Engine Overheating - Bavaria 30 Cruiser (2005)

[Bronco 30]

Hi,

After being repaired (twice) my engine still overheats.

After a few hours (4) at low speed (near 1500 rpm) the engine alarm buzz. (Cold water on external refrigeration circuit)
Another symptom is that I have Steam on tap, instead of hot water ...
I stopped the engine, and emptied the hot water, waited for a couple of hours, started again at less then 800 rpm and kept replacing the water in the boiler, every half hour with cold water from tank. (Just opening the tap)
After 14 miles (14 hours) I ran out of fresh water, and kept the tap opened. The engine was cold.
Upon finally entering the marina had a new alarm (beep - didn't looked at the status lights on the board) that stopped while in neutral ...

Maybe someone can give me a clue. I think this (Buzzes and overheating) is somehow related to somekind of a thermostat . (Engine? boiler?)
About the second issue -beeps while not in neutral - I have no clue. (Running out of fresh water  on tank ?? Motor collapsed?)

I would appreciate an opinion in order to have a clear identification of these issues to get it (finally) repaired.

Thank you

Regards,
J. Meirim

[Trapeze Artist]

I'm a little confused by your description, Bronco. Not sure if the reference to the calorifier and domestic hot water is a red herring or not. My boat produces sizzling hot water, although I've been told there is a thermostat somewhere, which I can't find.

Putting the domestic water system to one side, the first question is whether your raw water circuit is in order. Do you have a reasonable flow of water coming out of the exhaust? Is it warm but not hot when you put your hand in the stream? If the flow is very poor or non-existent, the first place to look is the impeller. If the impeller has lost a blade it won't be pumping very efficiently and the missing blade may be partially blocking the heat exchanger.

If the impeller is good, or if you have to go hunting the broken bits, the next stage is to take off the elbow at the front end of the heat exchanger. Poke something (wire coathanger, maybe) down each of the tubes to make sure they are clear. If they're not, you'll probably have to dismantle the whole heat exchanger to clean it up.

If you haven't found a problem yet, inspect the exhaust all the way back from the elbow to the outlet on the hull. I can't imagine what problem might occur there, but it's best to check.

If the raw water passes all the tests, check the coolant circuit. I've never touched this bit, but the obvious things would seem to be
Is there enough coolant?
Is the thermostat working properly?
Is the pump doing what a pump should do?

[Bronco 30]

Thank you for your reply
Raw water circuit in order+ impeller. (revised 2 times). The water is warm not by hand contact. Flow is normal.
Exhaust circuit (re)checked and OK

Coolant level OK. No leaks, oil, water of any kind.

Must check Thermostat and pump.

Thank you
J. Meirim

[Marchi]

Are you talking about thermostat on motor cooling circuit or some thermostat on boiler hot water cicuit?
I'm having same problem with steming water on tap.

[Marchi]

Found thermostat on hot water outlet. Maybe this is the reason!?

http://www.marinepartseurope.com/en/volvo-penta-quick-find.aspx?Catalog=7740690&Category=90&View=9293

[Trapeze Artist]

I think Bronco's engine will be a D1-20 (unless some early 2005s had a MD2020). In which case the thermostat appears to be on the back of the heat exchanger.
http://www.marinepartseurope.com/en/volvo-penta-quick-find.aspx?Catalog=7746500&Category=26&View=9709

[Bronco 30]

Are you talking about thermostat on motor cooling circuit or some thermostat on boiler hot water circuit?
I'm having same problem with steaming water on tap.

Not really sure. I think that the main problem is that the engine is heating water in the boiler, but somehow doesn't get info to stop.
This result in boiler heating the engine...
I realise now that I get steam on tap in 2 ways. Electrical connected (in marina) or by engine after buzz from the engine.

If there are 2 thermostats (?), I bet on the boiler.

Thank you
J. Meirim