Today I had a 'why do I bother' moment, as my (raw water cooled) engine continues to overheat on the muffs in my final boating days before I have to travel for the summer. I posted a thread before, and I thought I had the problem solved by expanding the springs of the checkballs in the thermostat housing (see image).
I tried the trick again. I tried removing the checkballs. I tried removing the thermostat. When I remove a hose to check flow, water appears to be circulating just fine - everywhere. [Edit: background: The boat had this problem on my first run, then 'fixed itself', and ran fine the rest of the day. After fiddling with the checkballs before, I launched and the engine ran fine for two days. I have replaced the impeller and housing]
I did notice that when I disconnect the hose going from the checkballs to the starboard elbow, water flows back toward the thermostat housing under pressure from the exhaust - I don't know if that is normal.
The engine was rebuilt 14 hours ago. They are the original manifolds, but the boat lived its whole life in fresh water. If I run out of ideas, I'll have to remove the manifolds. Could it be the temperature sender? Is there a way to test it, or should I get an IR temperature gun? How could the engine be overheating when water is flowing through the block?
Attached files [img]/media/kunena/attachments/vb/707697=30052-mercruiser_87-89_454_thousing_new.jpg[/img]
I tried the trick again. I tried removing the checkballs. I tried removing the thermostat. When I remove a hose to check flow, water appears to be circulating just fine - everywhere. [Edit: background: The boat had this problem on my first run, then 'fixed itself', and ran fine the rest of the day. After fiddling with the checkballs before, I launched and the engine ran fine for two days. I have replaced the impeller and housing]
I did notice that when I disconnect the hose going from the checkballs to the starboard elbow, water flows back toward the thermostat housing under pressure from the exhaust - I don't know if that is normal.
The engine was rebuilt 14 hours ago. They are the original manifolds, but the boat lived its whole life in fresh water. If I run out of ideas, I'll have to remove the manifolds. Could it be the temperature sender? Is there a way to test it, or should I get an IR temperature gun? How could the engine be overheating when water is flowing through the block?

Attached files [img]/media/kunena/attachments/vb/707697=30052-mercruiser_87-89_454_thousing_new.jpg[/img]
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