Repower or replace an ageing Gili boat? The decision rule the desk applies is blunt: repower when the hull has verifiable structural life left and the business case needs only engines; replace when hull, systems and certification are all approaching their limits together, because bolting new engines to a tired boat buys eighteen good months at a third of a new boat’s price — and then hands you the same decision again with less money. The analysis is unsentimental and takes about a week to do properly. Here is how to run it.
Start with the hull, because engines cannot fix wood
The threshold question is structural: what is this hull actually worth as a platform for another five to ten years? For the typical hard-working timber or FRP Gili boat at 10–15 years old, that means an honest haul-out survey — fastenings, frames and floors around the engine beds, keel condition, plank or laminate integrity at the waterline, transom strength for the outboard loads. The survey verdict sorts boats into three bins:
- Sound platform: structure verified good, maintenance history real. Repower is on the table.
- Repairable with known cost: defined defects — refastening, floors, transom — priced alongside the repower. The combined bill is the number that competes with a new build, not the engine bill alone.
- Tired everywhere: widespread softness, corroded fastenings, a transom flexing under the current engines. Stop pricing engines; you are pricing sentiment.
Getting that verdict from an independent second opinion matters, because everyone else in the conversation sells something. The group’s own refit side — a refit bench that can honestly price the alternative — exists precisely so that the repair estimate and the new-build estimate can be compared without either desk marking its own homework.
The repower case, honestly costed
A twin-outboard repower on a Gili passenger boat is a well-understood project: engines, rigging, controls, gauges, propellers, usually new fuel plumbing and filtration, often a transom reinforcement, plus haul-out and trials. The engine invoice is typically only 70–80 percent of the true bill. What a proper repower buys: fuel burn per crossing commonly improves by double-digit percentages over worn engines of an older generation; reliability resets; and the boat re-enters service in weeks, not seasons. What it does not buy: a new hull, new wiring, new certification headroom, or a change in what the boat fundamentally is. The outboard-versus-inboard fork — and whether a repower is the moment to switch — is analysed in outboards or inboards for a Gili passenger boat.
The replacement case: what a new build actually competes on
A new hull competes on the lines the old boat cannot improve: certified passenger capacity matched to today’s demand rather than 2015’s; a hull form sized and powered for the current timetable, per the horsepower sizing logic; electrical, safety and guest-comfort systems designed rather than accreted; and a fresh certification and insurance baseline. Against that stand cost and time: a new Gili-class boat is a dry-season build programme with the budget bands published on the price and quote page, and the old boat must keep earning while the new one grows on its cradle — which, done deliberately, is exactly the transition plan: repower-lite maintenance on the old hull, new build contracted in the wet season, fleet swap at the following season’s start, old boat sold with her survey file while she still shows well.
The arithmetic that decides it
Put three five-year columns side by side and let the totals talk:
| Five-year view | Repower only | Repower + repairs | New build |
|---|---|---|---|
| Capital out | Engines + install | Engines + structural bill | Full build cost |
| Fuel per seat-crossing | Better than now | Better than now | Best (hull + engines matched) |
| Downtime risk | Hull-driven, rising | Reduced, not reset | Warranty-covered, lowest |
| Capacity/revenue ceiling | Unchanged | Unchanged | Re-specified to demand |
| Residual value at year 5 | Old hull, new-ish engines | Somewhat better | Mid-life modern boat |
Feed the columns with your real numbers — crossings per day, load factors, fuel prices, the seat revenue model from Gili tourist boat economics — and the decision usually stops being close. The pattern the desk sees repeatedly: boats under ten years with sound structure repower well; boats past twelve to fifteen hard seasons, or any boat whose survey opens the structural bin, argue for replacement the moment capacity growth or certification pressure enters the picture.
The mistakes that make either path expensive
Three recurring ones. Repowering on hope — skipping the haul-out survey because the engines are the visible problem; the transom was the actual problem, and the new engines found it. Over-powering the repower — bigger engines on a hull never designed for the thrust, trading a speed bump for structural fatigue and fuel burn. And replacing without a transition plan — signing a build contract with no bridge financing or fleet cover, so the business limps through a season with neither boat right. Each is avoided the same way: survey first, spreadsheet second, contract third.
Bring the desk the survey report and the operating numbers, and the repower-or-replace answer generally writes itself — and whichever way it lands, it lands as a plan with dates rather than a hope with engines.
Frequently Asked Questions
When does repowering an old boat make sense?
When an honest haul-out survey verifies the hull has structural life left and the business case needs only engines. Boats under ten years with sound structure repower well; the survey verdict comes first, because new engines bolted to a tired transom simply find the transom faster.
What does a repower really cost beyond the engines?
The engine invoice is typically only 70–80 percent of the true bill. Add rigging, controls, gauges, propellers, usually new fuel plumbing and filtration, often transom reinforcement, plus haul-out and trials. Price the complete project, and price any surveyed structural repairs alongside it.
What does a new build offer that a repower cannot?
Everything the old hull fixed at its launch: certified passenger capacity matched to today’s demand, a hull form and power matched to the current timetable, designed rather than accreted electrical and safety systems, a fresh certification and insurance baseline, and warranty-covered reliability.
How do you keep earning during a replacement build?
Plan the transition deliberately: light maintenance keeps the old boat serving while the new hull is contracted in the wet season and built through the dry, the fleet swaps at the following season’s start, and the old boat sells with her survey file while she still shows well.