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Dominick
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 2003 Sea Ray 240, with Mercruiser 496 Mag Bravo

Customer Question

Hello, I have 2003 Sea Ray 240, with Mercruiser 496 Mag Bravo 1, with the SmartCraft monitoring system.
The boat has recently had a lot of regular maintenance done, including new water pump housing, impeller, plugs, coolant, lower drive lube, etc. and has been run several times after with no problems. All fluids are full.
On my last trip out, I started getting a solid alarm from the monitor, that is cutting power and won't let it go above idle, however, none of the reasons I've read this happens seems to be occurring.
From my research, there are five things that can cause a solid alarm, reducing power:
Coolant Over Temp (Nope, temp never goes over like 165, and alarm comes on much sooner.)
Low Oil Pressure (Nope, well over 50.)
Exhaust over-temp (???)
Sea Pump PSI Low (2.5 - 4 psi at high idle, seems fine)
Engine over-speed (Nope)
The alarm comes on a few minutes after a cold start, which would seem to indicate a heat issue, but using my infrared thermometer, the exhaust risers never got above 113F, and you can place your hand on them without discomfort. I'm getting water sputtering out the exhausts outlets.
Oil pressure, engine temp are fine, and sea water pressure seems fine, although this is one I'm least familiar with. It's around 2.5 PSI at idle, like 4 PSI of I high idle. Haven't checked after the alarm came in at higher RPMs. Like I said, new pump housing and impeller.
Any ideas what could be causing the solid alarm? Of the five things that can cause this alarm, all seem to be fine. Could one of the exhaust temp probes be picking up a high temp I'm not seeing on the riser?
Any help appreciated.
Submitted: 1 year ago.
Category: Boat
Expert:  briggs archer replied 1 year ago.
The answer is yes. If you are reading the temp on a computer scanner at 200 deg an alarm will sound. The water temperature Sensor on the manifolds could be faulty. But consider this; If a water flow restriction only supplies enough water to keep the engine cool but not the exhaust manifolds then an alarm would sound.The water pressure is good at 2.5 psi but you should get up to 9 psi at high idle. Before you purchase manifold sensors check the inlet hose at the transom. It is hard to get to but may be restricted there, due to corrosion squeezing the hose smaller.

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