Precise Alignment Insures Long Life.

MER Power-Take-Offs
We are known for our clever and durable PTO systems. MER PTO systems reduce maintenance expense because they are built strong and require little ongoing maintenance. Perfect alignment is critical to PTO life and eliminates vibration. Our systems also have the option of polymer drives that absorb the crankshafts acceleration and deceleration as each cylinder fires. This torsional vibration is reduced with our polymer drives.

Many of our PTOs have heavy duty frame members that run forward from the engine block to support the PTO system. These steel rails are one-inch thick by six inches. The pieces are drilled and de-burred so that all members lay flat and square. The fasteners are treated with thread locking compound and then torqued to specifications.  

Most Deere marine engines have standard side-mounted SAE sized PTO locations. Notice that the one shown here to the left has its oil supply line coming in from the engine oil supply system. Return oil flows back to the crankcase after lubricating the PTO bearings. These drive locations can be extended further out from the engine center-line by our PTO accessory drives. 

RH Aux drive

The extender is assembled to the engine by first removing the original SAE drive adapter. Taking the place of the original unit, the extended drive bolts on and has the oil supply re-connected to the new adapter.MER also sells and installs Logan PTO clutches that include front mounted clutches and transmission mounted clutches. These units are engaged by air or hydraulic pressure. The Logan front mounted unit shown here is a very clean system that takes minimal space ahead of the engine. This system works well on either main propulsion engines or generator sets. Logan Front Mount PTO

 Transmission mounted Logan clutches are a convenient way to use that “dead space” most boats have near the marine transmission, rather than taking valuable space in front of the engine. MER provides multiple groove pulleys permit side-mounting of many drive loads such as an extra alternator, washdown pumps, raw water pumps, and belt driven hydraulic pumps. MER custom builds adjustable bracketry for side mounted loads.  

Introduction to Shaft and Engine Alignment
Proper alignment of propeller shafts and engines ensures that the vessel will run smoothly under power, prolongs the life of the equipment, and contributes to the safety of the crew. The shaft and engine work together and both must be in perfect harmony. Engine power is transferred from the rear of the transmission, through the shaft couplings, intermediate shaft, bearings, stuffing box, rear shaft, the stern bearing, and finally the propeller. Note: Not all boats have intermediate and rear shafts; these are more typical of large motor yachts and commercial fishing boats. At times, alignment of the shaft and engine will need adjusting. There is a specific order that must be followed if the job is to be done right, and there are three important factors to consider when the boat is in the water and loaded to normal running weight:

 1. The bores of all shaft bearings and the stuffing box must be concentric and on the low side of the allowed variation of specifications. 

 2. All propeller shafts must be aligned to be concentric with the shaft bearings and the stuffing box.

3. Only after the above two conditions have been met can the engine and transmission assembly be aligned to the shaft.

To summarize, the shaft is first aligned to the boat, and after this work is done, the engine and transmission assembly is aligned to the shaft. Caution: be sure to disable the starter motor before doing any of the work described in this chapter!

Unlike land-based heavy machinery mounted on thick concrete, marine propulsion systems are designed to take considerable twisting and flexing of their platform (the boat) and keep on working. As they are hauled out and blocked for repairs, boats are subject to bending and twisting. In addition, thermal expansion and contraction occur due to temperature changes of the water and air, internal heat sources, and when the sun heats one side of the vessel and the other is in the shade. These fluctuations will change the stresses in the hull and the shafting, and thereby slightly change shaft alignment.

Weather and sea conditions always require the hull and the shafting to bend and flex as the vessel moves through the water. Marine propulsion systems routinely operate in conditions that land-based machinery, such as stationary diesel generators, would only encounter during a severe earthquake.

Sailboat shafts and engine alignment are fairly stable because of the low power ratings at which they operate. High-performance yachts and workboats are designed with fairly light and flexible hull structures, and often the shafts run at high speeds. Fishing boats or freighters differ from other boats because they are heavy on the ends when empty, but, when loaded, they’re heavy in the middle.

When properly designed, built, and maintained, the shafts and the supporting bearings will last and be relatively free of vibration in any application.