Choosing a marine engine starts with a basic question: what are you actually trying to push through the water? A full-size vessel needs serious inboard power, while an RC model needs a compact four-stroke that sips nitro and glow fuel. The two engines here sit at opposite ends of the propulsion spectrum, so the right pick depends entirely on the scale of your project and the budget you're working with.
Quick Verdict
If you're repowering or restoring a real boat, the Yanmar 4LHA-STZP is the only realistic option of the pair. It delivers 200 HP from a four-stroke diesel built for continuous marine use. If your project is a model boat, the OS Max FS-61 is the practical choice at a fraction of the price and in fresh new condition.
At a Glance
| Yanmar 4LHA-STZP | OS Max FS-61 | |
|---|---|---|
| Price | USD 15,000 | USD 450 |
| Condition | Used | New |
| Engine type | Four-stroke diesel | Four-stroke glow/nitro |
| Origin | Japan | Japan |
| Best for | Full-size inboard propulsion | RC model propulsion |
Where Each Product Wins
- Yanmar 4LHA-STZP wins for anyone who needs genuine marine propulsion power. The 200 HP rating and four-stroke diesel design are aimed at a real inboard installation, not a toy. It's the kind of engine you'd expect to find in a project boat that needs dependable thrust.
- OS Max FS-61 wins for hobbyists who want a new, ready-to-run four-stroke for an RC hull. At $450, it's an accessible entry point, and the new condition means you won't have to immediately worry about wear from a previous owner.
Product Notes
Yanmar 4LHA-STZP
The Yanmar 4LHA-STZP is a used, 200 HP inboard marine diesel engine from Japan. This is a serious piece of machinery, and the price reflects that: USD 15,000. If you're refitting a boat that needs a reliable, high-powered diesel, this is the direction to go. The four-stroke design is meant for sustained operation, and the Yanmar name carries weight in marine circles, though we're not going to lean on brand reputation here. The obvious limitation is the used condition and the lack of any warranty, so you'll want to budget for a careful pre-purchase inspection before you commit. The engine is described as tested ok, but that's not the same as a guarantee. This engine is for a real boat, not a model.
OS Max FS-61
If your project is a model boat, the OS Max FS-61 is a neat little four-stroke engine that runs on nitro and glow fuel. It's new in the box, which is a big plus at this price point-USD 450-and it comes with manual, stickers, and paperwork. The engine is designed for inboard RC marine use, though the compatibility notes also mention aircraft, so it might be worth checking your specific hull setup before ordering. The main drawback is the sale is final and there are no returns. The box has some scuffing, but the engine itself is described as new. For a hobbyist building an RC boat, this is a compact, affordable four-stroke option that won't overwhelm a small hull.
Final Choice by Use Case
For a full-size boat that needs inboard diesel power, the Yanmar 4LHA-STZP is the clear choice. For an RC model that needs a fresh four-stroke engine, the OS Max FS-61 is the one to grab. There's no true head-to-head overlap-the decision comes down to whether you're working on a real vessel or a scale model. In terms of marine engines propulsion, these two serve completely different captains.
