Boats with engine room space restrictions.

Maximum Bore: 45mm, 1.77"

This a standard stocked unit. About half the size of the Mod II Easy Lok Unit.

It is the smallest physical size but can handle yachts with a maximum propeller shaft diameter of (45mm) 1.771 inches. One of the most popular propeller sizes is 1 ¾” so our new Mod I can handle it.

This was the first unit to hit the market in 1979.

In late 2023 Shaft Lok Inc. upgraded the Mod I with a larger deep-groove ball bearing 6911ZZ by Nachi to include maintenance free double bearing shields. The Basic Dynamic Load Rating is 3,600 Pounds.

The Mod I Housing, is made of hard marine urethane which is imperious to salt air. The unit’s housing will last decades.

The Mod I Easy Lok unit has a 316 Stainless Steel rotating 4.08” (103.6mm) diameter disc with a 45 degree locking ramp. The hub of the unit, in which the propeller shaft is contained is also made of the best material to fight salt air 316 Stainless Steel.

The length of the unit is 7.08” (180mm). The width at the Spring Adjustment Screw is 3.346” (85mm). The required propeller shaft space is equal to length through the bore 1.57” (40.0mm).

Boats with some engine room space restrictions.

The maximum Mod II Easy Lok bore size is 2.25” or 57.15mm.

The width of the unit is 2.00” or 50.8mm.

The Mod II Easy Lok unit is Shaft Lok’s most popular unit. Out of approximately 1400 units shipped since 1979 about 70% are Mod II units. This means the components are usually in stock.

A question frequently asked: “How is the unit secured to the propeller shaft?” There are four 3/8” 9.525mm diameter x 24 thread stainless steel cup pointed set screws in the stainless steel hub that are fastened to the shaft. The shaft needs to be dimpled for which a drill bit is provided. This Mod II unit is about twice the size of the Mod I Easy Lok unit and about half the size of the Mod III Easy Lok unit. Feathering propellers produce more speed when sailing and result in more drive train life.

Boats with fewer engine room space restrictions.

Max Bore of 2.25" or greater

This is the largest standard unit that is stocked as finished housings and rotating disc assemblies which can be assembled, tested and shipped in less than a day. This standard unit has the second highest maximum torque (for the highest torque see Card # 5) of all our stocked units which is important if you have a fixed bladed propeller(s).

If your boat has one or two FEATHERING OR FOLDING PROPELLERS with a propeller shaft diameter smaller than 80mm (3.149”) see the Mod II Easy Lok units in Cards # 2 & # 3.

1. The Maximum Propeller Shaft Diameter is 80mm (3.149”).

2. The easiest way to determine if this unit will fit in your boat is to make a cardboard rotor template. The rotor template should be at least 11.75 inches (299mm) diameter with a centered hole equal to the actual propeller shaft diameter. Cut the template into two equal parts and slide one part along the shaft in the area where the Shaft Lok unit is to be mounted. As you can see on the drawing the length through the bore of the unit is 2.690” 68.33mm.

3. The “Easy Lok” means that the rotating disc has a 45 degree ramp instead of a two “Vee” design. This feature makes the unit EASY TO LOCK.

4. This Mod III unit can be locked with a Marine Cable or a Simple Spring Locking System like the other standard units.

Boats with no engine room space restrictions.

Bore 64mm and smaller

This is the largest standard unit that is stocked as finished housings and rotating disc assemblies which can be assembled and tested in less than a day. This standard unit has the second highest maximum torque (for the highest torque see Card #7) of all our stocked units which is important if you have a fixed 3 to 5 blade propeller.

If your boat has one or two FEATHERING OR FOLDING PROPELLERS with a propeller diameter smaller than 80mm (3.149”) see the Mod II Easy Lok units in Cards # 4 & # 5.

1. The Maximum Propeller Shaft Diameter is 80mm (3.149”). Will the Mod III FIT ? The propeller shaft is installed into the rotating disc assembly that is 11.484” diameter (291.7mm). The radius is 5.742” radius (145.9mm). The rotor template should be at least 11.75 inches (299mm) diameter with a centered hole equal to the actual propeller shaft diameter. Cut the template into two equal parts and slide one part along the shaft in the area where the Shaft Lok unit is to be mounted.

2. The “Easy Lok” means that the rotating disc has a 45 degree ramp instead of a two “Vee” design. This feature makes the unit EASY TO LOCK. See Card # 8.

3. This Mod III unit can be locked with a Marine Cable or a Simple Spring Locking System like the other standard units.

Boats with no engine room space restrictions.

Max Bore of 80mm

The Maximum Propeller Shaft Diameter is 4.330” (110mm).

The Shaft Lok Inc. Mod IV, V, and VI units are designed for these yachts.

These huge yachts are mostly motor vessels but there are a few sail boats like the beautifully restored schooner S/Y ERNESTINA that returned to New Bedford, MA recently. M/Y Rocket One is a million dollar motor yacht, both of these boats are online. The captains and owners of these vessels like to use one engine when:

A. To dramatically increase the miles per gallon of the expensive diesel… which increases the yacht’s range.

B. Increasing the efficiency of the vessel also reduces the operation monthly hours on the motors stabilizing the yacht’s relative value.

C. Also, it allows the vessel to keep powering while the other drive train system is being maintained. However, the drive train that is shut down needs it’s propeller locked as the vessel is powering on the other motor. Allowing the propeller to freewheel could cause significant transmission damage because the transmission gets it’s lubrication from the engine.

The Shaft Lok unit(s) must be designed to handle massive amounts of torque generated by the yacht speed and propeller size.

This enormous static torque can be achieved by building a strong single unit using multiple standard short pins, the locking pin and spring systems in the housing to hold the large locking pin stationary.

This design of the Mod IV, V and VI is just a simple upgrade from the 1979 patented arrangement. The components are designed to handle the loads involved

Please submit your yacht details including the yacht’s name and contact information for price and delivery details.

The Maximum Propeller Shaft Diameter is to be determined by the application.

The Shaft Lok Inc. Mod IV, V, and VI units are designed for these yachts.

These huge yachts are mostly motor vessels but there are a few sailboats like the beautiful restored schooner S/Y ERNESTINA that returned to New Bedford, MA recently. M/Y Rocket One is a million dollar motor yacht, both of these boats are online.

The captains and owners of these vessels like to just use one engine at times:

A. To dramatically increase the miles per gallon of the expensive diesel… which increases the yacht’s range.

B. Increasing the efficiency of the vessel also reduces the operation monthly hours on the motors stabilizing the yacht’s relative value.

C. Also, it allows the vessel to keep powering while the other drive train system is being maintained. However, the drive train that is shut down needs it’s propeller locked as the vessel is powering on the other motor. Allowing the propeller to freewheel could cause significant transmission damage because the transmission gets it’s lubrication from the engine.

The Shaft Lok unit(s) must be designed to handle massive amounts of torque generated by the yacht speed and propeller size.

This enormous static torque can be achieved by building a strong single unit using multiple standard short pins, the locking pin and spring systems in the housing to hold the large locking pin stationary.

This design of the Mod IV, V and VI is just a simple upgrade from the 1979 patented arrangement. The components are designed to handle the loads involved.

Please submit your yacht details including the yacht’s name and contact information for price and delivery details.

The Maximum Propeller Shaft Diameter is 6.5” (165.1mm).

The Shaft Lok Inc. Mod IV, V and VI units are designed for these yachts.

These huge yachts are mostly motor vessels but there are a few sailboats like the beautiful restored schooner S/Y ERNESTINA that returned to New Bedford, MA recently. M/Y Rocket One is a million dollar motor yacht, both of these boats are online.

The captains and owners of these vessels like to just use one engine at times:

A. To dramatically increase the miles per gallon of the expensive diesel. This will increase the yacht’s range.

B. Increasing the efficiency of the vessel also reduces the operation monthly hours on the motors stabilizing the yacht’s relative value.

C. Also, it allows the vessel to keep powering while the other drive train system is being maintained.

However, the drive train that is shut down needs it’s propeller locked as the vessel is powering on the other motor. Allowing the propeller to freewheel could cause significant transmission damage because the transmission gets it’s lubrication from the engine.

The Shaft Lok unit(s) must be designed to handle massive amounts of torque generated by the yacht speed and propeller size.

This enormous static torque can be achieved by building a strong single unit using multiple standard short pins, the locking pin and spring systems in the housing to hold the large locking pin stationary.

This design of the Mod IV, V and VI is just a simple upgrade from the 1979 patented arrangement. The components are designed to handle the loads involved.

Please submit your yacht details including the yacht’s name and contact information for price and delivery details.

This is the second option, besides the Simple Spring Locking System, to lock the Shaft Lok unit.

These cables are all made to order and are available in any length.

The cable prices are included in our formal quotation. The cable is attached to the cap plate on top of the unit. The cap plate is bolted to the unit. The cable can be routed to the helm station. Most live onboard sailors position the cable below deck to protect it from inadvertent use. Pushing on the black knob on the cable will move the locking pin down to contact the rotating disc. If the vessel is powering and the black knob is pushed in the long locking pin working end would be damaged.

Yes, the locking pin can be replaced but it is expensive.

These cables have stainless steel terminals. The low friction liner inside the protective casing provides easy movement of the 0.075” diameter stainless wire which is connected to the black knob. The 0.075” SS wire is also contained in the long locking pin with four set screws. This pin physically contacts the rotating disc through which the propeller shaft passes.

When installing the Marine Control Cable try to keep the number of “bends” and “turns” to a minimum which will keep the force necessary to lock the unit at a minimum.

See the attached Patent Drawing.

Please specify length during order.

This S.S.L.S is one of the two devices that lock all the Mod I thru Mod III Shaft Lok Units. It is mounted on top of the Shaft Lok Unit. Just push down on the black knob to lock.

SSLS is inexpensive, easy to install and compact.

To operate the SSLS one must enter the engine room, which may be difficult on some yachts. However, to LOCK the Shaft Lok unit, the propeller must be rotating slowly.

Shaft Lok is an excellent LOCK but as a brake “not so much”.

The SSLS operator should be able to see the propeller shaft easily. Over time the operator will become aware of what shaft rotation speed is required to lock the unit. The sailor can inform the captain if more or less speed is necessary. The Shaft Lok unit automatically unlocks when the engine is started and put into gear. The locking pin, that holds the rotating disc, travels up into the housing allowing the disc to rotate should the captain want to use the motor to move the vessel. The short pin in the housing holds the locking pin in the unlocked position. When the unit is locked the short pin also holds in the locked position. See the Patent Drawing attached: 2 pages down.