Repowering a sailboat

Author: Monica Lorenzo

To change the engine of a boat

The engine of the sailboat  is a main piece for the maneuvers of our boat.

Whether due to lack of maintenance or just wear, a time may come when it is safer and more cost effective to change the engine of the boat, repower, than to repair the old one.
As long as we can not guarantee that the engine of the boat is going to effectively respond, is time to change.

Josep Font and Jordi Vizcarra, from Nautica el Port de l’Escala, share with us in this video the step by step of how to repower a sailboat, what to consider when choosing a new marine engine, during the installation and basic maintenance.

Other reasons to repower the boat might be to increase the power, reduce weight, to have a higher control of the ship during maneuvers or just to increase safety.

Basic marine engine maintenance

Especially before a long sail trip and at least once a year (depending on the operation hours) there are some actions we must do for the basic maintenance of the engine of the boat:

  • We will check the oil level and the texture, confirming it has enough quantity and it is fluid and clean. Both in the engine and the gearbox.
  • We will do the same with the coolant. And we must also always have spare liquids aboard to react if there is a leak.
  • We will check the rubber stuffing box.
  • Hoses and rubber, we will see that they do not leak and are in good shape.
  • Filter change. We will change the filters of the gasoil, oil and air, following manufacturer instructions.
  • Impeller and water coolant circuit. We will check and confirm that they are properly functioning and that the engine gets properly cooled.

Before repowering

The first to consider when choosing a new marine engine is the measurements and the position of the hoses and circuits.

We must choose an engine that fits and adapts to the space that we have on the bench (height, width) and cabin and that it allows an easy installation and easy access for future maintenance (filter change, oil change…)

We will also check the surroundings of the engine (hoses, shaft…) and the ones that are not correct, must be replaced, also those required by the new engine such as the propeller. We always must do the new propeller analysis.

It is wise to choose manufacturers that guarantee spare parts and accessories in our main sailing areas, as well as a fast and high-quality after-sales service.

It is recommended to choose marine engines with little electronics since it has an easier maintenance.

Engine aligning

Aligning the marine engine means to adjust the position of the engine to the shaft of the boat.

Nowadays many marine engine manufacturers offer us the possibility to buy bench adaptation kit. That means that if we provide them the measurements of the bench and the old engine, as well as the position of the installation, they will provide us an easy to install kit on the old bench. This is a saving of an 80% of the installation cost, besides materials.

Once we have set the new engine on the bench, we must align it, that means that it matches the coupling position perfectly.

We can not move the shaft, since it is fixed on the installation through the boat’s hull, so we move the engine up and down with the silent blocks. An improper alignment might generate bad consequences for the boat, such as vibrations and water leaking. If we choose a flexible coupling this alignment might be a little easier.

Related marine accessories

This is the perfect time to review all the marine engine related accessories and think about a replacement: Propeller, shaft, packing, water and gasoil circuits and exhaust pipe, electrical installation…


To be able to mimic the electrical installation it is a good idea to take a picture or do a map with the old electrical installation, with the relationship of the cables and connections.
Once the engine is set, we will connect the alternator (positive and negative).


Next step will be to couple the external circuits: Exhaust, water and gasoil.

It is recommended to install a water separator and fuel filter that we connect the gasoil inlet to remove moisture and particles from the diesel to protect the engine fuel system

Gear shift

We will connect the gear shift cable. The cable is set on a special bridge that sustains it and the terminal goes to the transmission and is adjusted with the screw. Once installed we will go to the deck to make sure it goes front and backward.

Control panel

It is very easy to change the control panel, you just must ask for the right length of the cables when you order the engine.

First, you remove the four screws of the frame on the deck of the boat and remove the old cables. Then install the new control panel with the new connections and send the cable line to the engine.


We will load the engine with the needed liquids: Oil, coolant and if needed, ATF oil.

To know how much oil, we must follow manufacturer instructions, and it is very important to consider the angle of installation of the engine, since we can misunderstand the reading of the oil indicator and we might need more that the dipstick indicator says.

After checking the liquids, we star the engine for a few minutes, we turn it off, we wait for it to cool down and for all the oil to settle in the sump and we check the level again. Since probably we will need to add more due to the absorption of the filters and the circuit.

After 30 running hour of the engine it is time for the engine overhaul (oil changes and filters) since a new engine creates waste microparticles that go to the liquids and filters and might obstruct the circulation.

Starting the engine

We will open the sea water cocks, we will start the engine and we will look at the exhaust, the vVibration of the engine, the sound it does, stability, power, gears, tachometer turns, temperature alarms and the correct operation of all other elements.


A repowering of a boat or an installation of a marine engine must be done by an authorized dealer and must be certificated.

The engine choosed must comply current legislation.


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This post is also available in: Spanish

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