Seawater Flow check

[scottzorn]

Hello, I am helping my dad get his 28' Albin back in the water after 2 years in dry dock in Anecortes, Wa.

Boat & engine have been well maintained and all seems to work well, although I am getting an intermittent "Low Seawater Flow" alert. I have only had the boat running at the dock for about 20 minutes and the alarm was going off every coupl of minutes, but just for a second or two and then off again for a minute or two. I haven't run the boat in open water yet, but am hoping to this weekend for a few hours.

So the questions are:
1) Does anyone have any advice for troubleshooting this? I assume there is a ball valve or petcock somewhere I can check to make sure it is open
2) assuming that checks out, is the next step to call a mechanic to come out and look at it?
3) is it safe to run for an hour or two with intermiitent warning light? (could running it in open water be what it needs to get water flowing?)

I'm planning on having the boat serviced in September, but am hoping to get my dad out a few times while the weather is still nice. So any and all feedback is appreciated. I don't want to take it out at all if this sounds like a major issue that needs to be serviced before any use at all.

[Norseman]

If you have the Yanmar engine there is a flow sensor on top of the engine at or above the intercooler.
On my boat the sensor was worn down, I replaced it and problem solved.
It could of course also be a real flow problem on your boat, check for rat nests in the cooling system or other obstructions caused by the boat sitting on the hard for 2 years, like the water pump worn or damaged.
(On the Yanmar it is under deck almost invisible on the Starboard side. Get a new pump for $500 and have the old one overhauled so you always have a spare.)

[Tree]

It is the shaft on the sensor - they wear away over time and don't allow the float to lift when sea water is flowing.

Apply some RPM to the engine out of gear and see if the alarm goes off.

They cost around £180 here in the UK so i have just unplugged mine for the time being.

[Norseman]

. They cost around £180 here in the UK so i have just unplugged mine for the time being.

Jeez, expensive flow sensors in the Uk.
Perhaps cheaper in the EU, Like France… ?

[carolmarie]

I have a Yanmar. To my knowledge there is no such thing as a Low Seawater Flow alarm. Seems to me that such an alarm would indicate low water flow through the primary seawater filter due perhaps to some short of blockage or a raw water impeller that may have taken on a set and not passing sufficient water flow. In any event, either of these conditions should result in a high engine temperature alarm.
The sensor/alarm that Norseman referred to, I believe, results in a high exhaust temperature alarm due to ware. Higher RPMs usually shuts the alarm down if that sensor is the issue; the sensor needs to be changed.
Don.

[Tree]

Don, it’s the square bolt like thing on the top of the intercooler - two wires coming out of it. They took them off later yanmars because they fail so often.

[RobS]

Intercooler end cap with seawater flow switch

12.JPEG

Internal view of float assembly:

11.jpg

Later production 6LP with the flow switch port plugged (next to zinc and inline with seawater hose):

02.JPG

[Carl]

2 years on the hard, I would start with new impeller in the sea water pump.

[RobS]

For sure

[scottzorn]

Thank you all for the quick response to this questio0n! I have to say, I am super impressed with the speed and knowledge in responses. I am not used to that on the internet which is usually fast but poor quality, or slow and high quality. This Albin group my be the pinnacle of fast and smart!

I tested the engine in neutral and higher RPM and the alarm quits going off. I didn't do it for a long period of time, but it seems consistent with the theory that the sensor shaft may be worn. causing the float to stick.

Just to be safe, I am going to try to get the mechanic who works on the boat to swing by if possible to confirm. If it turns otu to be anything more interesting, I will be sure to follow up with details and pictures if I can. Thanks again, I really appreciate the feedback.

[rhutch98]

I think my sensor has gone bad as well, was at about 3000 rpm and I backed down to 1000 to come off plane when the alarm triggered. I immediately turned the engine off and did some mid sea trouble shooting. I pulled the water pump and the impeller looked good but I replaced it anyway. Started back up but the alarm still gong off. The water flow out the back was normal so disconnected the buzzer to trouble shoot further. All temps (water and exhaust) remain normal so I proceeded with my journey. The alarm light would would come and go for the rest of the trip so I am convinced it is the sensor, so I have ordered a new one. What’s the best tool for removing the square sensor?

[rhutch98]

Well, I guess I can answer my own question on the right tool. I used a 15" crescent wrench and that did the trick although it was likely overkill.

So does anyone know how this sensor actually works?

While waiting for a new part I did some tinkering. I assumed that the disk would float to the top when the water is moving through but manually sliding up the disk still leaves my alarm light on. Also I placed it in a cup of water and noticed that the disk doesn’t actually float. I can see shaft is quite worn, I can see the wires in the middle in a spot so my guess is this thing is toast but I do wonder if my engine has digested some of it since it does not actually float in water and moving it up the shaft does not clear my warning light.

[Patrickgoggin]

Sounds like the sensor is bad. The disk should float and change signal when moved from the low end to the top. It can be checked with an ohmmeter.

Separately the alarm light can be checked by disconnecting from the sensor and either leaving it open or sending it to ground. I think that when it is grounded the light will go on and when it is open the light goes off (would need to verify with the wiring diagram).