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The Case of the Increasing List

How important is a slight list on a small boat?The client called me after the dealership he purchased the (New) boat from four years earlier and his local mechanic could not determine the cause of a starboard list that seemed to be increasing each year.

He mentioned that the list was almost imperceptible after the second year, but was very noticeable after this, the fourth year of his ownership. He actually picked up on the problem while he was painting the bottom the second year and noticed the scum line at the transom on the starboard side was just about an inch above the water line.

He let it go for a while because he thought the full tanks or other gear stored on one side may have been the cause. He also thought there was a possibility that the factory may have improperly installed the water line. So, he painted up to the scum line the third year and all seemed well.

The season passed by and his boat was hauled and prepared for winter storage by the yard. When he arrived to remove his personal gear for the winter he noticed that the scum line had gained a further foothold on the starboard side, aft.

The starboard side scum line was about an inch higher than the previous year. About another inch had been added to the starboard side while the scum line on the port side also increased about a half inch. Now he knew he had a problem because about halfway through the season he managed to keep the fuel, water, and waste tanks close to empty and only added fuel or water when he was going out for the weekend. He also kept track of all extraneous gear aboard and kept it to a minimum.

Initial Investigation

For a 24-foot boat, common balance issues such as uneven tanks or an inoperative bilge pump were initially considered. However, the story’s progression suggested something more unusual. The boat’s construction included a transom with a plywood core and a solid fiberglass laminate bottom. After a thorough inspection and percussion testing, a less crisp sound on the starboard side indicated potential moisture retention.

Moisture and Core Sampling

Moisture testing utilized advanced capacitance moisture meters to detect water intrusion in the laminate layers. These meters provided precise readings of moisture levels within the boat’s fiberglass structure. Additionally, core sampling involved drilling small holes into the affected areas to extract material samples for closer examination. This revealed critical details such as the extent of delamination and resin inadequacies, offering a clearer picture of the structural compromise. These methods ensured a thorough understanding of the damage, guiding effective repair strategies.

Moisture meter readings and core samples revealed significant water saturation in the starboard side’s laminate and transom. Core samples exposed delaminated areas and inadequate resin application during factory lamination. This improper sealing allowed water infiltration, leading to structural imbalance.

Fuel Tanks: Unexpected Challenges

Fuel tanks vary in material and design, ranging from aluminum to fiberglass. Water, bacteria, and debris often infiltrate tanks, causing operational issues. Fuel pickup tubes, typically designed to avoid bottom debris, can suffer corrosion or blockages. For example:

  • Corroded Pickup Tube: In one case, a disconnected fuel gauge hid the fact that a tank pickup tube had corroded at its connection, rendering a full tank unusable.
  • Bacterial Colonies: On another vessel, gelatinous bacterial blobs blocked the pickup tube, causing intermittent engine idling during choppy conditions. Cleaning revealed the hidden colonies.
  • Hot Item Incident: A significant issue arose when a heat-generating device stored near the fuel tank caused a partial melt of the insulation, leading to fuel odors and potential safety hazards. Relocating the item resolved the issue but highlighted the risks of improper stowage.

Hot exhaust risers can indicate a serious problem

While the engine exhaust riser temperature can vary between manufacturers and old versus new risers, the temperature should not exceed a temperature that is warm to the touch. If you can not hold your hand on the riser, it is too hot. In the absence of a portable thermometer, the surveyor should be able to touch the riser without pain or injury. Even if the engine temperature gauge indicates a normal temperature, the riser may be in poor condition.

Hot exhaust risers
Hot exhaust risers

If the risers cooling water passages are constricted, note photo below, sufficient water will not pass through to properly cool the remainder of the exhaust system. In many systems the next link is rubber which will burn when sufficient cooling water is restricted. Once the rubber portion burns two things are likely to occur.

Boat Engine
Boat Engine
  1. Seawater will enter the hull.
  2. An engine compartment fire will ensue.

The riser pictured below has been in use in salt water, summer’s only, for four seasons. Viewing the riser from the top (Figure 1), which is often the only view available, indicates a riser that is in good condition and free from rust. Notice the view from the bottom photo, which indicates the cooling water passages are almost completely blocked.

Riser
Riser

The Elbow Caused the Fire

Another notable case involved a fuel line elbow connector that failed due to substandard material. This failure led to a fuel leak, igniting a fire in the engine compartment. Fortunately, quick action with a fire extinguisher contained the damage. The investigation revealed that using certified, high-quality components could have prevented this incident.

The photos below are of the elbow, which when new was an integral part of the ring in the photos above. The red arrows indicate areas of complete oxidation. The red arrow in the center photo indicates complete loss of the inner liner of the water jacket. The photo, below right, shows an area that was covered by the rubber exhaust hose. This area is also completely oxidized and could not be inspected because the exhaust hose covered it. The photo (below) shows the two components that were joined by the stainless clamp and rusted iron in the first photos as they might have been seen before the fire. The red arrow indicates the placement of the stainless clamp that hid the rusted cast iron joint that broke free. The material pictured (bottom right) is rusted iron scale. It is the remnants of the water jacket of the elbow.

Importance of Sea Trials

Sea trials are essential for testing fuel systems and identifying hidden issues. During one trial, a disconnected wire at a fuel gauge revealed an owner’s attempt to mask tank problems. Another trial exposed bacterial blockages in rough seas, underscoring the need for real-world testing conditions.

Fuel tanks vary in material and design, ranging from aluminum to fiberglass. Water, bacteria, and debris often infiltrate tanks, causing operational issues. Fuel pickup tubes, typically designed to avoid bottom debris, can suffer corrosion or blockages. For example:

  • Corroded Pickup Tube: In one case, a disconnected fuel gauge hid the fact that a tank pickup tube had corroded at its connection, rendering a full tank unusable.
  • Bacterial Colonies: On another vessel, gelatinous bacterial blobs blocked the pickup tube, causing intermittent engine idling during choppy conditions. Cleaning revealed the hidden colonies.

Stern Drives: Hidden Corrosion

Stern drives often hide significant issues. While exterior casings may look fine, internal corrosion can compromise performance. Key points include:

  • Electrolysis Damage: Ground wires and zinc anodes must be maintained to prevent internal corrosion.
  • Cosmetic Repairs: In one case, a “rebuilt” stern drive was merely cosmetically repaired, hiding severe corrosion with epoxy filler.
  • Bellows Maintenance: Neglected bellows can lead to leaks, resulting in potential sinking or catastrophic failure.

Conclusion

Small issues on boats, like slight lists, can signify deeper structural problems. Thorough inspections, moisture testing, sea trials, and an understanding of boat systems are vital to ensuring safety and performance. Whether it’s a hidden moisture issue, fuel system failure, or stern drive corrosion, addressing these challenges early prevents costly repairs and ensures smooth sailing.

For expert marine inspections, trust Classic Yacht Marine Surveyors, serving all of Texas and the Gulf Coast region. Our team specializes in uncovering hidden issues, ensuring your vessel’s safety and performance.

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