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Fgeo14

Alarm stays on for about 20 seconds

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I have a 2005 Sunesta 216 with a 5.0 TKS engine. After starting and stopping the engine a few times (to switch out kids while tubing)  the alarm stays on after the initial start but always goes off in about 20 seconds. All fluids are at the right level as well as the temp gauge reading is normal.

Any ideas?

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As the alarm is constant, my guess is that it's one of the exhaust manifold high temperature switches that is unhappy. They will not influence the helm engine coolant gauge reading but are still an indication of a localized overheat. When you shut the engine down, it goes into a period of heat soak, and actually gets hotter than when it was running. You may have a partially plugged manifold water jacket, or a weak raw water pump that can't keep up with this temporary high temperature excursion. After a hard run, allow the engine to idle for at least 30 seconds in neutral and see if the issue goes away, and also feel the top of the exhaust risers with your hand to see if one is hotter than the other. Look for discolored paint too.  A failing raw water pump impeller will cause this momentary overheat,  and a constant alarm will also be set if your raw water pressure sender is failing. The fact that the alarm is constant limits the possibilities to overheat, engine oil pressure, sea water pressure, and drive lube level.  W

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Thank you for this advice! How can I ascertain if it’s a plugged manifold water jacket, or a weak raw water pump?

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As it's an 2005, it's beyond time for the manifolds to be removed, inspected, and re-gasketed at the very least. A rust through failure there will likely result in water entering a cylinder or two through an open exhaust valve.  Localized heating at the top of the risers is an indication of internal restriction, but the only way to know for sure is a complete internal inspection. Look for differences side to side, and if one bank is hot to the touch and the other is REALLY hot to the touch, chances are you are in need of a good internal cleaning and inspection. When I do them I also rebuild the starter too as it will be easier to access with the manifold off. As far as the impeller goes, when was the last time it was changed. Merc says 3 years or 100 hours, which ever comes first. Even a brand new impeller can become damaged if you were to do something as simple as running over a trash bag, momentarily shutting off flow to the pump suction side. This is a common problem in metropolitan areas. You can install a hand held scan tool and read the real time pump discharge pressure, but that service call will be more than the cost of a pump impeller kit. I put a pressure gauge on my pump discharge circuit at the power steering cooler water inlet fitting so I can monitor impeller health in real time. 4 seasons seems to be the sweet spot for me but impeller replacement is different for every situation. At year 10 my shaft seal gave up so I replaced the bearings, seals, shaft, and impeller, and drive belt. My guess is your boat has an Alpha 1 Gen 2 drive system so your impeller is in the lower gear case of the out-drive and is easier to service than it's bigger Bravo brother.  W

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Thanks Wingnut. I did have the manifold gaskets replaced 4 years ago so I hope the tech also inspected them when doing so. I change the impeller every 2 years and just did it last year. Come to think about it this problem started to present itself last year. I’ll give them a light hand touch this weekend and report back what I find out.

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10 hours ago, Fgeo14 said:

Thanks Wingnut. I did have the manifold gaskets replaced 4 years ago so I hope the tech also inspected them when doing so. I change the impeller every 2 years and just did it last year. Come to think about it this problem started to present itself last year. I’ll give them a light hand touch this weekend and report back what I find out.

The "overheat senders" on the exhaust manifolds are nothing more than simple on/off switches that trigger at 220 degrees F. Your tech would not be able to detect an issue by looking at them. He could have used Teflon tape on them upon re-installation which essentially renders them useless by isolating their ground circuit, but that would prevent them from working, not set an alarm as they are a "normally open" switch.  W

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Wingnut, so I measured the temps of the manifolds using a thermometer gun and the post side was about 10 degrees hotter than the starboard. Enough of a difference or is it a water pump issue? 

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On 9/6/2019 at 7:57 AM, Wingnut said:

The "overheat senders" on the exhaust manifolds are nothing more than simple on/off switches that trigger at 220 degrees F. Your tech would not be able to detect an issue by looking at them. He could have used Teflon tape on them upon re-installation which essentially renders them useless by isolating their ground circuit, but that would prevent them from working, not set an alarm as they are a "normally open" switch.  W

Wingnut, so I measured the temps of the manifolds using a thermometer gun and the post side was about 10 degrees hotter than the starboard. Enough of a difference or is it a water pump issue? 

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10 hours ago, Fgeo14 said:

Wingnut, so I measured the temps of the manifolds using a thermometer gun and the post side was about 10 degrees hotter than the starboard. Enough of a difference or is it a water pump issue? 

As mentioned, the exhaust temperature senders are a simple SPST switch that is either on or off. They will set an alarm at 220F so it would seem your issue is elsewhere. My guess would be low raw water pressure sender is not always happy which is symptomatic of a failing raw water pump impeller.  I don't know the history of your existing one, but even a new one can fail if it ingests some sand, or you run over a floating trash bag. I'd start there as yours is easy enough to change.   W

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On ‎9‎/‎5‎/‎2019 at 9:03 PM, Fgeo14 said:

Thanks Wingnut. I did have the manifold gaskets replaced 4 years ago so I hope the tech also inspected them when doing so.

Do you remember him mentioning anything to you about the water jackets in the manifolds and risers if they looked good?  Or maybe you got a look at them?  If one is warmer than the other, then that one is probably not getting the proper flow as the other.  Changing the gaskets only means he must've been comfortable enough to not worry about the water jackets but I'm guessing he must've told you that (even fresh water used boats) that have exhaust manifolds and risers from 2005 will only last so long.  That's 14 years going on to 15.  I know they aren't cheap, but it might be a good idea to add that to your list of winter/spring maintenance and replace both exhaust manifolds and risers. 

I was going to do mine before this season, but a trusted member on here told me I could get at least another year or more out of them and he was right, so far (I hope they last through our last weekend which is the one after next)  but since I'm in salt water and they are starting to look pretty bad at the joints (leaking rusty water much more than last year) yet when I touch them after several hours of cruising (even at higher speeds), they're not super hot and one is warmer than the other, but those are definitely being replaced this year. 

On ‎9‎/‎4‎/‎2019 at 8:02 AM, Wingnut said:

Look for differences side to side, and if one bank is hot to the touch and the other is REALLY hot to the touch, chances are you are in need of a good internal cleaning and inspection. When I do them I also rebuild the starter too

How do you clean them?  long, wire brush and acetone? 

 

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On 10/1/2019 at 9:37 AM, Hatem said:

Do you remember him mentioning anything to you about the water jackets in the manifolds and risers if they looked good?  Or maybe you got a look at them?  If one is warmer than the other, then that one is probably not getting the proper flow as the other.  Changing the gaskets only means he must've been comfortable enough to not worry about the water jackets but I'm guessing he must've told you that (even fresh water used boats) that have exhaust manifolds and risers from 2005 will only last so long.  That's 14 years going on to 15.  I know they aren't cheap, but it might be a good idea to add that to your list of winter/spring maintenance and replace both exhaust manifolds and risers. 

I was going to do mine before this season, but a trusted member on here told me I could get at least another year or more out of them and he was right, so far (I hope they last through our last weekend which is the one after next)  but since I'm in salt water and they are starting to look pretty bad at the joints (leaking rusty water much more than last year) yet when I touch them after several hours of cruising (even at higher speeds), they're not super hot and one is warmer than the other, but those are definitely being replaced this year. 

How do you clean them?  long, wire brush and acetone? 

 

Yep, thats how it done!!

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