[whagopian]

I ran my 1993 Yamaha 90 today after about 3 months of storage. (Plenty of oil in the engine tank) The boat ran fine at high speed for a few minutes then the engine began to falter and died. My guages are very cloudy and hard to read so I don't know if any of the warning lights are working but I'm pretty sure it is not getting oil. (No Smoke) It will idle ok but after a few moments of mid speed it gets noisy. How can I check the oil flow? Since it still idles fine and runs for a few moments at higher speeds is there a chance I have not yet ruined this engine?

[rodbolt]

hello did you bleed the system after storing it? have you ever cleaned the tank and tank filter? the only way to know is by dissasembly and inspection. overheat will cause the same symptoms. when was the last alarm circuit test done? the oil injection on a yamaha is about as bullet proof as you can make a piece of machinery,however it requires maint like everything else. and maint does not mean just add more oil.

[whagopian]

No I did not bleed the system nor have I ever cleaned the tank. or filter. It's pumping great water preasure and does not feel hot to the touch and the heat alarm works good. Is there a hose that I can pull while at idle to see if oil is moving?

[rodbolt]

hello I suspect rather than a precision blend failure we are dealing with a customer neglect failure. much more common than pump failures.somewhere in your service manual there is an oil consumption test. all the tests require the engine to have a 50-1 premix while running the test. I cannot remember the output specs but you unplug the hose downstream of any inline check valves,if used, and run the engine at the specified RPM for the specified time and collect the oil. the details are in the manual. but remember he pre mix while doing it.

[whagopian]

Running the motor on 50:1 fuel I have removed a few oil lines but NO oil is flowing anywhere. Can someone explain the theory of opperation. What drives the pump?

[bigbrownbuku]

its gear driven from the crankshaft.

[butlp]

Time to purchase a workshop manual! Absolute must if you plan on doing your own maintenance.

[Triton II]

Does the motor run properly on premix? If so it points to the oil pump not working... could be broken or just needs bleeding. After buying the manual as suggested, follow the bleed routine and do the test again. If still no oil flow it could be an airleak in the lines or a broken pump. I'm not an expert but had this problem a few years ago on a Yam 50 and it was because I hadn't bled the oiling system.