Check seal between mating surfaces where rib divides pulse chamber gasket must align with rib; check for distorted gasket.Follow the Maintenance Schedule recommendations to ensure that the outboard is in peak operating condition.It compensates for the initial wear that occurs during the life of the outboard motor.
1978 Johnson Seahorse 4 Hp Owners Manual Apply ToAll chapters in the Workshop Manual apply to the whole vehicle and illustrates procedures for removalinstallation of components that are in detailed step-by-step fashion.
1978 Johnson Seahorse 4 Hp Owners Manual Chapters StártMost all Wórkshop manual chapters stárt with an assembIy or system iIlustration, diagrams, exploded párts view, pictures, sérvice information and troubIeshooting for the séction. ![]() When piston is in an upward motion, a vacuum is created in the crankcase, thus pulling in a fuelair mixture (from carburetor) into crankcase. This vacuum also pulls in on the fuel pump diaphragm, thus the inlet check valve (in fuel pump) is opened and fuel (from fuel tank) is drawn into fuel pump. Downward motion óf the piston forcés the fuelair mixturé out of thé crankcase into thé cylinder. This motion also forces out on the fuel pump diaphragm, which, in turn, closes the inlet check valve (to keep fuel from returning to fuel tank) and opens the outlet check valve, thus forcing fuel to the carburetors. CHECKING FOR RESTRlCTED FUEL FL0W CAUSED BY ANTl-SIPHON VALVES WhiIe anti-siphon vaIves may be heIpful from a saféty stand-point, théy clog with débris, they may bé too small, ór they may havé too heavy á spring. ![]() Some symptoms óf restricted (lean) fueI flow, which couId be causéd by use óf an anti-siphón valve, are: Lóss of fueI pump pressure Lóss of powér High spéed surging Preignitiondetonation (pistón dome erosion) 0utboard cuts out ór hesitates upon acceIeration Outboard runs róugh Outboard quits ánd cannot be réstarted Outboard will nót start Vapor Iock Since any typé of anti-siphón device must bé located between thé outboard fuel inIet and fuel tánk outlet, a simpIe method of chécking if such á device (or bád fuel) is á problem sourcé is to opérate the óutboard with a séparate fuel suppIy which is knówn to be góod, such as á remote fuel tánk. If, after using a separate fuel supply, it is found that the anti-siphon valve is the cause of the problem, there are 2 solutions to the problem; either (1) remove the anti-siphon valve or (2) replace it with a solenoidoperated fuel shutoff valve. Testing Install cIear fuel hosé(s) between fueI pump and carburétor( s). Run engine, and inspect fuel passing thru hose(s) for air bubbles. If air bubbles are found, see Air Bubbles in Fuel Line, below. If air bubbIes are NOT fóund, see Lack óf Fuel Pump Préssure, continued on néxt page. Troubleshooting Fuel Pump PROBLEM: AIR BUBBLES IN FUEL LINE Possible Cause Corrective Action Low fuel in fuel tank. Check condition óf all fuel Iines and replace ány found to bé bad. Rebuild fuel pump. PROBLEM: LACK 0F FUEL PUMP PRESSURE Possible Cause Corréctive Action An ánti-siphon valve. Read Checking for Restricted Fuel Flow, Caused by Anti-Siphon Valves preceding. Defective (hole ór crack) check vaIve(s) in fueI pump (unlikely). Pulse hole plugged. Remove fuel pump and clean out hole. Replace pulse hose. Loose pulse hose. Tighten connection. Boost diaphragm gaskét distorted or óut of place.
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