brico
Well-known member
- Joined
- Dec 25, 2013
- Messages
- 311
- Status
- OWNER - I own a Hatteras Yacht
- Hatteras Model
- 37' CONVERTIBLE (1977 - 1982)
Today i got my marine engineer buddy to come over to see my (new to me boat) and I told him how ever since I got it, the Starboard engine has the steam slowly coming out at over 1500 RM and at WOT very little water comes out of the exhaust and a lot of steam is generated. I only run the engine at WOT for few minutes anyway. At the pre purchase inspection the raw water pump impeller was inspected and found in good condition with all blades intact.
Well, my buddy said, let's open up that oil cooler/heat exchanger that is on the raw water line going into the main Heat Exchanger. What do we find. A lot of impeller rubber blades stuck in there obviously restricting the water flow. When we removed it we also found few tubes clogged with scale and decomposed zinc anodes residue, but the main culprit was obviously the amount of rubber from impeller blades.
The Port engine oil cooler only had two broken off old zinc anodes stuck in there, but nowhere near the flow restriction as the rubber impeller blades on the Starboard side.
What we have concluded is that who ever replaced the broken impellers in the past should have known that missing blades could not have worked themselves out of the system but are stuck at the entrance to the oil cooler with tiny 2-3 mm tubes through which only thing that can flow is water, some mud and smaller bits/dust of decomposing zinc anodes. Any rubber bits from the raw water pump impeller would have got stuck there in the oil cooler and in turn reduced the the water flow to the main H/E.
I have taken both of the coolers home to try and chemically clean them. DD Manual calls for 1part Muriatic Acid 2 parts water and 1/2 pound of Oxalic acid for each 2.5 gallons of solution. Soak the H/E in until the bubbling stops, this usually lasts 30 seconds to a minute and then rinse with warm water.
How well does this solution actually clean the scale and hardened zinc anode bits in the tubes? Would diluted Muriatic Acid alone work without the need to add Oxalic Acid? Does 30 seconds to a minute in this solution really softens up and removes the scale? Any advice regarding effective chemical cleaning of the H/Es is much appreciated.
Well, my buddy said, let's open up that oil cooler/heat exchanger that is on the raw water line going into the main Heat Exchanger. What do we find. A lot of impeller rubber blades stuck in there obviously restricting the water flow. When we removed it we also found few tubes clogged with scale and decomposed zinc anodes residue, but the main culprit was obviously the amount of rubber from impeller blades.
The Port engine oil cooler only had two broken off old zinc anodes stuck in there, but nowhere near the flow restriction as the rubber impeller blades on the Starboard side.
What we have concluded is that who ever replaced the broken impellers in the past should have known that missing blades could not have worked themselves out of the system but are stuck at the entrance to the oil cooler with tiny 2-3 mm tubes through which only thing that can flow is water, some mud and smaller bits/dust of decomposing zinc anodes. Any rubber bits from the raw water pump impeller would have got stuck there in the oil cooler and in turn reduced the the water flow to the main H/E.
I have taken both of the coolers home to try and chemically clean them. DD Manual calls for 1part Muriatic Acid 2 parts water and 1/2 pound of Oxalic acid for each 2.5 gallons of solution. Soak the H/E in until the bubbling stops, this usually lasts 30 seconds to a minute and then rinse with warm water.
How well does this solution actually clean the scale and hardened zinc anode bits in the tubes? Would diluted Muriatic Acid alone work without the need to add Oxalic Acid? Does 30 seconds to a minute in this solution really softens up and removes the scale? Any advice regarding effective chemical cleaning of the H/Es is much appreciated.
