Fast triage before turning wrenches

Start with safety: ventilate, kill ignition sources, and confirm the raw‑water seacock is open and the strainer isn’t packed with eelgrass or plastic—overheats happen fast and shutdowns are doing you a favor, not ruining your day. Flip or reset the genset’s DC control breaker if it has one, because one tripped little switch can make a healthy unit act stone‑dead, and try the local panel at the generator to bypass long helm wiring runs that love to corrode in Miami humidity. If you recently had an automatic stop, assume it was legit—check oil level/pressure, coolant, and seawater flow first, then restart only after you know the protections aren’t screaming for a reason.

No crank: dead button, maybe a click

When the start button does nothing (or just clicks), nine times out of ten the fault is battery state, cabling, ground, or the starter relay/solenoid—start power, not engine health. I carry a pulse tester and a clamp meter; in a lot behind Coconut Grove last summer, a Sea Ray 320 lit up strong at 12.7V static but sagged under load because a corroded ground lug behind the genset was green mush under heat‑shrink—cleaned, crimped, and it cranked like it meant it, no new parts needed. If helm start is flaky, walk to the unit and use the onboard panel; that trick alone has “fixed” more than one supposed starter failure by skipping a tired remote switch or a sketchy harness. When you do have solid power at the solenoid and still no engagement, tap‑test won’t save you for long—plan on a relay/solenoid swap and keep spares in the dock box, because waiting till Sunday afternoon is how tows get booked.

Cranks but won’t start: fuel first, then air, then the obvious

If it spins but refuses to fire, bet on fuel delivery—primary/secondary filters, lift pump action, and air leaks on the suction side put more boats on trailers than “mystery electronics” ever did. I bled a Northern Lights 9kW off Dinner Key last June for Carlos’s Bayliner 285; bubbles at the bleed screw told the story before the smell did, so two new filters, a new O‑ring, and snugged clamps got it back online in under an hour, and he skipped a $1,200 wild‑goose ECM order that another shop pitched over the phone. For diesel, don’t forget preheat/glow—weak batteries can turn the engine but starve the glow plugs; for gasoline sets that sat, varnished carbs from ethanol fuel are common, and a cleaner shot can wake one up long enough to get home, but the real fix is a full clean and a better fuel routine. If the tank’s been sitting warm through a Miami summer thunderstorm cycle, assume water and phase separation have your number—fresh fuel beats magic in a bottle every time, and filter bowls will rat you out if you try to pretend otherwise.

Starts then dies: treat it like a protective shutdown

Catching and quitting is usually the engine saving itself—low oil pressure or high temp triggers are supposed to shut you down, and bypassing them is how you buy a rebuild you didn’t budget for. The quickest tell: put a hand on the water‑lift muffler—it should be warm, not branding‑iron hot; if it’s too hot, head straight for seawater flow checks: strainer basket, impeller vanes, and whether the seacock or intake is fouled enough to choke a manatee (seen it, not kidding). I keep impellers and cover gaskets in the truck; changing one at Bahia Mar for Sofia’s Tiara 380 last August turned a “call a diver” situation into a 40‑minute dockside win, and the only mystery was why the old vanes were still expected to do laps after three seasons. If the muffler’s warm and temps look normal but it keeps quitting, inspect the shutdown circuit connectors and the oil/temperature sender leads—loose, oxidized spades in that loop can fake a trip and make you chase fuel ghosts for hours.

Runs fine but no power: not a no‑start, still worth two minutes

It’s not the same problem, but it feels like it at midnight when the cabin’s dark and the fridge clicks off—engine runs, panel shows nothing. Before blaming the control board, confirm the generator’s AC breaker and your source selector; if those are right, a long‑idle unit may have lost residual magnetism and needs a proper “flash” per the manual or a pro—don’t wing that step with YouTube and jumper cables. Regular exercise under load prevents this surprise and keeps the alternator section honest, which is one more reason I nag owners to run the set like they mean it, not five minutes at anchor just to “hear it”.

Miami jobs that repeat: what fails, how I fix it, and what it costs

I put this table together from jobs I’ve seen in Miami and Fort Lauderdale the past few seasons—Bahia Mar, Dinner Key, Haulover, you name it—and it’s where most of the “marine generator won’t start” calls land, cost‑wise and time‑wise.

Symptom	Likely Cause	Field Fix I Use	Typical Cost (parts+labor)	DIY vs Call
No crank	Weak battery, corroded ground, tripped DC control breaker	Clean/retorque lugs and grounds, reset breaker, test at local panel, swap starter relay if needed	$150–$500 if cabling/relay; $200–$350 battery	DIY if comfortable; call if starter drags
Cranks no start (diesel)	Clogged filters, air in suction side, dead lift pump	Replace primary/secondary filters, bleed at secondary/injection pump, confirm lift pump action	$180–$450 filters+bleed; $250–$600 lift pump	DIY filters/bleed; call for pump/injection
Cranks no start (gas)	Varnished carb, stale ethanol fuel	Temporary carb cleaner, full carb clean at dock, refresh fuel	$120–$400 clean; $300–$800 rebuild	DIY temporary; shop for full clean
Starts then dies	Overheat (no seawater flow), low oil pressure	Clean strainer, replace impeller, verify seacock/through‑hull, check oil level/pressure	$90–$250 strainer/impeller; more if blocked intake	DIY strainer/impeller; call for intake/sensors
Runs, no AC power	Lost residual magnetism, open output breaker	Verify breakers/source select; perform OEM‑specified flash	$0–$300 simple; ECU/VRD is more	Call unless OEM procedure is known

On the water, the fastest win is starting with power, fuel, air, and cooling—keep the multimeter, spare filters, a short bleed hose, a fresh impeller, and the right sockets in a small bag and half your weekend “mysteries” evaporate before dock lines even slacken.

FAQ

South Florida notes from the truck

Salt air and marina humidity eat small DC connectors first, not just big battery lugs—those tiny shutdown circuit spades are why a generator that ran fine at Bahia Mar suddenly quits at Nixon Sandbar and won’t come back without a wiggle and a clean. Exercise the unit under real load—microwave, water heater, air‑con—so you don’t lose residual magnetism and so fuel keeps moving, because short no‑load runs are theater and won’t prevent the 2 a.m. “it died again” call. If your marine generator won’t start after a squall line rolls through, think water and bad fuel first, then filters and clamps, and only then point a finger at the magical black box with the expensive sticker. I hate seeing owners spend $800 on parts darts when a $12 O‑ring and a proper bleed at the secondary would’ve had them making coffee at anchor fifteen minutes later. Weird? Not really—“marine generator won’t start” is a phrase that usually means “maintenance was shy and the calendar finally won,” and South Florida seasons don’t forgive storage shortcuts.

What I actually do on a dock call (and why)

I start with what I can see and touch without tools: seacock position, strainer basket, oil level, coolant bottle, and the little red or black DC breaker on or near the genset—because those are fast and free, and they solve more than owners expect. Then the meter comes out: battery voltage, cranking drop, confirmation at the solenoid, and a leap past the helm button to the local panel when it’s even slightly suspect, which in briny harnesses is… often. For cranks‑no‑start, I change filters first and bleed with the lift pump energized or the manual lever; bubbles at the bleed tell me to chase suction side leaks before I start talking injectors or sending units out for bench testing. If the story is “it starts, then dies,” I touch the muffler, pop the strainer, and if I find rubber confetti in the pump, we do an impeller with a fresh cover gasket and go for a test run on real load, not just idle hum in the slip. And if it runs but the panel’s dark, I check breakers, source selection, and the manual on flashing—because “marine generator won’t start” calls sometimes hide an electrical output problem the engine can’t fix by itself.

A last word that isn’t cute

Run it like you use it, not like you want to ignore it, because “marine generator won’t start” is less a surprise and more a calendar reminder that got snoozed too many times. Fresh fuel, clean strainers, tight grounds, and exercise under load will keep you from shaking me awake at 11 p.m., which, honestly, I’m fine with—sleep’s cheaper than emergency rates and tow bills