Volvo MD11C - Mysterious Overheat Issue

[SailMaster]

ThIs engine starts up beautifully and runs like a sewing machine. However she heats up after about 15 minutes. There is, what appears to be, sufficient water flow through the exhaust. However, she heats up into the red after 15 ,minutes. I had tbought the sea strainer was plugged. Tried to service that and could not get the wing nuts off. Corroded on solid. I bypassed the sea strainer with a longer cooling hose from the raw water inlet to the engine. Still overheats. We then had a diver check the raw water inlet from the outside and found some contamination. That was cleaned and it improved the water flow a bit. But we are still over heating.

Does anyone have any thoughts on what else to check.

This boat ran fine for4 hours and then sat for 5 months. The previous owner did not bother to ever clean the bottom. I have had it done on a regular basis.

 

[JamesG161]

Go to this link for diagrams on your sea water cooling system.

Cooling System - 7742230 - volvopentastore.com

Jim...

 

[JamesG161]

When you pick which system is same as yours, I can help you, if you point out your cooling system

I have MD22L engine.

Jim...

 

[SailMaster]

I’m not sure which one this is. It is raw water cooled.though.

 

[JamesG161]

I’m not sure which one this is. It is raw water cooled.though.

Serial number on the engine plate will key you the right version.

Jim...

 

[Ralph Johnstone]

Does anyone have any thoughts on what else to check.

The heat exchanger may hold a few nasty surprises.

 

[JamesG161]

This is the most likely set up for your MD11C

To find the issue, you need to trace the water flow from part #54 to the exit of the boat thru Part #57.

Your water pump = #26

Part #1 = Engine hot AntiFreeze to cooling water heat exchanger.
_____

I picked [guessing] the part ID 825916 for water pump #26 and did a web search and found this.

The heat exchanger may hold a few nasty surprises.

His best guess and mine too.

The Black Star Item is the water pump impeller. If not changed often, it breaks up and restricts the Inlet to the heat exchanger.

You might need a Laser Temperature device, hand held, to trace the heat flow from IN to OUT of boat, while idling your engine.

Then people on SBO will help you more. Pictures of your engine help too.

Good Luck..

Jim...

 

[SailMaster]

Good morning,
I believe we have restricted flow at the through hull due to a failure in the valve movement. Our diver cleared a barnacle, however there is no change in water flow when I move the valve from open to close and vise versa. I have scheduled a haul out to replace it.

Thanks guys. Wish me luck.
W

 

[Ralph Johnstone]

A thought for when you are hauled, see if you can alter your piping to fit this arrangement :

Very briefly : to clear your inlet, unscrew the plug, attach a clear vinyl hose and stand vertically, open the valve and rod with a 1/4" wooden dowel.