PRODUCT DETAILS
4HP / 5HP Mariner Outboard Base Gasket – JAPAN Models Only (2-Stroke)
Replaces 27-91780 / 91780M – Yamaha-Built Mariner – UK Stock
Product Description
Base gasket for Mariner 4HP and 5HP 2-stroke outboards, Japan-built models made by Yamaha. These engines have serial numbers starting with 6E0 or 6E3 and share many parts with Yamaha’s 4A and 5C series.
This gasket fits between the powerhead and the midsection to properly seal the lower end of the engine. High-quality aftermarket part with OEM-style fit.
Fitment
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Mariner 4HP / 5HP
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2-Stroke
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Japan models only
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Serial number starts with 6E0 or 6E3
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Based on Yamaha 4A / 5C design
Will NOT fit Mariner engines made by Mercury USA or Belgium.
Replaces Mariner Part Numbers
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27-91780
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27-91780M
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91780
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91780M
Why Buy from SSI MARINE?
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All parts are stocked in the UK
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Selected by marine technicians for fit and quality
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Same-day dispatch before 1 PM (Mon–Fri)
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Collection available from our Leigh (Manchester) workshop
If you're unsure about compatibility, contact us with your serial number and we’ll confirm the fit.
Shipping & Collection
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Tracked 24-hour UK delivery
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Same-day dispatch before 1 PM
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In-person collection available Monday to Friday
SHIPPING & DELIVERY
Delivery & Returns Policy
Delivery
Standard Delivery
- £6: Royal Mail Tracked 24 Service
- £3.99: Large Letter - Royal Mail 1st Class Post (Untracked)
We offer free delivery on all orders over £150 (excludes outboard engines).
Orders placed before 1:00 PM (Monday-Friday) are usually dispatched the same working day.
Most parcels are delivered within 24 hours, but please allow extra time for courier delays that may occur outside our control.
For outboard engines, please contact us for a delivery quote.
Important: Please ensure your shipping address is correct before completing checkout. SSI Marine is not responsible for parcels sent to an incorrect address provided by the buyer.
Tracking Your Order
Once your order has been dispatched, you will receive a tracking number via email (after 5 PM on the day of dispatch).
Tracking is available only for parcels sent via Royal Mail Tracked 24.
Large Letter orders are sent via Royal Mail 1st Class Post (untracked).
Returns
We accept returns of unused and undamaged items within 30 days of purchase.
Returned items must be in sellable condition and include the original packaging.
Please do not tape, label, or write directly on the product's original box.
Important: Do not return items in their original product boxes only, they must be placed inside a protective outer box or bag. Parcels returned like the example below will be subject to a 20% restocking fee.
Return shipping costs are the customer's responsibility.
Please include your order details and reason for return inside the parcel.
Refunds
Refunds are issued for the item purchase price only (shipping costs are non-refundable).
All refunds will be made using the same payment method as your original order.
Items returned in poor condition or without proper packaging may incur a 20% restocking fee.
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