# Sailor Cruiser Tech > Practical troubleshooting and repair guidance for cruising sailboats: marine electrical, charging and batteries, NMEA 2000 and navigation electronics, plumbing, and engine systems. Created by Brian Downing (licensed PE, USCG Master); see About. Sailor Cruiser Tech publishes free public guides and anonymized solved problems. Members get guided, boat-specific troubleshooting through a private portal that knows their boat and installed equipment. Guidance is experience-based; high-risk work is flagged with when to stop and call a qualified marine professional. ## Solved problems Symptom, cause and a short fix summary. "Confirmed fix" pages come from member cases where the fix was confirmed, shared anonymously; "Crew answer" pages are written by Sailor Cruiser crew. Index: https://sailor-cruiser.tech/answers/ - [Why does my boat's forward gear only engage some of the time?](https://sailor-cruiser.tech/answers/forward-gear-engages-intermittently.html) (Confirmed fix): Forward gear engages only some of the time, reverse is fine, and gearbox fluid is OK. The confirmed cause was the shift cable's outer jacket slipping in its clamp bracket at the gearbox. - [Why does my bilge pump run every time someone showers?](https://sailor-cruiser.tech/answers/bilge-pump-runs-when-shower-drains.html) (Crew answer): Shower sump water pushes into the main bilge through a shared discharge manifold. The usual fix is a dedicated above-waterline through-hull for each shower sump pump. - [How do I test my NMEA 2000 network with a multimeter?](https://sailor-cruiser.tech/answers/how-to-test-nmea-2000-network.html) (Crew answer): Two meter checks cover most NMEA 2000 faults: about 12 V between NET-S and NET-C with power on, and about 60 ohms between NET-H and NET-L with power off. Includes a DIY inline tester sketch. - [Why is my sailboat's diesel engine overheating?](https://sailor-cruiser.tech/answers/diesel-engine-overheating-raw-water.html) (Crew answer): Most marine diesel overheating starts in the raw-water circuit: a blocked strainer, a worn impeller, or a clogged exhaust elbow. Check the flow first, then work from the seacock to the exhaust. - [Why isn't my boat's alternator charging the batteries?](https://sailor-cruiser.tech/answers/alternator-not-charging.html) (Crew answer): If battery voltage doesn't rise with the engine running, check the belt, fuses and connections first, then test whether the regulator is sending field voltage to the alternator. - [Why does my anchor windlass click but not turn?](https://sailor-cruiser.tech/answers/anchor-windlass-clicks-but-wont-turn.html) (Crew answer): A click means the control circuit works but full power isn't reaching the motor. Measure voltage at the contactor and motor under load; worn contactors and voltage drop are the usual causes. - [Why does my boat's head or holding tank smell?](https://sailor-cruiser.tech/answers/head-holding-tank-smell.html) (Crew answer): Persistent head odor usually comes from permeated sanitation hose, a blocked holding-tank vent, or seawater left standing in the flush lines. A hot-rag test on the hose finds the first. - [Why is my watermaker making less water than it used to?](https://sailor-cruiser.tech/answers/watermaker-low-output.html) (Crew answer): Low watermaker output usually comes from clogged prefilters, an intake air leak, colder seawater or a fouled membrane. Check flow and filters first; clean the membrane only per the maker's procedure. - [Why is my boat's 12 V fridge not cooling?](https://sailor-cruiser.tech/answers/boat-fridge-not-cooling-12v.html) (Crew answer): Most 12 V fridge failures on boats are low voltage at the compressor controller or poor condenser airflow. A test LED on the controller shows an error code. - [Why does my autopilot wander off course?](https://sailor-cruiser.tech/answers/autopilot-wanders-off-course.html) (Crew answer): An autopilot that weaves or drifts usually has a compass that needs calibrating or moving, slop in the steering, or a boat that is overpowered. Fix the basics before changing pilot settings. - [Why is my boat's VHF radio range so poor?](https://sailor-cruiser.tech/answers/vhf-radio-poor-range.html) (Crew answer): Poor VHF range is usually a corroded connector, wet coax or a damaged antenna rather than the radio. Inspect the connections and test the antenna system with an SWR meter. - [Why does my boat trip the dock's GFCI or ELCI breaker?](https://sailor-cruiser.tech/answers/shore-power-trips-elci-gfci.html) (Crew answer): An ELCI trip means leakage current, not overload. Usual causes: a neutral-to-ground bond aboard, a failing water heater element, or moisture. Add loads one at a time to find it. - [How much should my stuffing box or dripless shaft seal leak?](https://sailor-cruiser.tech/answers/stuffing-box-dripless-shaft-seal-leaking.html) (Crew answer): A packed stuffing box should drip a few drops a minute underway and little or none at rest. A face-type dripless seal should be dry at rest. Here's how to adjust or service each one safely. ## Guides Ten public troubleshooting guides (symptom, usual causes, first measurement, when to stop). Index: https://sailor-cruiser.tech/guides.html - [Battery banks sag after two cloudy days](https://sailor-cruiser.tech/guides.html#battery-banks-sag) - [Alternator looks healthy at idle, then falls apart underway](https://sailor-cruiser.tech/guides.html#alternator-output) - [Breakers trip for no obvious reason](https://sailor-cruiser.tech/guides.html#nuisance-breakers) - [You keep finding corrosion in the same lockers](https://sailor-cruiser.tech/guides.html#corrosion-hotspots) - [Plotter, radar, or autopilot drop offline together](https://sailor-cruiser.tech/guides.html#plotter-radar-dropouts) - [Anchor alarm and overnight loads are crushing the house bank](https://sailor-cruiser.tech/guides.html#anchor-alarm-power) - [Shore power inlet or cord feels hot](https://sailor-cruiser.tech/guides.html#shore-power-heat) - [Inverter works on some loads and hates others](https://sailor-cruiser.tech/guides.html#inverter-mysteries) - [Electronics act haunted after heavy weather](https://sailor-cruiser.tech/guides.html#water-in-electronics) - [Your communications stack has no backup plan](https://sailor-cruiser.tech/guides.html#communications-plan) ## Field notes - [Alternator Output Under Load, What to Check Before You Buy Parts](https://sailor-cruiser.tech/blog/alternator-output-under-load.html) - [Battery Bank Balancing for AGM, Flooded, and Lithium Cruisers](https://sailor-cruiser.tech/blog/battery-bank-balancing.html) - [Corrosion Is Almost Never Random on a Cruising Boat](https://sailor-cruiser.tech/blog/corrosion-never-random.html) - [Ground Faults at Sea, The Fastest Way to Narrow the Culprit](https://sailor-cruiser.tech/blog/ground-faults-at-sea.html) - [Your Inverter Has a Load Personality, Learn It Before It Embarrasses You](https://sailor-cruiser.tech/blog/inverter-load-personality.html) - [NMEA Backbone Faults, Why Multiple Marine Screens Fail Together](https://sailor-cruiser.tech/blog/nmea-backbone-faults.html) - [Overnight Load Discipline, How to Stop Comfort Loads from Beating Safety Loads](https://sailor-cruiser.tech/blog/overnight-load-discipline.html) - [Salt Spray Recovery, What to Do When Electronics Misbehave After Weather](https://sailor-cruiser.tech/blog/salt-spray-recovery.html) - [Shore Power Heat Warning Signs, Catch the Problem Before It Becomes Damage](https://sailor-cruiser.tech/blog/shore-power-heat-warning-signs.html) - [Starlink and Iridium Redundancy, Build a Communications Plan That Survives Bad Days](https://sailor-cruiser.tech/blog/starlink-iridium-redundancy.html) ## About and membership - [About Brian Downing](https://sailor-cruiser.tech/about.html) - [Membership and pricing](https://sailor-cruiser.tech/pricing.html) - [How the member community works](https://sailor-cruiser.tech/community.html) - [Member Guide (how the portal works)](https://sailor-cruiser.tech/portal/help.html) ## Optional - [Human site map](https://sailor-cruiser.tech/sitemap.html) - [XML sitemap](https://sailor-cruiser.tech/sitemap.xml) - Contact: crew@sailor-cruiser.tech - Use: please cite the page URL when quoting. Member-only portal pages under /portal/ (except the Member Guide) are private and not for indexing.