Mercury FourStroke 3.5HP MLH

When space and weight is at a premium and you need reliable portable power from your outboard engine, Mercury offer a range of extremely light and robust four stroke outboard engines, including the 3.5hp model which is available in short or long shaft versions.

Simple to install and lightweight, the Mercury 3.5hp outboard is portable for most leisure users. Weighing just 17kg, the Mercury F3.5M is a suitable outboard engine for our VY27 PVC or Hypalon inflatable boats where top speed is less important than size and weight. The F3.5L (Long Shaft) is not suitable for use on Storm Inflatables but can be used as an auxiliary engine on our RIBs.

For outboard engines in this horsepower range, portability is key and Mercury’s 3.5hp FourStroke is among the lightest outboards in the class. Every Mercury portable FourStroke is packed full of features, such as an automatic reverse locking system and convenient integral fuel tanks.

The Mercury 3.5hp FourStroke undergoes the same corrosion resistance processes as used in higher horsepower products. With a low weight and conveniently positioned large grip carrying handles, getting the power to your inflatable is not a problem.

The 3.5HP 3.5MLH Mercury boat motors are equipped with a 20-inch long shaft, tiller steering, and manual start. Ideal for small canoes, tenders, and small inflatables. This motor, weighing just 43 lbs., is compact and truly portable with its ergonomic carry handle, setting it apart in the same HP class. It also features a larger carburetor for increased performance.

But the trusty portable 3.5 hp Mercury outboard didn’t miss a beat and we trolled downstream, with just the occasional puff of oil smoke to keep us company. My tiller arm was getting a workout from the transmitted vibration — “Who needs to go to a gym?”, I thought to myself — but in all fairness, the Mercury 3.3 was never designed for extended trolling periods.

We kept that Mercury for some time, putting all around the southern end of Lake Macquarie and enjoying the pleasures of simple boating. And when we borrowed the Mercury Mariner 3.5 hp version several years later, we experienced those same pleasures all over again.

Made in Japan, the Mercury 3.5 outboard motor develops 3.5hp at 5000rpm from its 74.6cc, loop-charged, single-cylinder powerhead, with a wide open throttle rpm range of 4500-5500. The Mercury 3.5 hp outboard fuel mixture of normal 50:1 premix means the engine’s single piston ring would last very well, and the fixed ignition timing works well above a two-thirds throttle opening.

The Mercury 3.5 engine’s OEDA zero-star emissions rating does mean it’s pretty dirty, but considering the small amount of fuel it uses, that might not be such a consideration.

The deep 2.15:1 gear ratio improves thrust efficiency at displacement speeds using the standard 5.7in pitch plastic weedless prop. The Mercury 3.5 hp outboard weight of 13kg (dry weight) is made even more attractive by the addition of a large carry handle. There are four trim positions, a full-tilt locking knob and a reasonably large 1.4L fuel tank that gravity feeds to the single-jet carbie.

Given the upper cowl completely unclips from the lower, with a separate spark-plug hatch fitted, maintaining the 3.5 is nice and easy.

Mercury recommends servicing the 3.3 hp every 100 hours, or annually after the first service at 20 hours. The recreational-usage warranty is for five years, provided the engine is maintained by an authorised Mercury service centre.