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Audible alarm on my Volvo Penta 50 GI

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gjgonzalez

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"My Volvo Penta 5.0 gi in my 2

"My Volvo Penta 5.0 gi in my 2000 Larsen has an audible alarm which I believe to be because of the cooling system, but eveything seems to be OK with it. I checked the impeller but it was OK. I also flushed things out in case of debris, but I still get the alarm and the rev limiter kicks in and won't go over 2500 rpm (or less). It's never seen salt water, everything is in very good shape. Any idea's?"
 
"you may want to start it up t

"you may want to start it up to run and if and when the alarm goes off you can start pulling off leads off your sensors ie. exhaust manifold overheat, oil flow switch, etc etc to see which one is causing the fault and then you can go from there to further diagnose"
 
Alarm and ECM are also impacte

Alarm and ECM are also impacted by low oil pressure and the ECM will go into default mode and hold to the rev limit you are experiencing. The Engine Protection Mode temperature fail safe kicks in around 2500 rpm. I think it triggers the ECM around 195- 205 degrees. I would perform normal cooling troubleshooting as your engine should be running in the 158-194 degree range and gauges aren't always accurate indicators of the true temperature.
 
"Having no luck with the optio

"Having no luck with the options offered up by you folks, not sure whats up still. It all started when I warmed the motor uo to change the oil and filter. Everything went as planned, Started it up again to make sure of no leaks, there was not, It ran fine until it reached it running temp and alarm went off and rev limiter kicked in. I check the impeller, it was fine. I changed the thermastate and installed it. Now the alarm start immediately and I don't have the chance to check all the sensors. I did get to the temp sensor and manifold sensor but neither shut the alarm. Is it tied into the fuel system also? Not sure were the sensor is for the pressure on it, but it has cansiter and a few other parts for the fuel pump which probably has to do with the injection system pressures. ANy other ideas?"
 
"fuel issuses usually dont sen

"fuel issuses usually dont send out an alarm. the oil flow switch is located on the port side of the engine right above where the oil filter would be on the block there will be one single wire going to it under the #7cyl. if this sensor gets a bubble in it and doset let the oil flow into it, or is failing, then its basically telling the engine that there isnt any oil pressure. its an on/off switch. do you get good oil pressure on your gauge. if so then this oil flow sensor might be going bad. there should be one overheat sensor in each of the exhaust manifold elbows. while running try pulling thoes off to see if an overheat sensor might be bad."
 
Ditto on Jarrod's comment

Ditto on Jarrod's comment around the OP switch located by the OF. I should have elaborated on my previous post as that was the cause of my alarm issue. MY OP was in range both on the electric gauge and a manual gauge that I installed. I ran a test on the OP switch and it checked out but I decided to change it out and that solved the issue. When I took the switch apart I found dirt so it line was probably partially blocked.
 
"I ruled out the oil sensor be

"I ruled out the oil sensor being the problem. I also know that I'm getting flow to the top of the engine and that there are no leaks. Having said that, back to the cooling system, I replaced the thermostate, I checked the impeller and thats fine, I disconnected the sensor at the thermosate housing and that didn't work either. I suppose it could be the water pump, but I know I'm getting flow through the engine and out the prop, plus I can feel the hoses and detect the water flowing through at low RPM and at 3000 RPM As for the manifolds, unless I am missing them, I don't see any sensors for them. I've looked all around them and I looed in the service manual for the cooling system and I don't see that they list them either. Could I be missing them?"
 
is this alarm constant? is it

is this alarm constant? is it faint? what year is the engine? the exhaust manifold sensors are on the transom side of the exhaust riser "elbow" the wire is in some looming but i think the wire is tan with black. it is a single lead. as far as i can remember all of the non aq volvo pentas have these sensors on the exaust manifold risers. does the alarm sound with the key on and engine off or only while running?
 
"Well the alarm is audible wit

"Well the alarm is audible with the motor running so it's not faint. It is constant, when you turn the key to the on position, not turning the motor over it give two beeps and the alarm goes off as well and then quites along with the beeps. Then, when you crank up the motor the alarm immediately starts up with the motor but runs fine until it gets to running temp of about 160-170 and then the rev limiter kicks in and the engine wants to die, you can keep it going by reving it up, but it doesn't like it, it can idle as long as it's not going over about 2000 rpm. It's a 2000 volvo penta 5.0 GI with EFI and a SX out drive. I had a similar problem once but I new it was the impeller because I had pieces of it in the water intake in the out drive. I replaced it and everything was alright. The alarm it self is hard to locate, but it seems to be near the fuel filter/pump area, and by the water flow schematics from the repair manual it looks like theres a bypass line that goes from the thremostate housing to the fuel pump area. I'm at a loss, except for the manifold sensors not sure what it might be, when I get home I'll look for those sensors again, but I am getting water coming out"
 
"I would take the thermostat h

"I would take the thermostat housing off the engine; remove the sensor, clean all the passages, re-install the thermostat, re-install the sensor and see what happens. The SLOW system (speed limiting operational warning) continually monitors oil pressure and water temperature. In the event of high temp (above 200F) the coolant temp switch will ground a low voltage signal in the ECM. The fact that your alarm is immediately going off would lead me to a faulty switch and as the engine builds temp it is kicking in the ECM."
 
"I basically already did this,

"I basically already did this, not sure if it was thorough enough, but when I checked the impeller I back flushed everything by pushing water up the intakes on the out drive and let it run through. I didn't get any debris, but maybe since the impeller is low in the motor I didn't get up into the motor area. I did make sure the housing for the thermostat was clear, and after re installing I disconnected the sensor but still got the alarm."
 
"Binary search debug time...

"Binary search debug time...
There are two catagories of possible problems:
1) Engine getting hot even though gauge says temp OK.
2) Engine not hot, but alarm system thinks it is.

Beg, borrow, steal or as a last resort spring for $40 bucks and buy a Infra Red temp gauge and see what temp the engine really is. That way we can tell if we are trying to find a catagory 1 or 2 problem.

I am not familiar with that particular model engine designation, so...silly question: FWC or raw? From the temps you are quoting, it would appear to be FWC... and if it is, is it a full or partial system?"
 
"It is 100% raw, no partial. I

"It is 100% raw, no partial. Impeller is on the front of the motor directly on to the crank shaft spindle with the intake coming in from the out drive. Intutition tells me it's not overheating but thinking it is. I am able to handle the hoses with my hand, I wanted to make sure there was circulation going through them so I squezzed them with the motor running and felt the flow going through them, not the infra red but... so the infra red is a laser type thing??, were do you get the reading from?

So let's assume that it's not truly overheating but thinks it is, I unplugged the temp sensor which is located on the thermastate housing and that didn't cure the alarm, I'm puzzled about that."
 
It probably isn't overheat

It probably isn't overheating if it is only warm to the touch. But removing the lead from the sensor will not shut the alarm down. Remember you have both senders for the gauges and separate sensors for the alarm system I believe the ECM/SLOW system is a closed circuit. The fact that the alarm is coming on as soon as the engine starts seems to point to a faulty sensor shorting to ground prematurely. On my 2000 GSi the OP sensor was bad. $18 cured that issue.
 
"OK this is where my automotiv

"OK this is where my automotive and Marine applications gets lost in translation, are you talking about the temp sensor on the thermostat housing that might be bad? You say the gauge has a sensor as well? Where would I find that one?"
 
"Some alarm systems are design

"Some alarm systems are designed so that if a sensor is disconnected an alarm happens.

Alarm system sensors and those sensors that drive the gauges are different. Typically, alarm system sensors are on/off type devices, while those sensors that drive the gauges are analog, i.e., they are devices with a resistance value that changes with the parameter, i.e., temp, pressure or fuel level.

The temp sensor in the T'stat housing drives the dash gauge."
 
"I have a new Cobalt 242 with

"I have a new Cobalt 242 with the Volvo Penta 5.7 GXI that has only 6 hours on it. I'm experiencing an audible alarm that goes off when the boat hits around 40 mph. A dealer mechanic has looked at this and does not know whether it's the cooling system or oil pressure valve. He disconnected the alarm and the ecm slowed the boat down and would not let it continue at that speed. Has anyone experienced this before? BTW, I have very little mechanical knowledge."
 
"George, there are two 'se

"George, there are two 'sensors/senders' for both the oil pressure and water temperature. The water temp sensor for the SLOW/alarm system is mounted in the thermostat housing and has a 2 lead wire harness plug. The sending unit for the water temp gauge is mounted in the intake manifold and has a single wire lead usually terminated in a ring connector that is secured to the sending unit by a nut. Replace the temp sensor. The temp gauge sending unit has no impact on the alarm system even if it is faulty.

Same story with the oil pressure. The SLOW/alarm sensor is located next to the oil filter and often clogs and triggers the alarm. The oil pressure gauge sending unit is located by the distributor and only provides the signal to the gauge and will not trigger the alarm even if the gauge stops working. In my experience the OP sensor causes more issues than the WT sensor. They are fairly inexpensive; I source from Doug Russell.com. I would replace both."
 
"Robert, check the thread on &

"Robert, check the thread on "5.7GSi won't rev above 2200 rpm". Your ECM is going into the SLOW mode but now you have to troubleshoot the root cause; water temperature, oil pressure, fuel/ignition or gearbox related?

Many forget to troubleshoot the outdrive. If the oil level is low that will trigger the alarm. Scary that the dealer doesn't have the proper tools to read the codes."
 
Thank you for the suggestions.

Thank you for the suggestions. This situation is quickly becoming frustrating as well as bewildering that the mechanic as well as the dealership owner has NEVER seen this before!! We traded in a Bryant deck boat that was only four years old that was consistently getting water in compartments that were suppose to be dry only to be sitting here scratching my head with now a new boat with a mystery problem.
 
"OK then, I have something to

"OK then, I have something to keep me busy. I will replace the sensors and first I shall check the oil level in the out drive"
 
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