port engine alarm

Speedracer1972 · Aug 7, 2024

we have a 2007 320 Sundancer.

This past weekend my wife and I attempted to go out on the waters of the Chesapeake. Once we were out of our slip and I applied trust to the engines I had a piercing alarm come on. I pulled back on the throttles and the alarm went away. Trying to isolate the issue I pushed the port engine throttle forward and the alarm returned. Pulled back on the throttle and the alarm went away. Tried the same for the Starboard engine but no alarm. Looking in my Vessel View app it told me "Water pressure in the cooling system is low" Obviously we returned to our slip. Several hours later, once they cooled down I checked the water level in the heat exchanger and it was as full as can be. I aslo looked at the coolant recovery bottle and while the level seemed low, it was about an inch above the "add" line.

I am not the most technical person when it comes to engines and being on the larger side it is hard for me to do anything in the engine compartment of that boat. So after calling several mechanics, none of which could see see me for several weeks I got the thinking. The boat had sat in the slip for about a month without us taking it out. So i was thinking there might be some growth on the raw water intake grates. So I scheduled my marina to do a short haul to power wash the growth off. The night before it was scheduled to come out I went back, wanting to reproduce the issue in the slip without taking it out. I was unable to do so. i let the engines warm up to normal temps and then, without them being in gear, ran the throttle up to about 3000RPM. The alarm would not come back on.

The attached pics are what the marina sent me once the boat was on the lift. I felt confident that my issue would be resolved, but to be safe we took the boat out of the slip that night to test to verify all was good. The alarm came back on.

So now i am thinking there is growth behind the raw water grate that the power washing could not get or the water pump was died after 17 years.

Are there way to isolate the issue before i start spending money on parts, haul outs or mechanics? The pump alone appears to be about $500, while I have no issues spending that money if that will fix the issue, i do not want to buy it, put it in and the alarm to come back on.

any help would be greatly appreciated.

garybly · Aug 7, 2024

You can hire a diver to clean bottom rather than pull it out of the water, that's what we do in Fl. 100 every 2 months is what I pay and every month in the summer when marine growth is more of a problem

Speedracer1972 · Aug 7, 2024

thanks. I will look into that. I knew that was an option, but i expected it to be more expensive. the short haul, with the marina taking it out of the slip and back in cost be almost $600

Jimmy Buoy · Aug 7, 2024

You were checking the coolant (antifreeze) levels, but there are two separate parts to your engine's cooling system. The antifreeze part is circulated through the engine block by the engine's circulation pump (on the front of the engine) and back through a "cooler" to remove the heat. From there, it goes back to the engine block and round and round it goes. That doesn't seem to be your issue.

The cooler has raw water from under the boat pumped through it by a belt driven raw water pump. The water is then flushed out with the exhaust as new water is constantly being pumped from under the boat to the cooler.

If the raw water pump cannot draw sufficient water from under the boat due to restrictions (like the growth on your raw water intake grate) it will be unable to provide adequate flow of cool water to the cooler. Merc has a water pressure sensor in place to alert you of such an issue to prevent overheating the engine. The alarm has done its job to protect that from happening. There's a slight chance that the rubber impeller in the raw water pump was starved of water long enough to overheat it and cause damage, but its more likely that it still had enough water to avoid damage - just not enough to keep the water pressure sensor from triggering.

The restriction on the outside should be clear now, but there could be a blockage on the inside. It might be more likely that some debris from the initial cleaning has gotten stuck in the sensor. I'd remove the sensor and screw in a clear tube where it goes, start the boat up and see what kind of flow you're getting from the raw water pump. Also, the boat does not have to be out of the water to work on the raw water pump or the sensor.

port engine alarm

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