BOMBARDIER Johnson 90 Service Manual page 271

POWER TRIM AND TILT- 140
MODES OF OPERATION
Tilt System Pressure Relief
1. lf engine speed exceeds approx. 1500 RPM when operating in shallow water drive mode, oil pres­
sure will increase underneath the tilt pistan. The relief valve
©
(incorporated in the manual ralease
valve ®) will then open.
2. The oil below the tilt pistan will then flow to the reservoir through the relief valve
©.
3. As the power of the engine continuas to exert downward force on the tilt pistan, this will open "Down"
check valve @, thereby allowing oil from the reservoir to flow into the chamber above the tilt pistan.
4. In this way, high interna! pressure is relieved and the engine will slowly tilt downward until it reaches
the highest position in the Trim range.
Thermal Expanslon Relief
1. High ambient temperatura will, through thermal expansion, induce a build-up of oil pressure inside
the PTT unit.
2. Expansion of the oil and the resulting high pressure will open the relief valve
©,
thereby providing
unit protection by directing oil back to the reservoir.
Expanded oíl in the tilt cylinder upper chamber will return to reservoir passing through impact relief
valve CD=>,free pistan check valve Q)=>, thermal relief valve
©
©
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