Irwin 10/4
Built 1975–1982 by Irwin Yacht & Marine Corporation
About the Irwin 10/4
Researched from public sources for this model. Any individual boat may have been modified or repowered — confirm before relying on any figure.
- Built
- 1975–1982
- Builder
- Irwin Yacht & Marine Corporation
- Designer
- Ted Irwin, Walter Scott
- Length
- 25.33 ft
- Waterline
- 21.83 ft
- Beam
- 10.33 ft
- Draft
- 2.75 ft
- Displacement
- 7,000 lb
- Ballast
- 2,000 lb
- Hull / keel
- centerboard
- Rig
- cutter
- Propulsion
- inboard
- Stern thruster
- not fitted
Tank capacities — where the figures come from
-
Fuel unknown
“20 U.S. gallons (76 L; 17 imp gal)” — search excerpt, en.wikipedia.orgWikipedia, citing a spec database in 2021, says 20 gal, while our earlier figure from that same database was 15 gal. No builder or owners' association source was found to settle it.
-
Water unknown
“capacity of 45” — search excerpt, en.wikipedia.org · “Water Tank 40 gal” — broker listing, sailingtexas.comWikipedia, drawing on a spec database, says 45 gal; one sale listing says 40.
-
Holding unknown
“holding tank 15gal” — broker listing, sailingtexas.comOne sale listing only.
-
Water heater unknown
No builder specification, option list or owner report on a water heater found for this 25 ft trailerable cruiser.
Tanks are often replaced or added on older boats — check the tank labels or a survey for yours.
Thrusters and steering — where this comes from
-
Bow thruster unknown
No source found either way.
-
Stern thruster not fitted
Our earlier figure of none has no source, and nothing was found either way.
-
Steering unknown
No builder document for the 10/4 was found (Irwin's surviving 1977 standards sheets cover only the 28-52 models), and Wikipedia gives only the spade rudder. Our earlier figure of wheel steering has no source.
Thrusters and steering are often replaced — check the units on your boat before ordering parts.
Sources disagree on engines, fuel tank, water tank — left blank rather than guessed.
Beamy (10 ft 4 in, hence the name) shoal-draft keel/centerboard cutter; draft 2.75 ft board up, 6.67 ft board down. Many were fitted with a small Yanmar diesel (YSB8), which owners call reliable but marginal for a 7,000 lb boat. Only a single lower shroud per side; some owners add a babystay or double lowers. The shallow rudder can be overpowered. Water tank size not found.
Engines fitted
-
Yanmar 8 hp diesel (model not named by source) — 8 hp, diesel, single
standard
Wikipedia: inboard Yanmar diesel of 8 hp or a Universal Atomic 2 gas engine; built 1975-82.Sources: en.wikipedia.org
-
Atomic 4 (Universal) Atomic 2 — gas, single
factory option
Wikipedia lists the Universal Atomic 2 gas inboard as the alternative to the Yanmar.Sources: en.wikipedia.org
Boats of the same model can differ — check which engines yours actually has before ordering parts.
Known problems for this model
-
Wet plywood-cored deck deck
An owner notes the deck is cored with plywood, so leaks at fittings can rot the core; sound the deck before buying.sailnet.com
-
Centerboard pivot and pendant hull
The board's pendant cable breaks and is awkward to replace inside the narrow trunk, and the stainless pivot pin epoxied into the keel can work loose through the glass.sailnet.com
-
Rusting steel mast-support beam rigging
The shrouds load a steel I-beam that rusts out of sight; one boat reportedly lost its mast when the beam failed. Some boats have a wooden compression post that can sit in bilge water, and the mast step tends to leak.sailnet.com
-
Leaking portlights and rotted bowsprit deck
Owners report the portlights leak as a rule, and the plywood-cored bowsprit can rot and need rebuilding.sailnet.com
-
Exhaust elbow and manifold corrosion exhaust
On the small Yanmar, the exhaust elbow, downpipe and manifold tend to rust together and are usually replaced as a set.sailnet.com
Engines & parts
Universal Atomic 4 parts: good
Factory optional engine — you entered “Atomic 4 (Universal) Atomic 2”
Tens of thousands were built (sources say from 40,000 to 50,000). Despite being out of production for decades, the engine is well supported: Moyer Marine sells parts, rebuilt engines, fuel pump rebuilds and exhaust parts, and hosts an owners' forum; Old Lyme Marina and others also supply parts, and electronic ignition upgrades are available.
Parts sources: Moyer Marine
Common problems (3)
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Raw-water cooling scale and corrosion cooling
Most Atomic 4s are raw-water cooled, so the block scales up and corrodes, especially in salt water; cranking without starting can also flood the engine with seawater through the exhaust.goodoldboat.com · moyermarineforum.com · keelindex.com
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Gasoline vapor fire/explosion risk fuel
Gasoline vapor is heavier than air and settles in the bilge, so ventilation, blower use and shutting the fuel valve (a stuck carburetor float can overflow) matter.goodoldboat.com
-
Ignition and fuel system faults electrical
Points, condenser, cap and wires, plus gummed carburetors and contaminated fuel, are the most common reasons an Atomic 4 won't run well.keelindex.com · goodoldboat.com
Maker’s service schedule (9)
| Engine oil & filter change | 50 hrs | “3. FIFTY HOUR CHECK a. Using sump pump, remove all oil from crankcase. Refill with a good grade oil as specified in Tabl” — manufacturer, westerbeke.com |
| Fuel filters & water separator | 50 hrs | “e. Clean fuel pump strainer.” — manufacturer, westerbeke.com |
| Heat exchanger & oil cooler cleaning | 50 hrs | “b. Inspect oil cooler and remove any accumulation of grit or dirt.” — manufacturer, westerbeke.com |
| Clean flame arrestor | 100 hrs | “b. Inspect flame arrestor to be sure air passages are clean and free from oil. If dirty remove and wash with kerosene.” — manufacturer, westerbeke.com |
| Check clutch (reverse gear) adjustment | 100 hrs | “4. ONE HUNDRED HOUR CHECK ... c. Check adjustment of clutch.” — manufacturer, westerbeke.com |
| Valve clearance check / adjust | 150 hrs or 1 yr | “5. ONE HUNDRED FIFTY HOUR CHECK a. Check valve tappet adjustment.” — manufacturer, westerbeke.com |
| Spark plugs inspect / replace | 150 hrs | “b. Remove, clean, and reset spark plugs.” — manufacturer, westerbeke.com |
| Transmission fluid change Universal V-drive unit (V-drive installations only; the standard reverse gear shares engine oil) | 500 hrs | “(2) After the first 50 hours of operation, drain unit and refill ... (3) Change lubricant every 500 hours of operation.” — manufacturer, westerbeke.com |
| Complete overhaul | 3,000 hrs | “At the end of three thousand hours of operation the engine should be completely overhauled.” — manufacturer, westerbeke.com |
Service part numbers (8)
| Oil filter optional add-on oil filter (not standard equipment) |
Universal 276236 | “2 Element or Cartridge 1 276236 (Oil Group, Oil Filter, Not Standard Equipment)” — manufacturer, westerbeke.com |
| Raw-water impeller Oberdorfer N202M-03 / N202M-07 replacement raw-water pump (Universal pump 295625) |
Oberdorfer 6593 | “5 Impeller 6593 6593 6593 6593 6593 1 (N202M, N202M-03, N202M-07 parts list)” — manufacturer, pumpsandpartsonline.com · “Impeller : Catalog # 6593, Impeller” — dealer, pumpagents.com |
| Raw-water pump kit Oberdorfer N202M-03 / N202M-07 raw-water pump |
Oberdorfer 10725 | “REPAIR KIT N202M N202M-03 N202M-07 10725” — manufacturer, pumpsandpartsonline.com · “Catalog # 10725, Repair Kit, includes O-Ring, Snap Ring, Impeller, 2 x Lip Seal” — dealer, pumpagents.com |
| Drive belt alternator belt (Prestolite and Motorola alternators) |
Universal 239387 | “19 Belt 1 239387 (12 Volt - Motorola 51 Amp Alternator)” — manufacturer, westerbeke.com |
| Spark plug | Universal 273276 × 4 | “8 Spark plugs, champion 4 273276” — manufacturer, westerbeke.com |
| Thermostat late style, from 1967 / serial #79476 (Holley 145 F, on cylinder head) |
Universal 200206 | “12 Thermostat Kit 1 200206 consists of 262278 and 261601” — manufacturer, westerbeke.com |
| Thermostat Dole type, before serial #79476 (on manifold) |
Universal 200207 | “13 Kit, Thermostat (consists of 275965 & 261144) 1 200207” — manufacturer, westerbeke.com |
| Zinc / anode fresh-water-cooled engines only (Universal heat-exchanger kit) |
Universal 299760 | “23 zinc pencil 1 299760 (Cooling, Fresh Water System, after serial #79476)” — manufacturer, westerbeke.com |
From the engine maker’s parts lists, or two independent parts dealers. Numbers change with serial number and get superseded — check yours before ordering.
Sources disagree on first year, last year, number built — left blank rather than guessed.
Model sources (4)
sailboatdata.com · sailnet.com · en.wikipedia.org · sailingtexas.com
Other Irwin models
- Irwin 30 Citation 1977–?
- Irwin 37 1971–1982
Researched from public sources. Spotted an error? The sources are listed above — tell us what they got wrong.