1986 Yamaha 90 ETLK cooling flow problem

[guerryb@hotmail.com]

I recently picked up a 1987 Yamaha 90 ETLK. When testing on the trailer, and on ear muffs, I don't get water from the tell tale and the engine quickly gets hot. Apparently the previous owner was neglectful with proper flushing.

The engine has a brand new head with poppet, thermostat, and water pump. Before cranking the engine for the first time, I inspected it thoroughly and performed a compression check revealing 125-PSI on all three [cylinders] when the engine is stone cold. All looks good, it starts easily and runs smoothly.

I noticed no water out from the tell tale and started investigating. With ear muffs, it never pushed water up and out of the tell tale. I pulled the thermo cover and found a small amount of salt crustiness. I cleaned that out and reinstalled them but no water ever came from the tell tale when running at any RPM.

I removed the thermostat cover again and ran the engine with it off. Water pushed out the top with the foot in a barrel of water and no water hose pressure. Assuming I did not get the pump primed at first, I reassembled the thermostat section and cranked it again. No water.

Assuming there were blockages in other areas, I did the salt-away process by pouring it thru the thermostat hole, letting it soak for 20 mins and then running the engine briefly to push any debris out the top. The cleaning solution flowed out through the foot and did not seem to find any restrictions. While apart, I tested the thermostat in a pot on the stove. It started opening at approximately 160-degrees. The thermostat is shiny brass and appears to be new. The poppet valve and O-ring appear new too.

I reassembled again and no luck. With the thermostat installed I get no flow out the tell tale and the engine quickly gets hot. I don't let [the engine heat rise to the level that would sound an] alarm. I just use a laser thermometer and read the heads near the plugs, and I shut off the engine if the readings on the thermometer approached 180-degrees externally. With the thermostat OUT, the temperatures all over the head and exhaust plate on the side are very cool, never reaching 100-degrees. I assume inside temperatures are getting hot, but not reaching dangerous levels. Also, water ALWAYS flows out the front water return hole on the foot regardless of whether thermostat is in in or out.

Any ideas why I see no tell tale water and it gets hot quickly? Why no flow with the thermostat installed and plenty of flow with it removed but the cover is installed? If the thermostat is normally closed, I should still have tell tale water flowing, right? Any help will be most appreciated!

[chummy70]

You check water pump? Impeller?

[99yam40]

did you run a weed wacker line or heavy mono up the TT while running or blow some compressed air up the TT while running to see if that moved things around to get a flow out of the TT?

I know that will not solve an over heat, but need to make sure TT is clear of obstructions

[guerryb@hotmail.com]

Many thanks for all the advice. As of today it seems to be working properly.

Still, I am scratching my head because none of this makes sense. It is most likely that I was mistaken in my recollection of what was going on. I now know there were times that I had the muffs on and the water hose off when I ran it in the barrel of water. Ultimately, scaling is/was the problem and i will work it from that determination.

To reiterate, the motor has a brand new pump assembly and head including thermostat, poppet and cover. Also, water always flowed out the Tell Tale if the thermostat was removed, thus the tube and nozzle were never clogged.

Currently I think the problem was caused by an excessive amount of scale build up in the exhaust baffle section. A new head assembly and water pump were just installed, but the exhaust baffle did not appear to have been removed for service. After reading in many other threads, I too chose to not attempt the baffle removal since it seems everyone else had catastrophic numbers of bolts ring off.

I flushed the upper cooling channels several more times. I alternated between distilled cleaning vinegar and "Dollar tree" Awesome CLR cleaner. Each time I added cleaner to the system, I would have the motor tilted all the way up so the fluid would stay up in the motor section and not run back out the foot.

After allowing the cleaner to sit for about 30 mins, I dropped the motor back down into the water barrel and ran the motor for about 3-5 mins with the thermostat cover off. With the cover off, the foot in a water barrel, and ear muffs on with full water hose pressure, a full and fast flow of water pushed out of the thermostat and poppet holes. Any lose scaling was pushed out the top. Any dissolved salt or scaling would also flow out of the motor this way, and not go into the other coolant water passages in the head and baffle.

I've cranked the motor (cold) a half dozen times or more since it started working again. Every time it starts and quickly delivers a strong stream from the Tell Tale. next step is an all telling sea trial!

In the future, I'll do a vinegar / CLR flush periodically to make sure the flow paths are not hindered. I plan on stocking up on $1 a gallon "distilled cleaning vinegar" to clean the cooling passages as I flush from a barrel. Hopefully this one has many more years to give.