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ENGINE MOUNT REPLACEMENT ON A YANMAR YSM-8 WITH ELLEBOGEN GT S40 MOUNTS

CASE STUDY: ENGINE MOUNT REPLACEMENT ON A YANMAR YSM-8 WITH ELLEBOGEN GT S40 MOUNTS

Sailboat: O’Day 28, moored in Dana Point, Southern California

Some information of the engine

The Yanmar YSM-8 is a small, single-cylinder marine diesel engine produced by Yanmar in the late 1970s and early 1980s. It was widely used in sailboats and small workboats due to its reliability, fuel efficiency, and durability.
The YSM series was an evolution of Yanmar’s earlier YS series and was designed for compact and reliable power in small marine applications.

The YSM-8 was produced alongside the YSM-12 (a slightly larger 12 HP model) and both were favored by boaters for their low fuel consumption, mechanical simplicity, and ability to run for long periods with minimal maintenance.

Technical Specifications

  • Model: Yanmar YSM-8
  • Type: Single-cylinder, 4-stroke, water-cooled diesel engine
  • Displacement:32 liters (318 cc)
  • Power Output: Approximately 8 HP (horsepower) at around 3,600 RPM
  • Cooling System: Raw water cooling
  • Fuel System: Mechanical fuel injection with a simple and robust design
  • Weight: Around 95 kg (210 lbs)

SOME INFORMATION ON THE SAILBOAT

The Beneteau First 26 is a fast and agile boat with a hull speed of around 6.4 knots.

Its generous sail plan and balanced design offer strong light-air and upwind performance. A spinnaker boosts downwind speed, making it competitive in club racing fleets. It’s well-equipped for sail control, yet easy to handle by beginners or shorthanded crews. With lines led aft and tiller steering, it’s ideal for confident solo or couple sailing.

Specifications

  • Length Overall (LOA): 28.25 ft (8.61 m)
  • Length at Waterline (LWL): 22.92 ft (6.99 m)
  • Beam: 10.25 ft (3.12 m) – providing a stable and roomy interio
  • Draft:
    – Shoal Keel Version: 3.25 ft (0.99 m) – suitable for shallow waters
    – Deep Keel Version: 4.67 ft (1.42 m) – better windward performance
  • Displacement: 7,300 lbs (3,311 kg)
  • Ballast: 2,400 lbs (1,089 kg) – lead ballast for stability
  • Sail Area: Approx. 372 sq ft (34.56 m²)
  • Rig Type: Masthead sloop – easy to handle and balanced

Construction & Design Features

  • Keel Type: Fin keel (deep or shoal draft options), offering a balance between stability and maneuverability.
  • Rudder: Spade rudder for responsive handling.

Interior & Comfort

  • Sleeping Capacity: Typically sleeps 4 to 5 people, making it ideal for small families or couples.
  • Cabin Layout: Features a V-berth forward, a main salon with settees, and a small galley.
  • Headroom: Approx. 6 feet (1.83 m), making it comfortable for most sailors.
  • Ventilation: Opening ports and a forward hatch provide good airflow.

Performance & Sailing Characteristics

  • Handling: The O’Day 28 is known for its forgiving and stable performance, making it a good choice for beginner to intermediate sailors.
  • Speed: While not a racing boat, it offers decent cruising speeds with a hull speed of about 6.4 knots.
  • Single-Handed Sailing: With proper rigging and an autopilot, it can be easily sailed solo.

INITIAL SITUATION OF THE ENGINE

The sailboat owner intends to clean the engine compartment and replace the old engine mounts. He stated, “Although not easily visible, the original mounts appear to have completely collapsed. It feels as if they provided almost no dampening effect, making the engine nearly mounted directly to the stringer.”

REPLACEMENT TO THE ELLEBOGEN GTS 40

Based on the technical characteristics of the YSM-8 engine, such as weight, position of mounts and position of the center of gravity (CoG), 4 mounts of the Ellebogen GT S40 were selected.  These mounts incorporate a high-damping compound, which is particularly beneficial for single-cylinder engines, helping to keep the engine steady. Below are the technical and dimensional characteristics.

VIDEO “AFTER”

Patrick recorded a video showcasing the engine’s condition with the newly installed mounts. Below is the footage demonstrating the engine with the Ellebogen GTS40 mounts

 

“I feel that the vibration is significantly less with the new mounts – although as a single cylinder diesel YSM-8 it will never be dead steady. I feel like the vibration transmitted to the vessel is significantly damped. For example my feet would feel vibration transmitted to the hull with the original mounts and I have no such sensation now with the new mounts.”

Mr. Patrick Fitzgibbon, Sailboat Owner.

IMPORTANT NOTES ON THE INSTALLATION

During the installation of the new engine mounts, Patrick encountered several challenges that required adjustments and improvisations:

Mount Height Adjustment:

The new mounts were taller than the original ones. Patrick, had to replace the original, thicker lower adjusting nut with a thinner jam nut to achieve the proper height.

Modification of Motor Mount Bracket:

The new mounts were taller than the original ones. Patrick, had to replace the original, thicker lower adjusting nut with a thinner jam nut to achieve the proper height.

Threading Issue with Stringer Bolts:

The most significant issue was with the original bolts securing the mounts to the boat’s stringer. These bolts had a section with no threads. He stacked the washers above the mount on the unthreaded portion of the bolt, so that when he tightened down the mount, the stacked washers allowed him to engage threads on those bolts. 

MORE INFORMATION ON THE GT mounts.

The Ellebogen GT mounts are universal marine engine mounts. They incorporate a failsafe interlocking metal part as shown on the below image.


This feature allows them to withstand high traction forces.


The mounts have undergone rigorous fatigue testing, ensuring optimal performance.

The metal parts are treated with Zinc Nickel allowing a salt spray resistance of 760H to the red corrosion and, on top of this, there is a double coat of PU black paint. This allows to obtain similar anticorrosive results to Stainless steel Aisi 304. More information on corrosion resistance click on this

LINK

If you have a similar application or engine do not hesitate to contact us.

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