Yanmar Pleasure Boat Marine Engine Help

Overview - Front Power Takeoff

A front power takeoff is often used to drive a refrigeration compressor, water-maker compressor, additional alternators, a hydraulic winch pump, etc. As excessive side loads may break the crankshaft, the Yanmar recommended MAXIMUM FRONT PTO at various rpm for individual engine models can be calculated HERE.
The way the accessory is mounted is critical. The two mounting systems dealt with here are referred to as 'A' type and 'D' type drives.
The 'A' type is side loaded with no support for the crankshaft.
Excessive load or excessive belt tightening can break the crankshaft, I've seen it happen where the 'fridgie' used a bar to tighten his ' V ' belts.

The 'D' type is supported by the machinery or a pillar block bearing between the crankshaft and the driven load and can therefore handle a lot more horsepower than an 'A' type drive. If you have a look at the 6CX-ETE front PTO graph you will see a considerable difference between the two drive types.

The left hand 'A' type drive drawn below shows a support frame mounted integrally with the engine, this is OK.
The right hand 'A' type drive shows an accessory mounted on the engine bed. This type of installation will cause unpleasant vibration, break the crankshaft or mounting / adjustment assembly or at the very least require excessive maintenance.)

Keep the angle within 30deg of the horizontal.

'A' type, side view showing the dimension, 'Overhang (L)' required to calculate the allowable load.

'A' type, top view

This 'A' type pto below should have had the excess pulleys machined off. The additional weight of the alternator on this larger engine (6CX-ETE) is insignificant and does not affect the mount.

'D' type couple can handle more horsepower as the crankshaft is supported.

Installation Tips - Front Power Takeoff

• The flexible engine mount under the accessory should be changed on GM and JH series engines. The flexible mount can be replaced with a stiffer one. e.g. a mount with 75 written on the rubber part should be replaced with a mount with 100 written on it, check with your dealer. If they're any good they'll just swap it fo the stiffer one. The higher the number the stiffer the mount, the more weight it is designed to support.
• If you make a complete new mounting bracket assembly as part of the support frame, do not move the engine mount position, the resulting vibration annoys the owner and breaks things on the engine.

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