ARCO 57-MBK450 Starter Mounting Bolt Kit – Gear Reduction Marine Starters
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ARCO 57-MBK450 Starter Mounting Bolt Kit
Complete your gear reduction starter swap with the right hardware. The ARCO 57-MBK450 includes two long 3/8–16 N.C. thread mounting bolts specifically sized for installing gear reduction starters on marine inboard and stern-drive engines. Using the correct mounting hardware ensures a secure, properly aligned installation that protects both the starter and the engine block.
Compatible Applications
- ARCO gear reduction starters with staggered bolt mounting pattern
- Delco gear reduction starters with staggered bolt mounting pattern
- Marine inboard and stern-drive engines with 3/8–16 N.C. thread starter mounting
- Not compatible: metric-threaded engine blocks or 10MT-style starters
Specifications
- Includes: 2 long mounting bolts
- Thread: 3/8–16 N.C. (National Coarse)
Parts Desk Insights
This kit is essential when upgrading from an older 10MT-style starter to a modern gear reduction unit. Gear reduction starters use a different bolt spacing and length than 10MT starters — the factory bolts from the old unit will not work, and attempting to reuse them risks a misaligned or insecure installation. Confirm your engine block uses standard N.C. thread before ordering; metric-threaded blocks require different hardware. If you also need a solenoid for your gear reduction starter installation, see the ARCO SW450 Starter Solenoid for MerCruiser, Cobra & Volvo Penta or the ARCO SW463 Heavy-Duty Starter Solenoid for MerCruiser, OMC & Volvo Penta.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.