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3 cyl high speed overheat

S

scott_s

Advanced Contributor
"C80TLRV ('97) wat

"C80TLRV ('97) water pump, thermo, poppit valve good. good flow, and pressure. head cover has been removed and was clean. temp switch is new. plugs look good, no sign of detonation. runs good. last test, 4600 RPM. no problems. 4900 RPM. overheat alarm, and RPM reduction. shut down immediatly, and checked temp. (laser thermo.) head(from side)168f. cover 150f. crank. @ flywheel 170f. what am I overlooking??"
 
"Scott,

I'm not sure if

"Scott,

I'm not sure if you removed the cylinder head or not; if you did not, you probably should. These engines usually have anodes in the water jackets under the head, and they need to be checked regularly.

Other possibilities are a partially blocked water tube or water jacket, loss of pressure through a gasket or worn casting, water pump housing not sealing properly.

Tony"
 
"to be honest, I did not remov

"to be honest, I did not remove the head. originally suspected a stuck poppit valve.( it was) repaired it and no change. replaced water pump, although it looked ok. tell tale very strong. may have picked up 400 rpm with all this, but still alarm. took off thermo housing and ran on flusher. plenty of flow at thermo/poppit. figured any restiction had to be on the way out. removed cyl. cover. all clean. replaced switch just in case it was bad. 170 doesn't seem all that hot. I will pull head tommorrow. seems to have a hot spot right at switch. thanks. S."
 
"head off today. no problems s

"head off today. no problems seen. anodes are even ok. head gasket ok. still don't think this is a flow problem. will remove exhaust cover just to cover all bases.
Got a call from local marina. C85TLRQ (92) same symptom. water pump new. thermo. new. poppit checked out and cleaned. same, same ,same . something about these models?"
 
Could this be a high speed ven

Could this be a high speed ventalation problem? I just purchased a Hyd. jackplate. I'm having to install a water pressure guage AND maybe a "Big foot nosecone" water pickup on my 115.
A water pressure guage is cheap diagnostics tool.
 
"Scott

Hope you got that 8

"Scott

Hope you got that 85 YAM fixed by now .IF not I ran into the same thing (symptons and I tried it all) changed thermostat ;popo off (bypass),waterpump,Waterpump press gauge stable and 18psi at wide open.Talkes to SONNY Marine in PORT Oconner tx.He asked if I had ever fished south of here esp during BROWN TIDE or RED TIDE.YES I had.Here is my best understanding of what happens .This brown /RED tide goes through your water passages and attachs itself to the block and head and grows .Not anything you can see but it coats the surface with a glass like coating .This makes heat transfer between water and (head and block)less causing the overheating at high speed.I pulled the head and water cover on it to expose passages,and taped (plugged) so you could fill the head passages with LYSOL brand TOILET BOWL cleaner.It foamed and did its thing for a couple hours .I washed it up and dried taped and then did it again for a couple hours. Soaked and washed it real good in tap water Dried Installed with new gaskets and torqued. Went fishing that was 6 months ago and never another alarm.They say its not only a YAM problem but all outboards . Hope this will help you or someone
DAN"
 
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