How To

How to Repair a Damaged Base Fin of an Outboard Motor?

The fin is a fin-shaped piece that acts as a rudder and controls the direction of the boat. It also protects the propeller and gear case that incorporates some elements of the transmission system. Generally used on small boats, the wing of an outboard motor can be severely damaged, especially when navigating in shallow rocky areas. You can also read our cheap outboard motor buying guide to choose the perfect outboard motor.

The costs of repairing a damaged base vary according to the severity of the impact (breakage, cracks, deformation, etc.). It is generally costly to involve a specialist. You’ll see that everyone can do it and I’ll show it to you in this article. You will learn how to repair a damaged base fin quickly and efficiently on your outboard motor. There are several solutions that we will review.

Solder the base of an outboard motor

The base fin is an essential piece that contributes to the directional stability of the boat. Whether it is caused by a fall or a shock against rocks, the damage of the fin damages the security of the boat.

It also makes it difficult to control the steering and generates vibrations. In the event of a broken rear fin, the propeller and the transmission components of the outboard boat may be damaged at the slightest impact.

Welding the damaged part of the base is a practical solution to restore the outboard motor base quickly. However, this operation requires knowledge of welding, including the mastery of the arc welding process.

Moreover, this process is only suitable if the part has broken and has not been lost; in this case, it should be used.

How to weld the flange fin?

First, clean the base with a degreaser. The standards must sand the part to be welded in force for the welding of aluminum.

It must also proceed by making a V-groove of about 45 ° on both sides of the parts to be welded. The operation must be carried out using an electrode adapted to the materials making up the base of the motor. After welding, the welded parts should be painted with anti-corrosion and antifouling paint.

Mount a “SkegShield” base protection kit

The “SkegShield ” base protection kit is generally made from heavy-duty stainless steel alloys. It therefore effectively protects the lower part of the base of your engine against rocks and floating debris.

You can also use it to repair a broken or deformed base fin. Mounting a protection kit is a smooth operation that does not require specific knowledge and can be done without welding.

Moreover, the protective fin is custom-made to suit different types of outboard motors. Compared to welding, this is a quicker and easier solution to repair a broken base fin.

Competence level


Duration of the operation

2 hours on average

Parts and tools needed

  • Skegshield base protection kit (protective fin + mounting kit)
  • A jigsaw
  • A drill
  • A cobalt drill or HSS 1/4
  • A wire brush
  • A Scotch-Brite (preferably 3M)
  • A plastic or wooden hammer
  • A file or abrasive paper
  • A cloth
  • Acetone


  • Using a jigsaw, cut out the damaged portion of the fin from the base. The remaining part of the fin must be at least 50 mm, otherwise the “SkegShield” kit can not be mounted correctly on the base.
  • It is convenient to remove the outboard motor transmission case before starting the repair.
  • This is not a necessary condition, but it dramatically facilitates the cutting, screwing and assembly of the kit. This is also an opportunity to check the transmission system as well as the water pump. In general, it is an effortless operation on most outboard engines available on the market.
  • After cutting the damaged part of the base, prepare the remaining surface of the fin with a file or sandpaper. Sharpen the cut edges using a wire brush and Scotch Brite and wipe with a cloth soaked in solvent.
  • Then how to mount a transducer on an aluminum boat the protective fin on the base. With a plastic or wood hammer, tap on the attached flap and make sure it is snug.
  • With a drill, drill two holes in the remaining area of ​​the damaged fin so that they match those pre-drilled on the protective fin. Then screw the protective propeller to the base using the screws and locking elements supplied with the mounting kit.
  • Your engine is now ready!

Repairing an outboard engine base fin: what to remember

A damaged base fin can cause severe problems to the propeller and transmission components and your outboard motor. It is, therefore, imperative to repair it as soon as possible. Although it is possible to weld a broken or cracked fin, the simplest solution is to mount a base protection kit. Remember to choose a well-known brand to avoid unpleasant surprises 

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