IsoFlex coupling is longer than the female index ring on the gearbox flange is deep, the coupling will not sit flat and tight against the gearbox flange.

Next, in this example, you want to make certain the female index ring on the coupling fits correctly against the male index ring on the propeller shaft flange.
Again, once in place, the surface of the coupling should sit flat and tight against the propeller shaft flange.
Coupling sits flat against propeller shaft flange.
There should be no space between coupling and flange.
Properly installed, the coupling sits flat and tight against the propeller shaft flange.
If the make index ring on the propeller shaft flange is longer than the female index ring on the IsoFlex coupling, the coupling will not fit in this assembly.
If an incorrect fit is found, please stop work and contact Tides Marine to discuss your options.
7

8
The IsoFlex couplings electrically isolate the propeller shaft from the engine and gearbox.
To restore this connection, an internal coil spring (option available through IsoFlex) may be fitted as shown here.
All four-bolt IsoFlex couplings will use the small coil spring.
Small coil spring Medium coil spring Large coil spring
Insert an internal coil spring into the female index ring of the
IsoFlex coupling, as shown.

A) Hold the IsoFlex coupling against the gearbox flange, mating the index features of both parts.
Male index ring on the IsoFlex coupling faces the female index ring on the gearbox flange.
Female index ring on the IsoFlex coupling faces the female index ring on the gearbox flange.
B) Rotate the IsoFlex coupling to align the countersunk T-bushings
(referred to as the gearbox bushings) in the coupling with the holes in the gearbox flange.
Holes are lined up
C) Insert the “longer” bolts into the countersunk T-bushings and through the gearbox coupling.
9

10
D) Place the lock washers over the bolts and affix the nuts. Apply some sort of thread lock liquid/paste (LOCTITE) to the threads before securing the nuts.
E) Tighten these bolts to the required torque in two steps.
First, tighten (in the sequence shown in the drawing below) to half of the total recommended torque rating for the bolts in your coupling. Then tighten (using this same sequence) to the final recommended torque rating as listed in the charts below. Lock washers should be fully compressed.
NOTE:
Over-tensioning ANY of the bolts during assembly may cause internal damage to the IsoFlex coupling. In extreme cases, the steel inserts may become distorted or spin within the coupling. The result is a coupling that will not function properly.
These charts indicate the recommended assembly torque to correspond with your IsoFlex coupling bolt size.

Lock washers fully compressed.
A) Fit the propeller shaft flange to the IsoFlex coupling, rotating the propeller flange to align the remaining threaded inserts with the holes in the propeller shaft flange.
11

B) Place a lock washer under the bolt head.
To make it easier to remove the propeller shaft coupling in the future, apply a thin layer of waterproof grease to the threads of the “short” bolts before securing the bolts into the coupling.
Do not use thread locking compound (Loctite) on these internal bolts as damage may occur when upon coupling removal.
12
C) Insert the bolts (with lock washers) through the propeller shaft coupling and turn into the threaded inserts in the IsoFlex coupling.
D) Tighten these bolts to the required torque in two steps.
First, tighten (in the sequence shown in the drawing at left) to half of the total recommended torque rating for the bolts in your coupling. Then tighten (using this same sequence) to the final recommended torque rating. Lock washers should be fully compressed.
See torque charts on page 10.
NOTE:
Over-tensioning ANY of the bolts during assembly may cause internal damage to the IsoFlex coupling. In extreme cases, the steel inserts may become distorted or spin within the coupling. The result is a coupling that will not function properly.

A) Slowly rotate the shaft by hand with a dial indicator on the gearbox output flange - then the propeller flange. Run-out of approximately .004” (.01mm) is acceptable for most power transmission applications.
Check the GEARguard coupling for heat build-up after 2 hours of sea trials. If the coupling is noticeably hotter than the gearbox flange (or if bolts have become loose), this is an indication that the flanges are misaligned. This needs to be corrected to avoid any damage to the coupling or other drive line components.
After approximately 15 hours of operation, re-check the bolts in the propeller shaft flange for torque accuracy.
Please note the diagrams in this section which describe a “Male” index ring and “Female” index cavity. These are sometimes referred to as pilots. They maintain the concentricity of the power transmission shafts.
13

It is very important to check for misalignment of the gearbox and propeller shaft flanges. Both “displaced” and “angular” misalignment can be present in your installation. Please see diagrams above.
These types of misalignment should be minimized (maximum allowable between flanges being .005” or .125mm). Otherwise, service life of the IsoFlex GEARguard coupling will be noticeably reduced.
Certain applications require an adaptor (sometimes referred to as a cotton reel or spool) to be fitted to the output flange of the gearbox. This adaptor will 1) move the GEARguard coupling far enough aft to clear any obstructions near the back of the engine
(oil pumps, etc.) and 2) permit a different bolt pattern between the output flange and the required coupling.
Please note the diagram above.
If your installation requires an adaptor, IsoFlex recommends that it be manufactured by a marine engineering company from
1040 grade steel or equivalent and machined to industry tolerances. Please check carefully for fit and run-out once installed.
14
As gearbox manufacturers’ dimensions and specifications are subject to change, it is necessary to check all dimensions to ensure the GEARguard coupling fits and works correctly.
All IsoFlex couplings are manufactured from engineering-grade polymers (thermoplastics). As a result, dimensional changes may occur depending upon ambient operating conditions.
Tolerances on all machined index rings: +/- .002” (+/- .05mm) @ 25° C.
All other dimensions: +/- .020” (+/- .5mm) @ 25°C.

_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
_______________________________________________________________________________________________________
If you have any questions about installing your IsoFlex coupling, please contact us at:
Tides Marine, Inc.
Phone: (954) 420-0949
Toll Free: (800) 420-0949 www.tidesmarine.com
15

IsoFlex:
IsoFlex Technologies Pty Ltd.
Unit 33, 75 Waterway Drive
Gold Coaast Marine Precinct
Coomera, Queensland
Australia 4209
Phone: 011 61 7 5556 0924
Fax: 011 61 7 5556 0984 info@IsoFlex.com.au www.IsoFlex.com.au www.IsoFlextech.com
U.S. Agent:
TIDES MARINE
3251A S.W. 13th Drive Deerfield Beach, FL 33442
Toll Free Phone: (800) 420-0949
General Phone: (954) 420-0949
General Fax: (954) 420-0945
Order Fax: (954) 420-5234
Email: customerservice@tidesmarine.com www.tidesmarine.com
IsoFlex Coupling INSTR (Rev. 01/24/11)