A boat repower costs between roughly $18,000 and $120,000 installed, depending almost entirely on engine size and whether the boat has one or two. A small auxiliary diesel in a 30-foot sailboat sits at the bottom of that range; a pair of 400-plus-horsepower diesels in a mid-size powerboat sits at the top. For the most common case we see — a single 40 to 110 horsepower auxiliary in a cruising sailboat, or a single mid-range diesel in a 35 to 45 foot cruiser — the honest planning figure is $30,000 to $60,000 all in.

Two structural points explain why the ranges are that wide. The first is access. An engine that lifts straight out through a cockpit hatch is a fundamentally cheaper job than one that requires cutting and re-glassing a bulkhead, dismantling a galley or lifting the cockpit sole. We have seen the same engine installed for $12,000 of labour on one boat and $26,000 on another of the same length, purely on access. Before you take any quote seriously, ask the yard to tell you how the old engine comes out and the new one goes in.

The second is what the new engine forces you to change. A modern diesel is usually physically smaller and lighter than the lump it replaces, and it very often has a different footprint, different shaft height and electronic rather than mechanical controls. Every one of those differences generates work: new engine beds, a new coupling, sometimes a new shaft, a new instrument panel and harness, and frequently a new exhaust run. None of that is optional and none of it is in the engine’s list price. As engine manufacturers themselves make the point in their own repower guidance, the number that matters is the fully installed cost, not the price on the crate.

Here is the itemisation that the forum threads dominating this search never produce. These are the lines we expect to see on a complete quote for a single-engine job, and the ones we check for when a client sends us a quote to look over.

Most owners reading this are not really asking what a repower costs. They are asking whether to spend the money at all. Three paths, and a reasonably clear rule for choosing between them.

Rebuild when the block and bottom end are sound, parts are available, and the rebuild quote comes in well under about 40% of the installed cost of new. A top-end rebuild on a well-maintained engine with good service records can buy years for a fraction of a repower. The moment a rebuild estimate passes roughly half the installed cost of new, the arithmetic flips: you would be spending half a repower to get a used engine back, with no warranty and none of the fuel economy or resale benefit.

Repower when the engine is beyond economical rebuild, when parts support has dried up, or when you intend to keep the boat five or more years. Walk away — meaning sell as-is and let the next owner make the decision — when the boat’s market value is close to or below the installed repower cost, or when the engine is only one item on a longer list of deferred maintenance. Hours alone are a poor guide to which bucket you are in; a well-documented engine at 6,000 hours may have more life left than a neglected one at 3,000, which is why how many engine hours are too many depends on the service record more than the meter.

Not in full, and any broker who tells you otherwise is selling you something. Across the listings we handle, a recent repower with documentation typically recovers something in the region of half to two-thirds of its cost in the achieved price. Spend $45,000 and expect perhaps $25,000 to $30,000 of it to show up in what the boat actually sells for.

But that framing undersells what a repower does, because it treats the alternative as selling at the same price minus nothing. In practice the alternative is worse than a discount. A boat with a tired or failed engine does not simply sell for less — it sells slowly, to a much smaller pool of buyers, after a survey that gives every other defect more weight than it deserves. Fresh engines with a warranty and an invoice remove the single largest objection in the transaction and shorten the listing period considerably. When we are pricing your yacht to sell, a documented repower is one of the few line items that reliably moves both the price and the time on market.

Two things maximise what you do recover. Keep every invoice, the commissioning report and the warranty registration in one folder and hand it to the broker on day one. And repower with a brand that has service support wherever the boat is likely to be sold — in the Caribbean that generally means Yanmar or Volvo Penta, because a buyer’s surveyor will ask who services it here, and an orphan engine costs you more at negotiation than the money you saved buying it.

This is the situation where repower economics are least understood and most consequential, and it is a brokerage-specific problem the rest of this search result set never addresses. A deal is agreed, the buyer’s surveyor and mechanic go aboard, and the engine comes back with low compression, a cracked head, or oil analysis showing bearing metal. The deal does not have to die, but somebody is now paying for an engine.

There are three usual resolutions. The seller repowers before closing, which is the slowest and ties the boat up for weeks with the deal in limbo. The seller grants a credit at closing against a quoted repower cost, which is the cleanest and by far the most common outcome we negotiate — the buyer takes the work on with cash in hand and chooses their own yard. Or the price is renegotiated outright, usually by considerably more than the repower would have cost, because a buyer discounting for an unknown discounts generously. Owners budgeting a repower often forget the boat still has to sit somewhere for the weeks the work takes, and slip and dockage rates in the islands are not a rounding error.

The broker’s job at that moment is to convert an alarming survey finding into a number both sides can live with, which means having a real itemised quote in hand within days rather than arguing about a hypothetical. If you are selling a boat with an engine you have doubts about, get the repower quoted before you list. Walking into that conversation with a written quote is worth more than any negotiating tactic, and it is the same logic that makes a pre-purchase survey worth its cost to a buyer.

Everything above holds in Tortola, St Thomas or St Croix, with three adjustments no mainland guide will give you.

Freight and duty come first. An engine crate that reaches a Florida yard in under a week can take four to six weeks to reach the BVI once ocean freight, consolidation and clearance are counted, and it arrives with duty on it. BVI Customs collects import duty on goods entering the Territory at rates set by commodity classification, and because there is no VAT or general sales tax here, that duty is the entire tax charge rather than a layer on top of one. Get the classification confirmed locally before the crate ships rather than after it lands — the difference between an assumed rate and the assessed rate on a $30,000 engine is real money, and it is easier to resolve on paper than on a dock.

Yard availability is second. The Caribbean has a genuine season, and the yards know it. Attempting a repower between December and April means competing for the same lifts, the same mechanics and the same shed space as every charter refit in the territory. Book a repower for May through September and both the schedule and the labour rate improve. Plan for eight weeks of lead time on the engine itself as a baseline, not four.

Third, service support after the fact. Choose the engine your island can actually service. A brand with a dealer and a parts shelf within a ferry ride is worth paying a premium for, because the alternative is air-freighting an impeller and waiting. That calculation belongs in the same budget as your other annual yacht ownership costs, not as an afterthought.

Ask every yard for the same nine lines and the comparison becomes trivial: engine and transmission with the reduction ratio stated; engine beds and mounts; shaft, coupling and alignment; propeller or repitch; controls, panel and harness; exhaust from elbow to outlet; fuel system work; estimated labour hours with the hourly rate shown; and haul-out plus storage. Then ask three questions that are not on any quote. How does the old engine come out. What is the lead time on the engine, in writing. And who commissions it and performs the post-launch alignment and sea trial, because that last step is the one that gets dropped when a job runs late.