Product reviews

Mariner 3.5hp Review

The Mariner 3.5hp outboard is the second lowest output engine in the Mariner 4 stroke range. The 2.5hp outboard is the same engine but de-tuned via the carb. These small engines are also used on a regular basis as auxiliaries to the boats main power source.

I purchased the outboard from Splash Marine on Trafford Park. I checked some of the bigger players along the North Wales coast but all were out of stock. I’m glad I did to as Sam the owner was spot on, talking me through the engine controls. I arrived when I was told it would be ready and PDI checked and it was waiting.

As the mariner 3.5hp outboard is not the most powerful of engines it will not suit every boat option. The key feature of this low powered outboard? Its low weight at 17kg gives it great portability for small boats. For a range of smaller boats or inflatables (SIB) it is a great budget option if buying new. New gives more peace of mind and a decent warranty. I soon got it running through its paces on a 3.3 metres 56kg SIB, eager beaver syndrome kicked in.

The inflatable boat was happy with 4 on board to potter around Ullswater with no hesitation. 2 adults and 2 children are pushed along consistently around 4 mph at quarter revs. Make sure you do its 10 hour run in period before pushing it too much though. At higher revs the boat will hit 6 mph with this weight but noise will become a factor. If its speed you are after then a larger model will be a much better option.

Having researched across multiple articles and boating forums it was clear that the SIB would never plane. However in practice this was definitely not the case, alone the front end popped up and it motored along. Bear in mind I emptied the boat of everything other than the engine. Moreover I thought to test it with a bit more weight in to see how it would go. I felt as it felt like it had more to give as it popped up so easily.

I got the boat setup at Nefyn beach on the Lynn Peninsula so on the sea this time. As extra weight my 11 year nephew was the guinea pig. The 3.5hp Mariner did manage to plane but it just took that bit longer to get going. Again no speed records were broke but it can and will plane regardless of what I had read. If you are thing of buying what I think is the best 3.5hp outboard then look no further. The 2.5hp Mariner is slightly cheaper but the same weight. So it makes sense to have that extra bit of power with the same portability if your budget allows.

At the higher end of the rev range you will only burn more fuel. With more weight it can’t plane, though its easy to find the happy medium of fuel and efficiency. With 4 onboard you will not get past displacement speeds so it really is pointless trying. The prop is plastic and comes complete with a spare sheer pin and some basic tools. Though not as efficient as Ali or Stainless due to flexing it helps keep the weight and cost of the engine down.

Why is the Mariner 3.5hp the best in my opinion? It comes down to brand reliability and cost. Japanese manufacturer Tohatsu makes the engine on behalf of Mariner as they do the much pricier Mercury models. All three are effectively the same engine, usually the Tohatsu’s come in cheapest, but it does not have the same dealer network backup hence I was willing to pay slightly more. I also prefer the more modern styling of the Mariner over the more bland looking Tohatsu.

As a first motor it is fine for pottering about on lakes and slow rivers. I have had 4 up fishing on the sea in a relatively sheltered bay, its fine as long as you keep an eye on the conditions. We even did a little tour over from Pystill Dock to Morfa Nefyn so its capable if used in the right sea conditions. One thing to bear in mind is it does not allow the attachment of an external fuel tank. You will have to fill it via Jerry can when out and about, it will happily potter on tick over for a couple of hours trolling. If you need to get back to shore quickly if the weather turns you will struggle so good planning is a must.

One thing to bear in mind is I used this motor multiple times on Ullswater and Derwent Water and only once on the sea. I decided I wanted to do a bit more fishing and exploring at sea and the 3.5hp Mariner would not be suitable for this. I traded the outboard in at Splash Marine and got a great deal on a 6hp Mariner. Its a far better motor and opens up more options with a quicker turn of speed but obviously this comes at increased cost and weight.

This size of outboard may be of better use on a smaller SIB such as a 2m – 3m range for better performance. As an auxillary outboard it will work well on larger solid bottom boats should you need it. Its price isn’t excessive and I would definitely choose a recognised brand with a solid history over a Chinese clone for peace of mind.

In terms of usability the 3.5hp Mariner has only forward and Neutral gears, to reverse the small engine needs to be swiveled 180 degrees. Its easy enough to spin so should not present any issue. One feature I do like is the visible oil check reservoir, quick and simple for ease of mind. It is a new engine but it is very easy to start with is CDI compression system. In terms of the best 3.5hp outboard the Mariner is is up at the top of the list for me.

Splash Marine can be found at:

Unit 11, The Bridgewater Centre, Robson Avenue, Trafford City, Manchester, M41 7TE. Tel: +44 (0) 161 748 4067

Large Displacement

  • Overhead design for direct and optimum power
  • Largest displacement in 3.5hp outboard class
  • 18% more displacement than direct competitors
  • Offers even more torque at same weight!

Long Tiller Handle With Twist Throttle

  • Easy to adjust steering friction
  • Durable design providing easy access for operator.
  • 32% less vibration than comparable Honda engines
  • 10% less vibration than comparable Yamaha engines
  • Improved customer comfort and control due to minimised vibration

1 Litre Integral Fuel Tank

  • External fuel shutoff valve. Can be laid on three sides safely.
  • Rugged, safe to transport and store.

Compact and Lightweight

  • 3.5hp offers more horsepower with the same weight of competitive 2.5hp.
  • Easy to carry and transport.

Quiet Running

  • One piece block design and underwater exhaust for incredibly quiet operation


Horsepower3.5hp (2.6kw)
Dry Weight17 kg
Revolutions Per Minute (RPM)5000-6000
Number Of Cylinders1
Trim Positions4
Induction System2-valve pushrod
Gear ShiftForward (F) – Neutral (N)
Gear Ratio2.15:1
Recommended Boat Transom Type381 mm (S) – 508 mm (L)
Fuel Tank Maximum Capacity0.95L
Fuel Tank TypeIntegrated
Fuel TypeGasoline
Fuel RequirementUnleaded 90 RON min.
Closed CoolingN/A
Engine Technology4 strokes

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