FIELD SERVICE NOTES · v0.1 · DRAFT — DO NOT TRUST PARTS YET2026.04.28
Four Winns H190 — OMC Cobra 4.3L
Battery replacement, parasitic-draw diagnosis, and spring commissioning startup. First-session diagnostic guide; engine and drive systems beyond the cranking/charging circuit are out of scope for this version.
HULL1989 Four Winns H190 Freedom · 19 ft · fiberglass open bow
HIN4WNTH065L889 (Dec 1988 build, 1989 MY)
ENGINEOMC Cobra 4.3L V6 · GM 262 ci · 2bbl · ~190 hp
ENGINE MOD432APRMED · S/N T1132957
DRIVEOMC Cobra · MOD 985685
OWNER / LOCS. Foran · Commerce Twp, MI · Oakland County
STORAGETrailer in driveway · cover on · last run fall 2025
BATTERYNAPA Legend Group 75 (automotive) · Jun 2018 · currently 3.0 V
DO NOW
Spring commissioning, cranking circuit only
// Fastest path: replace the wrong-group dead battery, find what drained it, prove the alternator before relying on it
Scrap the NAPA Legend. Group 75 automotive at 7.8 years discharged to 3 V — three independent reasons it's done. Recycle at any auto parts store ($10–25 core credit).
Buy a marine dual-purpose Group 24M or 27M, ≥650 CCA. Tier 1 in the parts list. Confirm dimensions fit existing battery box before purchase.
Before installing the new battery: test parasitic draw with the old corroded cables on the boat side, multimeter in series on the negative cable (Part 2 procedure). Expect <50 mA. Anything in hundreds of mA = active fault, find it before connecting the new battery.
Pull the cable boots back; inspect copper for green/black wicking up the strands (Part 3). Cut back to clean copper and re-terminate any contaminated cable.
Install new battery, start engine. Voltmeter at battery posts at idle and 1500–2000 RPM. Spec: 13.0–14.7 V. Outside this range = charging-system fault, do not run for the season.
// Note (v0.1 — first version)
No prior version. This guide is the initial diagnostic for this entity. Specs marked like this are unverified or memory-recalled values that need cross-check against OMC service manual 0507759 before being treated as authoritative.
PART 01BATTERY REPLACEMENT
Why this battery is done, and what to put in
Why the existing battery is unrecoverable
Three independent failure signals converge:
Voltage at 3.0 V. Nominal lead-acid is 12.6 V fully charged, ~10.5 V is the threshold below which smart chargers refuse to engage (this is exactly why your 1.5 A charger wouldn't start). At 0.5 V per cell the lead sulfate has crystallized into the hard, non-reversing form. Recovery probability to useful cold-cranking capacity: under 20% even with correct desulfation protocol.
Age 7.8 years. NAPA date code stamps show June 2018 manufacture (JU month / 8 year). Marine-duty service life on a flooded lead-acid is 4–6 years typical, occasionally 7. This unit was end-of-life before the discharge event.
Wrong group for marine duty. The label reads BCI Group 75 — a GM-pattern automotive side-post battery. Marine-rated dual-purpose batteries are Group 24M, 27M, 31M with top-post threaded studs, vibration-resistant construction, and USCG flame-arrestor venting. The Group 75 has been working in this boat because it physically fit the box, not because it's the right specification.
Coast Guard / insurance note
USCG 33 CFR 183.420 requires marine batteries to be installed with non-conductive securing means and protected from accidental short. An automotive battery that "fits" the box does not necessarily comply. If this boat were ever surveyed for insurance or sold, the Group 75 would be flagged.
Replacement spec
Marine dual-purpose, BCI Group 24M minimum, Group 27M preferred. Top-post threaded stud terminals. CCA ≥650 at 0°F to match what was in the boat. Reserve capacity ≥120 minutes (Group 24M typical) or ≥160 minutes (Group 27M typical).
Spec
Group 24M
Group 27M
Dimensions (L×W×H)
~10.25" × 6.81" × 8.88"
~12.06" × 6.81" × 8.88"
Weight (flooded)
~43 lb
~54 lb
Typical CCA
550–725
650–800
Reserve capacity
120–140 min
160–185 min
Cost (flooded, 2026)
~$110–150
~$140–200
Measure the box before buying
The Group 75 currently in the boat is roughly 9.06" × 7.06" × 7.5". Both Group 24M and 27M are taller, and Group 27M is significantly longer. Measure the existing battery box / tray / hold-down area before committing to 27M. If the box is sized for Group 24, a 27M won't fit without modification.
Acceptance test for the new battery
At install: open-circuit voltage 12.6–12.8 V (fully charged from new). After 24 hours installed in the boat with parasitic draw resolved: still 12.5+ V. Anything less = either the battery wasn't fully charged at sale (unlikely from a dealer), or there's still a draw on the boat side.
PART 02PARASITIC DRAW TEST
Find what drained the last battery before connecting the new one
The boat has no battery selector switch. Every always-hot circuit was connected to the old battery for ~6 months over winter. Whatever bled it to 3 V will bleed the next one to 3 V too. Quantify before commissioning.
Test setup
Tools: digital multimeter with DC current measurement, fused at minimum 10 A on the current-test path. Most decent DMMs (Fluke 87, Klein MM700, even a $40 AstroAI) have this.
Battery in the boat, all switches off (helm key out, accessory switches off, bilge selector to AUTO not MANUAL — this is the realistic stored state).
Disconnect the negative cable from the battery's negative post.
Set DMM to DC amps (A=, not A~), 10 A range, leads in the 10A jacks.
Connect black DMM lead to the negative battery post; connect red DMM lead to the disconnected negative cable lug.
Read the display. This is the parasitic draw.
Don't connect the meter at the wrong jack
DMMs in volts mode at the amps jack = blown fuse or blown meter. DMMs in amps mode at the volts terminals = direct short across battery through the meter. Verify both leads in the correct jacks (10A) and the dial set to A= before touching the battery.
What the reading means
Reading
Interpretation
0–20 mA
Clean. No always-hot loads. Battery will sit healthy through storage if disconnected isn't even necessary.
20–80 mA
Normal for a boat with bilge auto-float, depth finder memory, or aftermarket stereo. Acceptable for active-use season; over winter, will discharge a Group 24/27 in 3–6 months with no maintenance charging.
80–500 mA
Excessive. Active fault path. Will kill any battery over winter. Find and fix.
>500 mA / amps range
Severe. Something is actively drawing — likely a stuck bilge float pump cycling, or a chafed wire grounding to the hull. Find and fix immediately, do not leave connected.
If draw exceeds 80 mA, isolate it
With the meter still in series on the negative cable, pull fuses one at a time at the helm panel. The fuse whose removal drops the reading is the affected circuit. Common culprits on a 1989 H190:
Bilge pump (auto-float circuit) — by far the most likely. Float switch stuck closed by debris, partially submerged in residual bilge water, or contacts corroded into a low-resistance path.
Aftermarket stereo memory — only if a head unit was added with a yellow constant-12V wire. OEM 1989 wouldn't have one.
Courtesy / interior lights with ground fault — chafed wire shorting to a grounded surface, dim glow you don't see during the day.
Aftermarket depth finder / chartplotter standby — if any was added with constant-12V power.
Cheap, durable mitigation
Once the draw is quantified and the fault circuit is fixed, install a Blue Sea Systems m-Series single-circuit battery switch (~$30) on the negative cable. Lets you isolate the battery for storage or emergencies in two seconds. Boat with no master disconnect in 2026 is poor practice regardless of the parasitic-draw outcome.
PART 03BATTERY CABLE INSPECTION
Hidden cable corrosion is invisible until you load it
Visible corrosion at the battery posts is the symptom. Hidden corrosion under the cable insulation is the disease. Electrolyte mist from a flooded battery wicks up between the strands of the copper conductor, oxidizes the wire from the inside, and stays invisible until the cable's resistance climbs enough that voltage drops out under cranking load. Common on 30+ year old cables.
Inspection procedure (both cables, both ends)
Pull the rubber boot or heat-shrink back ~6 inches from each terminal lug.
Inspect the copper conductor itself, not just the lug crimp.
Look for: green wicking up the strands (copper sulfate), black tarnish, white crusty buildup, or strands fused together.
Flex the cable while watching the conductor. Brittleness or audible crunching = oxidized strands.
What to do with what you find
Finding
Action
Bright copper strands, flexible cable
Reuse. Clean lugs with a wire brush, spray with battery-terminal protectant, slide boot back.
Light tarnish, no green
Cut lug off, strip back to bright copper, re-crimp new tinned-marine ring terminal (Ancor or equivalent), heat-shrink with adhesive-lined tubing.
Green wicking >½" up the strands, or black core
Cable is contaminated past the lug. Cut back until you reach bright clean copper, re-terminate. If contamination extends >12" from the end: replace the cable entirely.
Brittle or crunchy strands, cable feels stiff
Replace the cable. Marine-grade tinned copper, AWG 2 or 1/0 for cranking cables on a 4.3L V6. Ancor or Cobra-brand marine cable.
Don't forget the ground end
The negative cable's far end terminates at the engine block (typically a starter mounting bolt or a dedicated ground stud on the bell housing). Common hidden-corrosion site on this generation. If the ground connection has resistance, you'll see strong battery voltage at rest, weak cranking under load, and a frustrating intermittent no-start condition that comes and goes with humidity.
PART 04CHARGING SYSTEM VERIFICATION
Prove the alternator before you trust it
The OMC Cobra 4.3L for 1989 came with a Motorola/Prestolite-style alternator, OMC P/N 0985465 / 0985466, rated 51 amps at 12 V, internal regulator. The alternator visible in your engine bay photo shows surface corrosion on the case but is in mounted position with belt installed. Whether it actually charges is unknown until measured.
Test procedure
New battery installed, parasitic draw resolved, fresh-water cooling muffs on the lower unit.
DMM on DC volts, leads on the battery posts directly (not at the helm gauge — gauge has wire-drop and is not the spec point).
Read battery voltage with engine off, key off: should be 12.6+ V on a fresh marine battery.
Start engine. Let idle 2 minutes to stabilize.
Read at idle: ~13.0–13.8 V typical.
Bring engine to 1500–2000 RPM. Read: spec is 13.0–14.7 V per OMC service manual 0507759 (cited via 1987 Cobra section, same charging-system generation; verify against 1989 issue before declaring authoritative).
Out-of-spec readings
Reading at 1500 RPM
Interpretation
<12.8 V
Alternator not charging at all — battery is supplying everything. Check belt tension, alternator field-wire connection, brushes/bearings if older.
12.8–13.0 V
Marginal. Charging some but undersupplying for accessories. Likely failing regulator or weak rotor. Won't keep up under load.
13.0–14.7 V
In spec. Healthy charging. New battery will be maintained.
>14.7 V
Regulator shorted or sense lead disconnected. Will overcharge new battery, boil electrolyte, destroy in weeks. Replace alternator or rebuild regulator before trusting.
Replacement alternator if needed
Stock unit replacements run ~$140–220 (ARCO 60125, Sierra 18-5957, or NLA Marine rebuilt OMC 985465). Higher-output upgrade options (Balmar 60-series at 70+ A) exist but are overkill for a 19 ft bowrider with no inverter or thirsty electronics. If the stock 51 A unit checks out, leave it alone.
Ancor 220203 (1/0 AWG) or 220204 (2 AWG), heat-shrink lined
Defender, West Marine, Amazon
$15–25 / pack
Heat-shrink tubing, marine adhesive-lined
Ancor or 3M EPS-300, 3:1 or 4:1, sized to cable + lug barrel
Defender, West Marine, Amazon
$10–18
Battery box / tray (if upsizing)
Sized for the new battery group; include hold-down strap
NAPA, West Marine
$15–35
Tier 3 — As needed (if Part 03 inspection says so)
Item
Spec / Part
Source
Cost
Replacement battery cable, 1/0 AWG marine tinned
Ancor 116205 or equivalent, sold by the foot
Defender, West Marine
$5–7 / ft
Replacement alternator (if charging fails Part 04)
ARCO 60125, Sierra 18-5957, or rebuilt OMC 985465
NLA Marine, Wholesale Marine, Amazon
$140–220
Bilge pump float switch (if Part 02 fingers it)
Rule-Mate RM450B or Johnson Pump 32-1503
Defender, West Marine, Amazon
$22–45
Minimum (Tier 1 only, assuming meter on hand): ~$120–215.
Tier 1 + Tier 2: ~$190–310.
Full session (Tier 1+2+3 worst case — new battery, cables, alternator, bilge switch): ~$400–600.
PART 06REFERENCES & SOURCES
Where every spec in this guide came from
Official manufacturer documentation
OMC Service Manual 0507759 — covers OMC Stern Drive 1989 4.3L (model family 432A___ED). Authoritative for charging-system spec, torque values, drive service procedures. Specific 1989 issue not yet held; cited values are from the 1986–1993 service manual generation.
OMC Parts Catalog 0985974 — 1989 4.3L Cobra parts. Authoritative for OEM part numbers (alternator 0985465/0985466, etc.).
OMC Cobra 1986–1993 Quick Reference Data — fluid capacities, oil viscosity by temperature range. PDF: discount-marine.com/sites/default/files/comment/omc-cobra-86-93-quick-references-data.pdf
HIN 4WNTH065L889: 4WN = Four Winns MIC, TH065 = hull serial, L = Dec, 8 = 1988 cert year, 89 = 1989 model year.
Engine MOD 432APRMED: 432 = 4.3L; A = major-change A; P = power steering equipped (confirmed by engine cover decal); R = right-hand rotation; MED = configuration suffix, full decode pending OMC documentation. Cross-reference: Crowley Marine parts lookup for sister model 432AMLMED = same family with mechanical steering / left-hand rotation.
OMC Service Manual 0507759 · Parts Catalog 0985974 · Owner's Manual 0985996.
NAPA 7575 — current battery in the boat (BCI Group 75, 800 CA / 650 CCA). Documented for the post-mortem; not for replacement.
Forum confirmations
iboats.com — "Over voltage charging on 4.3 OMC" — confirms OMC service manual charging spec 13.0–14.7 V at the alternator output (cited from 1987 Cobra service manual; same charging-system generation as 1989).
v0.1 (current, draft, 2026-04-28) — Initial guide. Scope: cranking-circuit spring commissioning only (battery, parasitic draw, cables, charging verification). Out of scope: fuel system, ignition, lower-unit service, water-pump impeller, drive bellows. Several spec values flagged UNVERIFIED pending direct OMC service manual 0507759 cross-check; these are memory-recalled or forum-cited values that need confirmation before being treated as authoritative. Styling is interim — rendered without canonical CSS source (template HTML source not retrievable in this session due to bash domain allowlist; structure follows the rendered template fetched via web_fetch). Pass to Claude Code for canonical styling render before publish.
END FIELD NOTES v0.1 · fourwinns-h190 · SF · APR 2026 · DRAFT