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How hot is to hot

Old 08-29-2009, 08:48 PM
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I have been running my boat for the summer and the temps have been at about 150 degrees all summer. Last evening I ran up for dinner with some friends and the boat was running at about 180-190. The water temp this week was warm (about 78-80 degrees). Is it the warm water temps causing the problem or do I maybe have another issue to look into. These are 420hp 454's and they both are kind of doing the same thing. The temp held steady no matter what speed I ran.

Jon
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Old 08-29-2009, 09:25 PM
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Do you have the Merc 143 degree thermostats? My 454 370 HPs used to stay dead on no matter what the conditions. I wonder if you flow is restricted or maybe your impellors are weak. Are both engines the same? Any changes to the original Merc water system?
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Old 08-29-2009, 09:58 PM
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Those should hold temp no higher than 160* with the 140* tstats.
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Old 08-29-2009, 10:08 PM
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New water pumps this year and they are both doing the same thing. They just started this yesterday. That is why I was thinking the lake water was so warm causing this. Everything is totally stock.
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Old 08-29-2009, 10:15 PM
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Jon, change the controls, that is t-stats. be sure your flow is good and be sure your sea strainers are clean. say hi to Kurt.
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Old 08-29-2009, 11:43 PM
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My engine water temps never changed at all in my 525SC, no matter what the lake water temp was. Idle and cruise was around 145* and WOT was just under 160*. It had the same cooling system as the 420.
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Old 08-30-2009, 06:29 AM
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I will try and get some time today to take a look at it. I just find it so odd that this happened all of the sudden and with both engines.
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Old 08-30-2009, 08:38 AM
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Are those engines fresh water cooled? I dont think the water temp being maybe 10 degrees warmer then normal would account for a 30 degree variation in running temp. As others have said I would check your flow rate starting with the strainers and the impellers

Jim
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Old 08-30-2009, 10:09 AM
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They are raw water cooled. I am going to dive into the water today if I have time and check and see if the water pick ups got clogged with weeds then work my way from there.
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Old 08-30-2009, 08:35 PM
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78-80 degree water in Mass? must be a record!
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