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OldManMirage 19-02-2018 03:59

How to add engine alarms
Ok, my Volvo Penta MD7A does not have alarms for low oil pressure or high temperature. This is how many of them come apparently.

How can I add them ? I've looked around some and I don't see anything that seems to be what I want. Do they make a kit to do this ?

Thanks for any help !

moctrams 19-02-2018 04:48

Re: How to add engine alarms
This should help.

I've seen engine with a "T" pipe screwed in and all you have to do is a add a low oil pressure and oil pressure sensor. Run the wires to your new gauges.

ranger42c 19-02-2018 06:14

Re: How to add engine alarms
If you already have oil pressure and water (coolant) temperature gauges... CruzPro's digital gauges (for example) have an alarm function you can set.


jamhass 19-02-2018 07:30

Re: How to add engine alarms
You can switch your sensors to the combo types (with the alarm switch built in) then add idiot lights and sonic alarm. You can use 2 alarms (easiest) or just 1 with diodes to separate the functions (not hard but extra work.) Alternately, you can just use 1 idiot light and alarm paralleled to the 2 switches and then look at the gauges to see which is unhappy.

Bill O 19-02-2018 08:19

Re: How to add engine alarms
Looks like you are doing many nice upgrades on your boat.

We are using a type of thermal sensor on our refrigeration unit to turn the unit off if it gets too hot. It's very simple, reliable and will reset when it comes back down to its prescribed temp. Our opens to cut off power to the unit, but you can find a similar one that closes (at the temp you choose) which then connects to audible alarm (something annoying and can be heard over the motor). May want an off switch to turn the audible alarm off, but then it's not as fool proof (if you forget to turn it back on).

The suggestion for the T pipe fitting should cover the oil pressure alarm.

Bill O.

Alita49DS 19-02-2018 09:35

Re: How to add engine alarms
As far as temperature is concerned, I was told that by the time any engine gauge/alarm showed it was probably too late. That the thing to do was to fit an exhaust temperature monitor.

I bought a NASA one and fitted it. Not hard. It has both an LCD readout and an alarm.

You might want to read up about the subject and consider that option.

S/V Alchemy 19-02-2018 09:46

Re: How to add engine alarms

Originally Posted by Alita49DS (Post 2580751)
As far as temperature is concerned, I was told that by the time any engine gauge/alarm showed it was probably too late. That the thing to do was to fit an exhaust temperature monitor.

I bought a NASA one and fitted it. Not hard. It has both an LCD readout and an alarm.

You might want to read up about the subject and consider that option.

Yep, also known as "exhaust gas temperature" (EGT) monitor or "pyrometer". Trucks use them, too. Other good alarms to have are related, like one that tells you if the water circuit is failed or failing, which relies on a flow measurement.

DougR 19-02-2018 09:48

Re: How to add engine alarms
Originally the MD7a engine was supplied with high water temp and low oil pressure alarm switches mounted on the engine and they drove an alarm system on the instrument panel which consisted of two idiot lights and a buzzer.

The temp switch was mounted in the forward outboard side of the exhaust manifold and the oil pressure switch was on the side of the engine block a little ways above the oil filter location.

Check to see if you have alarm senders/ switches mounted in these locations, and if so, check to see if they are functioning. The oil switch should close to ground at about 7 or 8 psi and the temp switch closes to ground probably somewhere around 180 or 190F, but I'm not sure about that temp. off the top of my head. You can check it by looking in the service manual linked in this thread.

If you have senders but the alarms don't work, try removing the wire from the sender when the engine is running and grounding the wire to the body of the sender. This simulates an alarm situation and should cause an alarm to sound and a light to illuminate.

If no switches are mounted, then you need to think about sourcing an alarm kit, and these are easy to find on line.


mikecambrai 19-02-2018 10:04

Re: How to add engine alarms
The 2 most important temperature sensors that I always fit are:
1. On the exhaust outlet where the water leaves the engine and goes into the exhaust pipe. Looking for lack of water flow.
2. I clip or add with epoxy, a sensor on the Jabsco body. Most problems with engines occur because of that silly little impeller failure or some other rubber bit like a hose or a belt.
Oil pressure is usually covered by the alarms on the engine panel.

OldManMirage 19-02-2018 11:58

Re: How to add engine alarms
Thanks y'all, lots of good info. Yes, I am definitely trying to upgrade a LOT of stuff on my lovely lady.

I probably should have added I have a temperature gauge, just no alarm. I like buzzers letting me know stuff is going wrong in case I miss it.

The T idea for oil is good. I do have a huge Volvo manual for my engine with breakdowns of everything. Its like a phonebook ! (remember those ? that means you are OLD !! LOL ) So I will look more closely at the engine.

And actually, I just had a new/old engine delivered to me yesterday. So I can look at the whole engine sitting on a pallet right here at my house and figure everything out. I'll be taking my old engine out after the summer, cleaning up the engine area, and installing the new/old engine. I say new/old because it's a rebuilt.

I've got room around the engine panel in the cockpit (protected). Just need some good buzzers and how to wire them in.

And FWIW, the new/old engine got bearings, rings, injectors and fuel pump rebuilt. I plan on doing the water pump. Anything else you can think of ? I also have a spare alt and starter I'll have reconditioned, and when I pull my old engine I'll strip off anything useful there. Alt, starter, injectors, fuel pump, water pump. What else ?

Roniszoro 19-02-2018 12:04

Re: How to add engine alarms
May I suggest alarms in both the cockpit area and down below as well.

A friend cooked an engine when charging the batteries when he was below listing to the stereo and didn't hear the alarm sounding in the cockpit. It cost practically nothing to have the additional alarm but is well worth it. This falls into the "an ounce of prevention is worth a pound of cure" category.

basssears 19-02-2018 13:16

Re: How to add engine alarms
I am definitely still a believer in my standard temp gauges (I installed a second so we have one in cockpit and in pilothouse) but they're just used for making sure everything's warming up right etc.

But for alarms, I agree, you don't want to count on anything related to the coolant because it can be gone (and therefore not register) or even if coolant is there by the time it gets hot it's too late.

I used alarm system from Engine Watchdog (ENGINE WATCHDOG Audible Engine Overheating Alarm, Gauge & Sensor) to add two temperature alarms, both based simply on the temperature the ring terminal at the end of the sensor wire reads (so no worrying about whether there's still coolant in there or not, it just reads temp... period). We ran one ring terminal to a convenient bolt on the block and used a large hose clamp to attach the other to the exhaust elbow, just before it goes to rubber. The temperatures are arbitrary, you just run the engine like normal while watching your regular temp gauge and figure that's your usual temp for that location, and set the alarm a few degrees higher. It has two wires out for wiring in a louder alarm if you choose.

Here's details of the install we did:
Some like it hot… (and other mods) – Sailing Idaho, the Salish Sea and beyond
... after we lost our fresh water pump and didn't know it and only through blind luck did we not cook our engine.

I believe there are other manufacturers of these types of temp alarms, but this was what I was pointed at at the time we did the project.

We've been very happy with the setup, to the point we added a third single unit to monitor transmission temps:
Spring Work – All About the Power – Sailing Idaho, the Salish Sea and beyond

-- Bass

Capella 19-02-2018 21:23

Re: How to add engine alarms

If you have an N2K network, you can install an Actisense EMU-1, which allows you to monitor several sensors and alarms.


Simi 60 19-02-2018 22:13

Re: How to add engine alarms
Aside from visual gauges I run this
Very loud audible, dial in the temps yourself.
I have one sensor on the oil filter and one on the raw water out before it goes into the exhaust.
Both held on with electrical ties.
Australian made $130

Dougtiff 20-02-2018 00:10

Re: How to add engine alarms
Google "aqualarm", great system, they have every type of sensor needed for your engine, the warning bell will wake the dead.

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