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Discussion Starter · #1 ·
I have another topic.
4.3 Merc V6. If looking at the engine from inside the boat. My buddy has one and it runs always warmer on the right bank. I told him that its because of the steering cooler being connected to the right bank. I know 4.3 have the main drive water impeller hose on right side also. He runs a cool 140F thermostat and boat never over heats. When on cold water muffs it idles and seems cool to touch on bolth sides. When you run under load on the lake and put your hand on the right bank you can tell that right is hotter then left but still bolth sides can be touched with a palm of the hand for a sec or two.He has a 17Ft Sea Ray BowRider. What you guys think?
 

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Discussion Starter · #4 ·
Well actually Chase Bank


Anyway for all that have same problem or ever wanted to know why one side runs hot here it is. So I went to a local boat shop and a guy explained that its normal for one side to be warmer then the other. Its because of water flow,impeller wearing out and main important reason some blocks hold more water on one side then the other. GO FIGURE WERID. SO COOLING IS ALWAYS POSATIVE TO ONE SIDE.
 

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My 502 always runs slightly hotter on the starboard side. I've been told it's normal.

I believe the stock thermostat in these things is 140 or 145. My boat usually runs in the 160 range.

I don't have any steering or oil coolers attached to either bank. They are both in the water flow path from the seawater pump to the engine. Impeller wear won't bias water to one bank or the other either. It just has to do with where the water comes in and the design of the cooling system - these are old engines, designs adapted from car engines, the cooling system just wasn't designed to properly balance water flow side to side.

Also, keep in mind that when you're checking which side is hotter, all you're looking at is the exhaust. The actual cylinders are going to be closer to the same temperature.
 

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I've always read its due to plumbing run lengths and inline cooler positions that will cause fluctuations side to side per motor AND fluctuations Port to Stbd.
 
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