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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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I have twin inboard mercruiser 5.7 inboard with closed

Customer Question

I have twin inboard mercruiser 5.7 inboard with closed cooling system...I am having a high speed overheating issue on both..high temp is within a couple of degrees on both of them..I am seeing air bubbles in my sea strainers..xould this be causing the problem..I have done a water flow test and I have have plenty of water coming out of raw water while at the dock
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Customer: I have remove all hoses and checked for any blockage..engines have new intake manifolds and new fresh water pumps..raw water impeller are also new since being put into the water.
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Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello. My name is Tan.

Air bubbles will cause overt. The bubbles in the water will actually cause the water to boil.

Check the seals on the sea strainers. Is the bottom of the boat clean? Any kind of growth in the pick ups will cause aeration.

The other thing that will cause over heat at high rpms are restricted risers and a scaled up heat exchanger.

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