2 stroke or 4 stroke Outboard

Submitted: Saturday, Jan 12, 2008 at 23:20


We have a 3.7 SeaJay Nomad aluminium tinny, As we will be travelling around oz this year and are due to update our outboard, which we will be storing in the rear of our vehicle while travelling we were wondering if we could get the Pros and Cons about whether to replace our motor with either a 15HP 2 Stroke or 15HP 4 Stroke. At this point we are thinking Yamaha???? any suggestions.
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AnswerID: 281290   Submitted: Saturday, Jan 12, 2008 at 23:47

Member - bushfix replied:


you can't go wrong with Yamaha. They are the best IMHO. At 15HP and the travelling you plan, 2 stroke would be the go. They are lighter than a 4 and although not as quiet, are the most oft found in that class. Parts would readily available but you would already have a very reliable donk and if reselling, would fetch a good price.

A very worthwhile alternative would be the Tohatsu. A cheaper motor but very well built and reliable. Either way, as long you keep the fluid levels up, a regularly serviced motor should take care of the rest when on the run.
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FollowupID: 545675   Submitted: Sunday, Jan 13, 2008 at 07:24

Member - Brian H (QLD) posted:

The Tohatsu is a great motor not sure of the weight difference (if any) but it is an 18HP and goes like a scalded cat. My mate has one I have a 15hp Jono I only got my Jono as I was given a FANTASTIC deal. I now which I got the Tohatsu. Its also very good fuel wise.

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FollowupID: 545678   Submitted: Sunday, Jan 13, 2008 at 07:54

Member - andrew B (Kununurra) posted:

I could be wrong (often am!), but I think the tohatsu is also prop hp not flywheel, explaining the scalded cat performance.
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FollowupID: 545711   Submitted: Sunday, Jan 13, 2008 at 12:03

madfisher posted:

All motors have been rated at the prop for at lest the last ten years.
Tohatsus are a very reliable motor, but not designed for slow trolling. Yamaha or any other motor will be better in this regard.
I would go 2 stroke because they are lighter, and I believe you can only lay a 4 stroke down on one side
Cheers Pete
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AnswerID: 281301   Submitted: Sunday, Jan 13, 2008 at 01:21

Mainey (wa) replied:

Coolit, I also suggest the 2 stroke for same reasons.

The Tohatsu I would definately not consider, reason being, the 'commercial' Fishing and Cray fleet owners up the coast don't use them on their tender boats, for good reasons.

In the larger HP, 2 stroke range, I believe Evinrude is a clear winner, but I'm not aware if they make a 15hp outboard.
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AnswerID: 281307   Submitted: Sunday, Jan 13, 2008 at 08:05

Member - andrew B (Kununurra) replied:

Gday coolit

As above have said, in that size I would go a 2 stroke, mainly for the weight. In a small tinny you probably won't be travelling distances that fuel economy is a problem. Noise is easy to deal with - ear plugs. I always wear them even with the 4 stroke, the wind noise at speed drowns out the engine noise in my case anyway.

Cheers Andrew
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AnswerID: 281316   Submitted: Sunday, Jan 13, 2008 at 09:00

happytravelers replied:

I've had a 2 stroke Tohatsu badged as a Mercury for five years, used regulary at weekends without any problems. Apart from the noise they're a very good motor.
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AnswerID: 281317   Submitted: Sunday, Jan 13, 2008 at 09:03

Member - Norm C (QLD) replied:

Coolit, as others have said, 2 stroke is the way to go.

I used to have a Mercury 15 HP. Excellent motor and the lightest in its class @ 35 KG. From memory the Yamaha is 36 KG so not much difference.

I recently upgraded my boat from 3.5 to 3.75 and wanted to get a 20HP to give more grunt for longer fishing trips we do up in the Gulf. I considered a 4 stroke and spoke to the local Honda dealer. When I described the intended use (for roof topper), he said:

'Mate, I'd love to sell you a Honda, but I'd be doing the wrong thing. You want a 2 stroke. Apart from the weight and rapid power response, a 4 stroke doesn't like being tipped on it's side to carry. You run the risk of the engine oil leaking out inside the motor and causing you grief. For a 20 HP 2 stroke, I wouldn't get anything other than a Yamaha'.

We got a Yamaha and it is terrific, though a 20 HP. I have no personal experience with the Yamaha 15HP, but have no doubt it is a good motor.

So from my perspective, the Mercury and Yamaha are both good motors. If you already have a preference for the Yamaha, I see no reason to change.

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AnswerID: 281322   Submitted: Sunday, Jan 13, 2008 at 09:45

age replied:


I recommend the 4 stroke Yammy. The 2 stroke is a great motor, but the 4 is superb. Weight wise, there is 9kg difference between the 2 and 4 motors at 15hp - Consider that for the 2 stoke you will be also carting around a 4L (4Kg) bottle of 2 stroke oil, the weight gap narrows to 5kg. The 4 stroke is a little more economical on the fuel as well. Resale value for the 4 stroke kills the 2.

Re Hp ratings as mentioned above - Since 1986 all major outboard brands state Hp at the prop not the crank.

Nothing wrong with the Tohatsu motors for bang for buck - they are a great reliable motor, but get your Tohatsu price and squeeze your Yammy dealer - they will often go close to matching price.


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AnswerID: 281334   Submitted: Sunday, Jan 13, 2008 at 10:38

Sand Man (SA) replied:

I also recommend a 2 stroke motor.

The 3.7 SeaJay would have a maximum HP rating, but a 15hp should suit this craft.

To my knowledge, the Mercury and Mariner outboards are the same, just rebadged.

For the "occasional" use you would be doing with the boat, economy is not a factor and the 2 stroke will have more low down grunt.

I own both a 4hp 4-stroke (Mariner) and a 15hp Mercury for use on my 3.4 metre tinnie and the 15hp twin cylinder engine is much smoother than the single cylinder motor. The singles tend to vibrate at all throttle settings whereas the twins, probably due to the opposed cylinder operation reduce any vibrations to a negligible amount.

That's my experience anyway.


I'm diagonally parked in a parallel Universe!
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AnswerID: 281365   Submitted: Sunday, Jan 13, 2008 at 12:45

_gmd_pps replied:

what a nobrainer .. 4 stroke all the way ..
even my little 2.5 Suzuki on my small tender is a 4 stroke.
starts always, never glogges up with old fuel, fuel does not need treatment, no oil, doesn't stink as bad as a 2 stroke ...
I have thrown out all 2stroke gear, that includes lawn mower, whipper snipper, chain saw, pressure cleaner and transfer pump.

good luck
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AnswerID: 281380   Submitted: Sunday, Jan 13, 2008 at 14:55

Member - Norm C (QLD) replied:

Coolit, this link discusses the pros and cons of 2 stroke v 4 stroke. There are pros and cons of both. A matter of selecting the motor that best fits your particular needs. For me it is currently 2 stroke. For you and others, it might be different.

Hope it helps:
4 stroke v 2 stroke comparison
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AnswerID: 281455   Submitted: Sunday, Jan 13, 2008 at 20:44

blackmax11 replied:

As most others have said, 2 stroke is the most sensible for your application. Not only lighter than a four stroke but a much better torque curve than any 4 stroke. This means better performance, quicker on the plane, keeps on the plane at lower speed and better load carrying.
Mercury and Mariner have 2 models each in the 15hp 2 stroke range. There is a USA built model which has the best features and benifits of any 15hp on the market. It even has a manual trim system, no having to stop and change tilt pins to get the boat / engine right for different loads. Gear change and throttle all in the tiller and lots more. Its my engine of choice V's all brands and its the lightest 15hp on the market.
The other 15hp is called a 15hp Super as it is 18hp in the Tohatsu range. Mercury own 50% of Tohatsu, hence the arrangement.
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AnswerID: 282151   Submitted: Thursday, Jan 17, 2008 at 21:28

Bros 1 replied:

Tohatsu is the go. They are basic but good. Take my 18 to Bathurst Bay in a box and starts second pull. Scalded cat runs second. LOL. Just started it up at home in early Dec. and still went second pull after 12 months.
Work is the curse of the down and out bludger.
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