Yamaha 50 1985 2-stroke cooling problem

[Mikko]

Mystery tell-tale "pee" problem happens randomly after driving short or longer time when pee is totally cut and engine overheats. Then after cooling a bit, everything is ok again. Impeller change did not change the situation at all. Most of the time "pee" is very strong,, but this mystery water cut happens almost every trial and may disappear for long time. Has anybody got same experience? I pressed air through the copper tube from water pump and it came out from tell-tale,. I do not know the passage after the tube when it comes to the bottom of water cover and then to tell-tale. It seems that the problem should be somewhere there.

 

[99yam40]

maybe using some Ridlyme marine descaler will help before trying to tear the motor apart.

 

[Mikko]

Water cut off happens suddenly on-off way, so it sounds like some loose piece of something is closing the water passage? I don't know how the flushing should be done with this Rydlyme.

 

[99yam40]

you can look on line on how to do it, but if it is a piece of rubber water pump impellor floating around in there ,descaler will not dissolve that

Before you do anything else,
drop the lower unit,
hook up a water hose to the pipe heading up to the power head,
remove the thermostat
turn on the water to the hose and let that run for awhile
try to catch the water in a clean bucket to see if anything comes out
good luck

 

[Mikko]

When does water enter the tell-tale? Immediately after passing the pipe and lower part of the power head? This is how it goes in many outboards, just to indicate that pump is working, nothing else. If it goes through the water jacket up to thermostat and then back to tell-tale, there are many more possibilities for the problem.