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496 exhaust overheat

Old 07-10-2017, 03:31 PM
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Originally Posted by actionmarineguy
crownline single engine all readings with computer and verified with heat gun both are pretty close changed pressure sensor it was off Now water pressure at is around 2.5 at idle At 3500 goes up to 4 at 4000 goes in guardian mode emct overheat runs 3500 all day engine temp never goes up.
You mentioned an impeller change. Was pump assy changed or impeller changed in original housing?
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Old 07-11-2017, 08:58 AM
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Thanks for the suggestions working on it today. only merc parts used . curious about end cap gaskets they were sealing but deformed What is the huge problem?
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Old 07-11-2017, 09:08 AM
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You wouldn't think it would cause a problem, but BUP fixes these for a living, then comes on here and diagnoses problems for free. I haven't seen him wrong yet.
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Old 07-11-2017, 10:39 AM
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Originally Posted by actionmarineguy
Thanks for the suggestions working on it today. only merc parts used . curious about end cap gaskets they were sealing but deformed What is the huge problem?
The deformations can block the tubes which are imperative to your cooling.
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Old 07-11-2017, 07:06 PM
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Thanks for the good words about me.

The jist -- the heat exchanger end cap gaskets not only deform they grow bigger in which blocks the water hoses connection outlets from the heat exchanger to the exhaust manifolds -- If you pull those hoses off from the heat exchanger - water will drain - then stick your finger up in there if you feel any rubber, your end cap gaskets are blocking the water flow to the manifolds. Also these are maintenance items of 5 year - then change out with new gaskets.. I am telling you as they should be changed regardless every 5 years or less or if you over heat the engine. Those gaskets are week - the end cap gaskets.

Any cooling water that can back up --- causes the water pressure to drop. Not saying this is your exact problem for low water pressure and those readings --- but I would NOT RULE IT OUT EITHER.

A lot of times the WPS itself, the hole has a bunch of junk in it or the WPS goes bad or restrictions to impede water flow or the impeller is weak or the impeller and impeller housing is the issue. GEN VII water pump housings are NOT that good for lasting - they scar very easily. This causes low water pressure as well.

Last edited by BUP; 07-11-2017 at 10:08 PM.
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Old 07-12-2017, 11:06 AM
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Thanks to all. 'Fixed'' main problem was intake hose where it goes through transom. Corrosion around outside of hose crushed the retaining nut in the center of hose. I could not get a pencil through the opening. also changed end cap gaskets on heat exchanger.
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Old 07-12-2017, 04:04 PM
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Originally Posted by actionmarineguy
Thanks to all. 'Fixed'' main problem was intake hose where it goes through transom. Corrosion around outside of hose crushed the retaining nut in the center of hose. I could not get a pencil through the opening. also changed end cap gaskets on heat exchanger.

496 brass gen 7 water pump. gre 7 repair kit for badly damaged pump body. If your brass body is badly grouved and fails to pump. our kit makes pumps work again without buying new pump. Rubber Impellers W/P Mercruiser Impeller Repair Kit $24.95. IMPEL

bottom of page,,works great
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