ENGINE BED FLATNESS AND CORRECT PROCESS FOR ALIGNMENT

SOME ADVICE ON THE ENGINE BED CONSTRUCTION.

Engine beds are a critical element on for the stability and vibration level of the engine.When determining the engine bed dimensions, full consideration must be given to the stress caused by the propeller’s propulsion and reaction force, the engine’s torque and boat cruising.

It is interesting to have a wide area so we can distribute the engine load. The engine bed must be firmly fixed to the hull. It is interesting to reinforce the front and rear of the bed, and also provide reinforcement every 500 mm (19.69 in.) inbetween.

lt is not advisable to bolt the L-shape angle iron to the engine bed. lf the use of the L-shape angle iron is unavoidable, use it as illustrated and attach it carefully to maximize the horizontal equilibrium of the engine bed.

The engine bed dimensions must include the dimensions of the engine mount. Ensure enough contact area far the engine mount. Far the dimensions of the engine-mount, refer to the engine data for each model.

Below some visual examples of what should be done when the mount can not have a full contact on the engine bed.

NOT RECOMMENDED

RECOMMENDED

The engine bed should leave a 20 mm or larger clearance between the engine bed and the engine body and marine gear. In addition, be sure to leave 20 mm or larger clearance between the hull bottom, and the engine’s oil pan and marine gear. (Measure these values with the height adjusting nuts of the engine’s flexible mount brought down to the lower-most point, where they come into contact with the fixing nut of the stud bolts).

Special attention must be done to the inclination of the brackets in respect to the inclination of the bed.

Difference in the inclination provides an uneven contact as shown on the image below.

Constant lateral stress may cause for stud rupture as shown below.

SOME ADVICE ON THE ALIGNMENT OF THE PROPSHAFT

Before connecting the marine gear drive shaft with the propeller shaft, make sure that the flange surfaces of both parts are parallel to each other, and that their centers are aligned. Then adjust the centering of the engine as follows.

When the propeller shaft is long, place it in the center position by moving it up and down, and then center.

InstaII a clearance gauge on the propeller shaft coupling and measure the circumference against the drive shaft coupling center runout (at four equally spaced points around the circumference).

Then lock the drive shaft, turn the propeller shaft and dial gauge, and measure the outside periphery of the drive shaft and adjust it to the value measured above.

When the values deviate from the above table, make the following adjustment:

(1)          For a deviation of the coupling face, use both adjusting methods in both the vertical and lateral directions.

(2)          Far a centering adjustment in the vertical direction, change the H-dimension by adjust­ing the jack-nut position.

(3)          Far a centering adjustment in the lateral direction, move the long hale side of the enQine mount laterally.

Since rubber mounts stretch with use, raise the jack nut by one turn and install the engine a little bit higher.

(4) After ensuring the allowable dimensions of both A and B, insert the faucet of the propeller shaft coupling about halfway in, and confirm that the clearance between the coupling faces is within 0.2 mm. lf the clearance distance exceeds 0.2 mm, make readjustments.

(5) After finishing centering, tighten the engine mount and the engine tightening bolts.

Tightening torque of flexible mount nuts.

(6)          After tightening the bolts, make sure that the shaft coupling face centering has not slipped. lf slippage is found, readjust.

(7)          Re-check shaft centering after launching when the adhering agent is completely hardened. lf there is any change in the centering, readjust.