Outboard Motors
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The Markal Thermomelt Stik, a heat sensitive stick similar to a crayon which melts on contact with a surface at a specific temperature, is used to measure power head temperature.
The motor is best checked when operating on a boat. If this is not possible, run the motor in a test tank for at least five minutes, at a maximum speed of 3000 rpm. Mark the surface to be checked with the Stik. The mark will appear dull and chalky. When the surface temperature reaches the temperature rating of the Stik, the mark will melt, becoming liquid and glossy in appearance. On some painted
Figure 5-7. Checking Motor Temperature
surfaces on which the Stik will not leave a mark, it will be necessary to hold the Stik against the surface. See Figure 5-7.
Two Thermomelt Stiks are necessary to check a motor - a 1250 F. Stik and a 1630 F. Stik. With the motor at operating temperature, the 125'” mark should melt and the 1630 mark should not melt.
If the 1250 mark does not melt after a reasonable length of time, the thermostat is stuck open and the motor is running too cold. If the 163° mark also melts, the cooling system is not functioning properly, allowing the motor to overheat. Check for a worn pump assembly, leaky water system, or malfunctioning thermostat.
a. Disconnect throttle linkage at throttle cam and distributor. Remove throttle control shaft with linkage from power head.
Figure 5-5. Removing Heat Switch
b. Disconnect motor cable assembly, by disconnecting leads at ignition coil, safety switch, voltage regulator, shift cable, temperature switch alternator, and choke solenoid.
c. Disconnect starter motor lead. Remove heat sink and diodes, Starter solenoid, voltage regulator, and with motor cable assembly, from power head.
d. Remove carburetor, leaf valve assembly, fuel pump, fuel hoses, and heat exchanger tube as described in Section 3.
e. Remove ignition coil, ring gear cover, and distributor as described in Section 4.
f. Remove rope pulley from flywheel. Using an appropriate flywheel holding fixture, remove flywheel nut. Remove flywheel, using puller (Special T001 #378103). See Figure 5-8.
g. Remove generator stator, and starter motor with Bendix drive, as described in Section 7.
Figure 5-6. Checking Heat Switch
b. Remove hex screws from upper crankcase head.
c. Remove hex screws from lower crankcase head. Remove carbon seal from lower end crankshaft by removing retaining ring. Then remove the other components of seal assembly. Use Truarc No. 4 pliers (Special Tool #307429) to remove retaining ring. See Figure 5-12.
d. Loosen but do not remove entirely the screws holding lower bearing retainer plate to lower crankcase head. Tap crankshaft with rawhide mallet to break seal between crankcase and cylinder, and remove crankcase.
Figure 5-8. Removing Flywheel with Puller h. Disconnect thermostat hoses.
i. Remove rear lower motor cover with exhaust cover, and remove front lower motor cover.
3'. Remove six nuts and six screws attaching power head to lower unit. See Figure 5-9. Lift power head from exhaust housing and place on bench for disassembly. Hoist may be used if available by reattaching flywheel ring gear cover with lifting bail. Power head must be placed on bench so that crankshaft is horizontal and crankcase is facing up. Weight of power head should be supported by the four bosses on the four cylinders. See Figure 5-10.
Figure 5-10. Power Head on Bench for Disassembly
Figure 5-9. Removing Power Head
Figure 5-11. Removing Taper Pins
a. Drive two taper pins out of crankcase and cylinder block assembly. See Figure 5-11. Remove six large and eight small screws attaching crankcase to cylinder block.
Pistons, connecting rods, rod bearings, etc. are wearing parts and seat with the operation of the motor. Because of this, it is essential to maintain their original positions at reassembly. Mark each
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