Engine randomly throws errors and shuts off

[robertpel9]

Hello
I have a 2008 38 sundancer

randomly every 5th trip or so the starboard engine will shut off. my display will say wither low voltage OR low water PSI

i had the batteries checked and they are fine and 2 years old. boat is used regularly, i also had the cooling system all checked out, replaced impellers as well at water pressure sensors

nothing helps

mechanic is at a loss

my PSI shows high i think for both engines

at 3800 rpm it is 32psi at port and 18 at starboard. i dont believe either of them. visual inspection of exhaust outlets shows healthy and equal pressure. engines run at 160 to 165 all day

if i turn the engines off then go down to the panel and turn engine battery off, turn both keys off then turn everything back on, everything works just fine until it happens again, and who knows when that is, could be days

any ideas

 

[PlayDate]

Does your mechanic have access to another water pressure sensor? Swapping them between the engines is a quick way to determine if it is the issue.

 

[robertpel9]

Does your mechanic have access to another water pressure sensor? Swapping them between the engines is a quick way to determine if it is the issue.

He replaced both sensors with brand new ones. The result of that was the port engine still shows about 32 psi when at 3800 RPM. The starboard engine, which was typically around 18 had gone all the way down to eight or nine. After replacing the sensor it came back to around 18

I don't believe these readings are even correct even with brand new sensors. If I recall correctly, it shouldn't they be running in the teens when at this rpm?

In any event, both sensors are new. Both impellers are now. The risers have been inspected and are fine. The coolant was just changed and again this is very intermittent. I can take it out for hours three or four times and it will be perfectly fine. Then the fifth time it will just shut the engine down and I either see low voltage or low water PSI on my Furuno display along with a beep

 

[scoflaw]

OEM sensors? Cheapo's are known for that.

 

[robertpel9]

OEM sensors? Cheapo's are known for that.

Yes.new
OEM

First it shows a quick low voltage morning and then low PSI but the PSI is fine. When it's running after it gets the low voltage warning then it gets low psi it seems. Then if I just reset everything everything starts right back up and works fine. First, we switched sensors from one side to the other. It may no difference so we replace both sensors with new factory ones

 

[PlayDate]

Generally and others will weigh in ....it is in the high teens at that rpm (starboard @ 18psi is what I would expect). The 32psi on the port is really high which could be a blockage if it is really that high. What's weird is that the temp is okay. If it was a blockage....the temp on the port engine should be rising.

I would definitely put an analog gauge on the hose to see what the real pressure is. If it is really 32psi it is time to start looking for blockages possibly in the heat exchanger. For your mechanic.....any pressure gauge will work if it has a 0-30 psi range. Check both engines and you should have your answer.

If it is normal then you are back to the sensors being bad or an issue with the wiring/connectors.

 

[robertpel9]

Generally and others will weigh in ....it is in the high teens at that rpm (starboard @ 18psi is what I would expect). The 32psi on the port is really high which could be a blockage if it is really that high. What's weird is that the temp is okay. If it was a blockage....the temp on the port engine should be rising.

I would definitely put an analog gauge on the hose to see what the real pressure is. If it is really 32psi it is time to start looking for blockages possibly in the heat exchanger. For your mechanic.....any pressure gauge will work if it has a 0-30 psi range. Check both engines and you should have your answer.

If it is normal then you are back to the sensors being bad or an issue with the wiring/connectors.

Will do and thank you. My follow-up question will be what would any of this have to do with the low voltage warning I'm getting on that same starboard engine everything's on the starboard engine which is the one with the proper PSIs. That's the one that shuts down. That's the one that gets all the warnings. The port engine just keeps rolling along

Temperatures on both engines are rock solid once warmed up between 160 and 165

 

[PlayDate]

The low voltage is usually a wiring/connector issue. As @scoflaw notes we have seen a lot of weird things show up in replacement psi sensors.

The analog approach will give you a baseline that: 1) gives you confidence things are actually okay 2) moves to the next stage of sorting out the voltage anomaly which is usually a connector/bad ground/wire. Those are a bitch to trace because the low voltage may or may not be related to the sensor itself.

I would start with cleaning the connectors that connect the sensors and cleaning the engine multipin connector as well with an electronic cleaner.

Disregarding the port 35 psi for a moment......what you are experiencing every 5th trip or so seems like a loose connector/wire. Turning everything off and then back on where it works again also fits that issue.

 

[scoflaw]

Agree with that, voltage drop from a bad connection will throw that code.
Your sig shows a diff. boat, What engine in that 38?

 

[robertpel9]

Agree with that, voltage drop from a bad connection will throw that code.
Your sig shows a diff. boat, What engine in that 38?

Twin 8.1s

 

[scoflaw]

Your engine dying from another unreported condition could easily throw those 2 codes as the rpm's decrease.
Fuel problems won't throw a code. If this happens at idle it could be an IAC, these can fail with no code.
That PCM has a lot of info and system checks, freeze frame data etc, you'll need a scanner.

 

[robertpel9]

Your engine dying from another unreported condition could easily throw those 2 codes as the rpm's decrease.
Fuel problems won't throw a code. If this happens at idle it could be an IAC, these can fail with no code.
That PCM has a lot of info and system checks, freeze frame data etc, you'll need a scanner.

Okay it only happens at high RPM. I'm going to say it happened above 3,200

If I get the dealership down there with a scanner should there be history codes of what happened? And my boat is in Newport Beach and it takes a good half hour to get from the harbor out to the ocean. So it's quite the undertaking to get it into waters where I can replicate the running conditions for a mechanic

 

[scoflaw]

Lots of self checks and Freeze Frame data to look at before you even leave the dock. Sound like a fuel problem now, have a pressure gauge on the fuel rail if you take it out.