Expert: Jeff Grigg - 1/18/2008

Question
QUESTION: I own a 1984 9.9hp Yamaha outboard for my 1984 Hunter 25.5 sailboat. Often the telltale stream of water is but a trickle, sometimes nothing, and sometimes a strong stream. When it trickles or is non-existent I worry. Had the impeller replace about 6 months ago. Cleared all the water lines, took them off this past Sunday and ran the engine for a few minutes with but a few drops of water coming out of the engine. Can there be a blockage between the engine and the intake/outflow opening on the foot of the engine? What can I do to feel comfortable and have the flow coming out nice and strong at all times? Where can I get a drawing showing how the cooling system works?

ANSWER: Most service manuals have the information you need about  the cooling system.
The slightest piece of debris can clog the tell-tale on an outboard. you can either blow back through the outlet with compressed air or a small wire, like fishing leader wire will work also. It is a very common problem.
Jeff

---------- FOLLOW-UP ----------

QUESTION: As I pointed out in my original question, I had removed all the tell tale hoses and cleared them. Therefore the small wire had already been used. With the lines removed, there was still only a trickle of water coming out the engine. Hence my question, could the blockage be between that point and the intake point at the foot of the motor, near the propeller? Or could the problem be in the thermostat that had not opened completely?

Answer
The problem probably isn't in the water pump or the main water tube as they are quite large. More than likely the problem is in the exhaust cover where the nipple for the tell-tale is. You could have a build up of corrosion or some debris like some large grains of sand or shell. The tell-tale should operate whether or not the thermostat is opening.
Jeff