Classic AquaSport
Aquasport Mechanicals - things that need a wrench, screwdriver or multimeter => Engines & engine woes => Topic started by: 610Ved on September 11, 2019, 11:46:59 PM
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Recently my overheating alarm has been going off on my 2001 Yamaha 90 2 stroke. I know it's not the thermostat and temp sensor because I can feel the heads physically overheating (not able to keep my hand on them). Motor has been flushed every time since I purchased the boat back in February and the only issues have had with it was a bad fuel pump. Until now it's been running great. When run on the muffs the motor overheats and I suspect the water isn't reaching the heads. I went to use the flush port with cold hose water and immediately the motorhead is much cooler to the touch after about a minute. This and the fact its peeing strong leads me to believe the water passages are fine.
My first suspect was the water pump so I currently have the lower unit taken apart and the impeller seems to be in good shape with no cracks or breaks. However, after watching a video on how to take the lower unit off and looking over the service manual and parts lists it hit me that an entire hose set is missing from my lower unit. I'm guessing this is a big issue I know what parts I need, I just can't figure out where the hose connects into the topside of the motor.
Missing hose and parts (in red)
(http://www.classicaquasport.com/gallery/data/500/InkedLower_unit_assembly_LI.jpg) (http://www.classicaquasport.com/gallery/showphoto.php?photo=19217&title=inkedlower-unit-assembly-li&cat=500)
Where this hose should be
(http://www.classicaquasport.com/gallery/data/500/120.jpg) (http://www.classicaquasport.com/gallery/showphoto.php?photo=19214&title=120&cat=500)
Impeller
(http://www.classicaquasport.com/gallery/data/500/220.jpg) (http://www.classicaquasport.com/gallery/showphoto.php?photo=19215&title=220&cat=500)
Water pump housing
(http://www.classicaquasport.com/gallery/data/500/314.jpg) (http://www.classicaquasport.com/gallery/showphoto.php?photo=19216&title=314&cat=500)
If anyone can post a pic of how this connects or where I should be looking I would greatly appreciate it.
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The part you have circled is the speedometer tube, which plays no role in the cooling system. However, by the looks of the LU color brown there is water entering thru the speedometer water inlet dumping into the mid-section. If you dont intend to use a speedometer gauge then seal the connection where the tube inserts.
That's probably the reason you're seeing stronger flow from hose connector vs muffs. But I'd definitely replace the kit while you're in there. Gaskets look terrible.
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Thanks for the insight, I was super confused. Replacing the kit was the plan all along. I'm not running a speedometer so I'll just plug it up and clean out all the gunk in the lower unit. Hoping the water kit replacement ends my overheating woes.
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That impeller has enough set in it to cause overheating at idle or trolling.