Yamaha Overheating - Could Use Some Help

Discussion in 'Boats, Blinds, & Gadgets Forum' started by smashdn, Dec 4, 2020.

  1. smashdn

    smashdn Elite Refuge Member

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    Got it out. Ran the crap out of it. Runs wot like a dream. Come off pla

    ne and idle about 3mph and it will overheat. Will overheat on courtesy dock if allowed to run 5 mins or more.it doesn't do it as often but still get the alarm
    In those c
    ircumstances.
     
  2. smashdn

    smashdn Elite Refuge Member

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  3. Phytoplankton

    Phytoplankton Elite Refuge Member

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    Get a can of engine tuner, you spray it into the carb until it almost dies. Then you let it sit overnight fire it up again, it will smoke like a house on fire, that’s the carbon burning off. There will black spot coming out the exhaust. Just follow the directions on the can, there’s several brands with slightly different directions. You will need to replace the plugs when you’re finished.
     
  4. Phytoplankton

    Phytoplankton Elite Refuge Member

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    I should add, even if you run ring free in every tank of gas, you can get carbon building up. Normally it collects under the rings, if enough of it builds up it will not allow the rings to dissipate heat and eventually the ring(s) will grab the cylinder wall and break, the piston will "trip" over the ring and trash the block. It can also build up on the cylinder head I've seen it happen numerous times, even had it happen to me, but I was lucky when my rings grabbed the cylinder wall they didn't break, just locked up the block. After a couple minutes the rings released with no damage, limped home and de-carboned. Engine has run great since then. I try and de-carbon my engines every year or two depending on use. BTW, it's normally not an issue with 4 strokes.
     
  5. markd

    markd Elite Refuge Member

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    How can you tell if it is really getting hot or if maybe the sensor is bad? What if you picked up one of those infrared grill/auto thermometers and got a temp off the block when it was on plane with no alarm, then in the same spot again when the alarm went off. Maybe, there isn't a problem with the actual motor. Something like this (example, I have no experience with it).....

    https://www.amazon.com/Klein-Tools-...ocphy=9007556&hvtargid=pla-942862716849&psc=1
     
  6. captbil2003

    captbil2003 Refuge Member

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    Had same problem years ago on Yamaha 60 how 2 Stroke, turned out to be temp sensor, 5 min fix
     
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  7. smashdn

    smashdn Elite Refuge Member

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    Temp sensor is new. you test function with voltmeter on ohms and place sensor in pot of water on stove with thermometer in it. the resistance changes when you hit the temp sensor set point.

    I put an ir thermo on it. Top cylinder is hot around 180f.

    Got to think either water isnt pushing hard enough into top of jacket or carbon. i might fiddle with it tonight. Put it on muffs.
     
  8. Phytoplankton

    Phytoplankton Elite Refuge Member

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    Carbon isn't going to cause that. A weak water pump, bad/incorrectly installed thermostat, or obstruction in the water passages will cause that. I don't know that engine well enough, can you pull the water jacket and see if it's obstructed? One last thing, is the intake screen clean?
     
  9. JFG

    JFG Elite Refuge Member

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    After reading all this, it appears to me you have a blockage in either the water tube passage as it enters the engine or the water jacket itself within the engine. I had a similar issue …engine ran, peed great but would start getting hot when idling. I did just about everything you did (new water pump/housing, therm, etc.) to no avail. Finally called experienced mechanic and he told me problem was most likely passage at tube was blocked just enough to not get “enough” water circulating at idle. His least expensive fix was to cut water tube just before entering engine block, then taking a 1/2” drill bit and reaming the passage out. Afterwards, he basically spliced the two ends back together with a short piece of hose and 2 clamps. Worked like a charm, no issue in year and half and I use boat year round. He told me this was a common issue in older motors (mines a ‘97-50hp 4-stk.) and he’d fixed countless engines this way. He actually said he’d walk me through it if I wanted to do it on my own but I was frustrated enough by then to just take it to him. After seeing what he’d done, it was a simple job. It doesn’t take much build up in that passage to cause it to overheat. You’re getting water through it, just not enough.
     
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  10. smashdn

    smashdn Elite Refuge Member

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    I pulled the head and exhaust plate and scrubbed them. Intake screen was removed, cleaned and reinstalled. Blew compressed air both directions through water tube up into engine and down back through.

    Temp sensor, thermostat, head and exhaust plate gaskets, impeller and impeller cup, water pump gaskets are all new.

    I can try to snake a small bore brush up the water tube to scrub it.
     
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