POSTED July 27, 2022

Boat Transom Problems – Everything You lot Need To Know!

What happens to a fibreglass boat that has a wet or rotten transom, and why is it important to prepare information technology? We run through how a transom becomes wet, pictures of major telltale signs and cost to repair the transom correctly.

What is the transom?

A transom is the structural section of the back of the boat that the engines mount to. With an outboard, they mount to a bracket on the dorsum. With a sterndrive, they mount via a pigsty through the center and a transom assembly.

How does my transom get wet?

Water ingress to a transom can be caused past numerous reasons. All of these take a catamenia of time to develop, and getting h2o in your transom in one case will not necessarily rot information technology abroad overnight.

The nearly common failure points we've seen at BoatBuy are:

  • Damaged/croaky drain fittings to splash wells (outboards)
  • Perished sealant (silicone) to mounting bolts (outboards)
  • Transducer and trim tab mounting screws allowing water past
  • Leaking steering pin seals with unsealed transom shield mounting holes (sterndrive)
  • Through transom anode bolts(as these anodes are changed annually, without the utmost of care it'south quite probable to spin the bolts on removal and fitment of the anode – the spinning of the bolt breaks the sealant betwixt the bolt's washer and the transom)

It'south not merely the outer transom that needs to be sealed with any fixtures going into the transom, the inner transom and stringers should as well exist sealed as build up of bilge h2o can seep into any non-sealed fixtures.

  • wet transom with cracking
    Slap-up to a wet transom

How to make up one's mind if my transom is moisture?

Some telltale signs your transom has been affected past water ingress and needs attention could include:

  • Rust/brownish stains below screws or bolts
  • Visible pinch of the transom where mounting bolts secure an outboard
  • Visible compression or cracks noted to an inner transom around the sterndrive transom assembly
  • Gelcoat cracks around upper transom and splash well corners (suggests compromised integrity and flexing to the transom)
  • An audibly slow note and feeling a lack of rebound when performing a percussion examination of a transom
  • An audibly tinny (delamination) note when performing a percussion test of a transom
  • Elevated moisture readings in a particular area (water, salt, metals and ablative coatings can interfere with the accuracy of wet meter testing, results should be accomplished on a dry out transom and from the inside wherever possible)
  • Remove a screw an observe for corrosion and water entry to the transom

These are a series of indicators nosotros look out for at BoatBuy when completing a Pre-Purchase Inspection.

  • Engine mounting bolt showing croaky and compressed transom
  • Croaky transom
  • Exposed rotten transom coring
  • Elevated moisture readings side by side to exposed transom coring
  • Compressed transom bolt
    Compressed transom bolt
  • Rust stain below engine mountain bolt, indicating wet transom

Does it matter that there is h2o in the transom?

Yes, once water has entered a timber-cored transom it travels between these layers that create the integrity of your transom. If yous tin imagine, with every gear change and with the boat thrusting frontwards and aft every time you accelerate and decelerate, the h2o between these layers has a hydraulic effect, pulsing and pushing h2o with extreme pressures further throughout the transom. This is known as water migration and hydraulic erosion. The migration of this water causes timber core shredding, further areas of delamination and eventually an irreversible complete core failure and the entire transom must be replaced.

How to repair a wet transom?

The decision on whether a transom can be repaired should be decided by a shipwright or boat architect willing to consummate and warrant the work. This could include core samples to be extracted and examined, to various areas of the transom to determine the extent of wet spread. Sterndrive or anode mounting holes could be over bored to eliminate areas of moisture, corefilled and re-glassed, these spot repairs should exist noted to be a repair of temporary nature, as the integrity of the residual of the transom is unknown. Ultimately, the most complete and thorough repair to a transom is a transom replacement. Chris Austin from FibreFinish has a good article near it here.

How much does it cost to replace a transom?

On a modest outboard driven boat with easy admission, you may exist looking around $4000-$6000. It's important to think that any major transom work is going to require the motor removed, and the hull taken back to bare to permit admission to cutting the entire timber core department out (without damaging the outer skin).

On a larger gunkhole, you could be looking anywhere from $5000-$15,000. It'south non uncommon to find the water has tracked further into the stringer system (if timber cored also), compromising the hull further and adding additional costs.

What percentage of moisture is also high for a moisture timber cored transom?

Provided in that location are no other factors affecting the readings for example anti-foul coatings, metal, residue salt:

v-20% – Considered normal

20-30% – Transom has deteriorated and is letting h2o in

30% + – Basically underwater!

Percussion testing should be used in conjunction with a wet meter to go the near accurate results. Timber has a natural moisture content of between five and 15% then these levels are considered normal. When an elevated reading is returned the side by side step is invasive testing such as core sampling, which involves drilling a number of holes into the transom and assessing the shavings produced from the drill bit to see how far the rot has travelled.

Professional person inspections

The older the boat, the more probable a moisture transom will exist uncovered. Information technology takes a mix of a trained center, special tools and experience to uncover a transom consequence, and our entire team are trained to detect these issues.

Having one of the BoatBuy team assess your boat not only covers the hull, but a number of other of import areas including a ocean trial to ensure you're making an informed buy. We provide our comprehensive services in both Queensland and New South Wales. Feel complimentary to get in contact or book in a Pre-Purchase Boat Inspection today.