Hydrive OBKIT1 vs SeaStar HK6400
Commercial-rated hydraulic steering for singles to 300 hp and twins to 600 hp
OBKIT1 is Hydrive's most popular kit - the Admiral bullhorn that runs everything from family cuddy cabins to survey work boats. Against SeaStar's standard kit the ratings look similar on paper; the separation is the commercial rating, the commercial warranty, and again the carton: OBKIT1 lands complete, the HK6400 needs hoses added.
Side by side
Published manufacturer figures only. Where a maker doesn't publish a number, the table says so.
Max power (single)
Hydrive OBKIT1
300 hp
SeaStar HK6400A-3 / HK6400-4
350 hp
Max power (twin, counter-rotating)
Hydrive OBKIT1
600 hp total
SeaStar HK6400A-3 / HK6400-4
700 hp combined (600 on Dometic's current page)
Cylinder mount
Hydrive OBKIT1
Bullhorn (211BH) over the splashwell
SeaStar HK6400A-3 / HK6400-4
Front mount (HC5345-3) on the engine pivot plate
Wheel turns lock-to-lock
Hydrive OBKIT1
5.5 (4.4 with the optional 402 helm)
SeaStar HK6400A-3 / HK6400-4
5 (4.9 on HK6400-4)
In the box
Hydrive OBKIT1
401 helm, 211BH cylinder, 15 m tubing, 2 L ULTRA-15 fluid, fittings, bleeding kit
SeaStar HK6400A-3 / HK6400-4
1.7 cu in helm, HC5345-3 cylinder, 2 qt fluid - hoses sold separately
Commercial use
Hydrive OBKIT1
Commercial-rated, with the full 2-year warranty
SeaStar HK6400A-3 / HK6400-4
No commercial rating published; warranty drops to 1 year in commercial use
Engine-well clearance
Hydrive OBKIT1
540 mm
SeaStar HK6400A-3 / HK6400-4
Front mount - clearance set by the engine's pivot plate
Warranty
Hydrive OBKIT1
2 years, commercial and leisure use alike
SeaStar HK6400A-3 / HK6400-4
2 years, limited to 1 year for commercial, rental or income-producing use (Dometic warranty, Form 340124 Rev B)
Designed and supported from
Hydrive OBKIT1
Designed and manufactured in Adelaide, South Australia
SeaStar HK6400A-3 / HK6400-4
Dometic Marine, head office Richmond BC, Canada - per-product build location not published
| Specification | Hydrive OBKIT1 | SeaStar HK6400A-3 / HK6400-4 |
|---|---|---|
| Max power (single) | 300 hp | 350 hp |
| Max power (twin, counter-rotating) | 600 hp total | 700 hp combined (600 on Dometic's current page) |
| Cylinder mount | Bullhorn (211BH) over the splashwell | Front mount (HC5345-3) on the engine pivot plate |
| Wheel turns lock-to-lock | 5.5 (4.4 with the optional 402 helm) | 5 (4.9 on HK6400-4) |
| In the box | 401 helm, 211BH cylinder, 15 m tubing, 2 L ULTRA-15 fluid, fittings, bleeding kit | 1.7 cu in helm, HC5345-3 cylinder, 2 qt fluid - hoses sold separately |
| Commercial use | Commercial-rated, with the full 2-year warranty | No commercial rating published; warranty drops to 1 year in commercial use |
| Engine-well clearance | 540 mm | Front mount - clearance set by the engine's pivot plate |
| Warranty | 2 years, commercial and leisure use alike | 2 years, limited to 1 year for commercial, rental or income-producing use (Dometic warranty, Form 340124 Rev B) |
| Designed and supported from | Designed and manufactured in Adelaide, South Australia | Dometic Marine, head office Richmond BC, Canada - per-product build location not published |
Whatever the manufacturer's warranty says, both brands also carry Australian Consumer Law guarantees that can't be excluded - and for goods under $100,000 those apply to business buyers too.
Where OBKIT1 wins
- A commercial rating with the warranty to match: Hydrive's Admiral series carries its 2-year warranty for commercial and leisure use alike. Dometic's published warranty halves to 1 year the moment the boat earns income.
- Complete in one carton - 15 m tubing, fluid, fittings, bleeding kit. The HK6400 kits need hoses bought and sized separately.
- Engine-specific bullhorn variants (Honda, Mercury) and a COMPACT version for narrow wells - plus the OBKIT1-XT step to 350 hp singles and 1,200 hp twin rigs.
- Hydrive states its safety margins exceed Marine Survey Society requirements, and that every unit is individually tested rather than batch tested.
Credit where due
- Higher single-engine ceiling at 350 hp, and independent engine tilt on twins from the front-mount cylinder.
- Meets ABYC standards with NMMA certification.
- Optional dedicated 'Commercial' helm SKUs exist in the SeaStar component range (stainless shaft, upgraded top-plate seal) for those building a system from parts.
Our verdict
For a work boat, a hire boat or anything in survey, OBKIT1 is the straightforward call: commercial rating, full 2-year commercial warranty, complete kit. For a 350 hp recreational single, SeaStar's rating runs 50 hp higher than OBKIT1 - but so does Hydrive's own OBKIT1-XT, which we'd quote for that boat.
Questions we get asked
Is OBKIT1 accepted for commercial survey work?
OBKIT1 is Hydrive's commercial-rated kit and Hydrive states its safety margins exceed Marine Survey Society requirements. Survey acceptance is always the surveyor's call on the specific vessel, so tell us the boat and its survey class and we'll confirm the right spec with Hydrive before you buy.
What happens to the SeaStar warranty on a commercial boat?
Dometic's published warranty is 2 years for recreational use but limited to 1 year where the product is used commercially or in any rental or income-producing activity. Hydrive's Admiral series - including OBKIT1 - carries its 2-year warranty for commercial and leisure use alike.
More comparisons
- Hydrive COMKIT1 vs SeaStar HK6400
- Hydrive COMKIT6 vs SeaStar BayStar
- Hydrive OBKIT1-XT vs SeaStar PRO
- All Hydrive vs SeaStar comparisons
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