Volvo Penta MD7A Engine Questions

[Ross20550]

I have a Sabre 28 sailboat with a Volvo Penta MD7A Engine. Over the years the engine has been very dependable although a number of parts have been changed. I need help regarding two questions. And I'm not really handy with engine parts work.
1. I've noticed recently that my temperature gauge is remaining in the cold setting, just a bit above the 100 mark. The oil pressure had been excellent and everything seems to be ok but I'm concerned about this temperature and don't know how to chedk to find out if there is a problem, is the gauge is at fault or something else. Also how muchof a problem this may be.
2. For a number of years my amps meter has not functioned. I have the same question regarding how to check to find the source of the problem. I'll attach a photo of the cockpit gauges.

 

[Mark Maulden]

Get a laser thermometer and measure different parts of the engine to see what it's really running at. If it is really running cold, take the thermostat out and put in pan of water on the stove with a thermometer and see if it works. Or you might be able to tell if it stuck open visually.
As for the ammeter, i think you have to decide if you really want that meter or if a simple voltmeter would suffice. If you want it, the first thing is to replace it as it looks to have a severely bent needle. Then need to figure out wiring.

 

[Stu Jackson]

As for the ammeter, i think you have to decide if you really want that meter or if a simple voltmeter would suffice. If you want it, the first thing is to replace it as it looks to have a severely bent needle. Then need to figure out wiring.

Mark's right. The downside to an ammeter in the cockpit is the long wire run for charging your batteries, since all the charge power from your alternator (and, perhaps, your shorepower charger, depending on how it's wired) has to run through the ammeter.

Many years ago, Catalina switched from ammeters to voltmeters in their cockpit panels.

Here's why:

• Engine harness upgrade: A comprehensive overview by Gerry Douglas Important WARNING for M25 owners

The article discusses three basic things: the poor trailer connections, the wiring itself (which is usually pretty good - ours still works and the boat is 30 years old) and the ammeter.

Don't know what you know or don't, this might explain also:

Ammeters & Shunts 101: http://c34.org/bbs/index.php/topic,6032.0.html
http://c34.org/bbs/index.php/topic,6032.0.html
If you want good charging of your house bank from your engine, get rid of the ammeter.

Good luck.

 

[Capt jgw]

On the temp gauge, does the needle move at all or stays stuck in one spot? If it doesn't move at all probably the gauge itself is bad. Try jumping the"Sender" terminal to ground. The gauge should peg to high. (Or is it low, doesn't matter, it will move if the gauge works.)
On the ammeter, I agree with the others, it's best to swap it for a volt meter. You can still see if you're charging by seeing the voltage rise, and the gauge only needs power and ground to work. The link above for the Universal wiring upgrade is just as valid on the Volvo. If there are any disconnected on the harness they're probably not as crappy as the Universal ones, but are still a failure point. They're only there to make installing the engine easier, once it's in you don't need them anymore. The plugs can be cut out and replaced with good heat shrink butt crimps. Much more reliable.