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Johnson 15 HP - Model No J15RSSM Hard Starting

J

Jackson12

Member
Will welcome any genuine advise, suggestion, recommendation in overcoming this motor from being hard to start after motoring for 30 minutes then standing for a further 15-30 minutes.
 
Hello kimcrwbr1, Sound advise, however what I did not mention that the carb has been kitted with a genuine gasket and seal kit, and rechecked twice to ensure that it is correct to specifications. Also the technical information from an OMC service manual in regards to Synchronisation and Linkage Adjustments has been followed to a tee and everything in this area is "ok". The other matter is the correct adjustment to the idle mixture screw, I find that when on the boat is on the water there is a need to keep on adjusting this mixture setting, at times it appears to be to lean and at other times to rich? When attempting to re-start after standing for approximately 30 minutes the motor gives the impression that there is limited poor engine compression or the motor is fitted with a de-compression devise. However the compression is "ok" when taken either hot or cold!!! Another factor the fuel tank is a plastic non-genuine unit but the fuel line is genuine, the tank does not have an air vent in the actual cap but is relying on the vent in the fuel line. New spark plugs make no difference and when removed show a good burning rate with no excess fuel deposits or are they dry. Fuel is unleaded at 90 octane with no ethanol plus Still Two Stroke oil is also used. Any advise will be most welcome, Cheers jackson12.
 
Good morning, (EST Australia), Although the outboard is some 14 years old the amount of time it has been on the water would be approximately 30 hours. Even for the low running hours the outboard has been well maintained (salt water use). As for the operating temperature it is comfortable, being able to keep your hand on the engine exhaust cover for prolonged periods and there is no signs of paint discolouration on any engine parts. The water circulation tell tail is positive with an excellent flow of water being evident at all RPM'S. Has anybody had any experiences with the top cover (part no 0438061) of the carburettor showing signs of a hair line fracture in the casting? This source of advise was given in a local boating magazine. To confirm your advise with the carburettor air/fuel mixture needle-by screwing the needle inwards will cause a lean mixture (decrease the fuel) and by screwing the needle outwards will cause a rich mixture (increase the fuel)? Regards Jackson12
 
Hello to all helpful members, I have at last found the source of the hard starting and wish to pass some advise. Firstly two compression tests where carried out using the same gauge and when the engine was both cold and hot and the readings indicated to immediate issues, the readings from a third compression test using an alternative gauge illustrated even but slightly lower readings. Running the motor for a full hour on the water with various throttle openings I decided to remove an inspect the two spark plugs, on first observation both plugs looked fine but on close examination a slight water deposit was noticed on the porcelain surrounding the centre electrode - number 1 cylinder. Returning the boat to the garage it was decided to remove the engine cylinder head and on removal it was determined the head gasket had developed a minor defect between the water jacket and the cylinder liner on the top cylinder. Replacement of the head gasket revealed an entirely different engine, easy to start hot or cold and an immense improvement in the engine idle. Lesson learnt is not to rely on a compression test use only as a guide. Cheers Jackson12
 
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