4 stroke V 2 Stroke outboard engines?

Seven Spades

Seven Spades

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I have one of the last Tohatsu 4HP 2-stroke engines and I hate it. I had it serviced at the end of last season and I am on the first day of my summer holiday and it won't start. I believe that the carb is probably booked up. In the past I had the 2.5hp version and it started first time every time.

I am pretty much at my wits end with this engine and I am thinking of switching it to a 4-stroke. Can anyone tell me of 4-strokes are more reliable than 2-strokes? During the course of a year we probably only use it on our summer holiday and in the Beaulieu so it has probably been run for fewer than 20 hours since we bought it.

Suggestions please.
 
Four strokes are more complex bits of machinery so potentially have more bits to go wrong but the concept is fairly well tried and tested.

Not without exception but likely to be heavier than their 2 stroke counterparts

Can only be carried and stored in limited orientations due to the lubricating oil sump.

If you are not fastidious in handling and storing fuel they are just as likely to suffer from carb problems although in that respect the use of straight gasoline with no added oil may be an advantage.

( My 6hp Evinrude 2 stroke is 30 years old I attempt to filter all fuel going into its tank and filter stored fuel without fail. Not yet had to touch its carb, even after it has stood idle for a couple of years at a time)

The plus points in favour of 4 strokes are that you no longer have to mix oil with the gasoline. There is no oily discharge from the exhaust and if you are a devout tree-hugger they are ( allegedly ) less polluting
 
Are 4-strokes less prone to problems with fuel clogging the carburetor than 2-strokes? I am at my wits end because I use my outboard so infrequently I really don't want to have to drain the tank after each use. As I say I never had this problem with my old engine. I am not sure if it is the new engine at fault because it might just be a coincidence I believe we now have a proportion of ethanol in our fuel and this is the main cause of the problem.
 
I think the tree huggery aspect is misguided. Most users do very limited mileage and use less than a couple of gallons a year. 10litres @ 1/50 = 200ml of oil. I've got a Seagull and a Honda 2.3. The Honda is easier to use but we'll see which is still going strong in another 40yrs.
 
All that Vic said. The reason your older engine didn't gum up so much is the change in the fuel you get from the pumps.
It will undoubtedly be the carb and you will save yourself a lot of expense by learning how to clean it properly. This does mean dismantling it, but it's just a few screws to loosen using (correct sized) screwdrivers. Removing the jets need a snug fitting screw driver or you may damage the soft metal of the slots. You may need a spanner to remove the carb from the engine. If you have an air line that is great for blowing through the carb passages. It is literally a 30 minute job, done well.
Fuel needs to be stored in opaque cans out of the light. It's daylight that effects fuel more than age.
If you only use it a for a brief period each year it's better to empty the fuel at the end of the season and put fresh in when you are about to use it.

It's a good idea to test the motor in a tank of water before you leave home. Wheely bins are good.


 
I have a Yamaha 2.5 4 stroke that I use rarely. Last time it sat for more then 2 years without use. I put some fuel in it and it ran after the second pull.
What I do at switch-off time, when I know I'm not using it afterwards in the direct future, I turn off the petrol valve and leave the engine running until it's out of fuel as a way to drain the carb. That keeps it from clogging up, I'd say. At the end of the season I drain the petrol from the internal tank.
In general the 4 strokes are more heavy but also more quit and less smelly compared to the 2 stroke stuff. The 4 strokers also run more smoothly unless you have a 2 cylinder 2-stroke version (there are a few small ones made by Evinrude if I recall correctly).
I agree with the tree-huggers argument. Any given SUV-car will cause more misery then a tiny 2 stroke so it's a moot point from that perspective. But the horrible 2-stroke smell is nice to get rid of.
 
Why does an SUV do more harm than an ordinary car?
My last two Grand Viatras did 36 mpg and my Jeep does 31 mpg. Plenty of cars are worse than that.
 
As everyone has said, 2 strokes are simplier and as long as they are run dry after every use and maintained well are excellent starters.

But, Im starting to get the feeling that the Tohatsu 4hp is the exception to the rule.

We had one of the last ones from 2006, maintained properly just like all my other outboards but if it didnt catch 1st pull it was a complete bugger to start. Didnt matter wether it was hot or cold, starting it required many, many pulls with different combinations of choke and throttle. It would always start eventually, but it was so much of a pain that I decided to get rid. I have noticed a few posts across different forums about starting problems with the 4/5hp Tohatsu.

By comparison all my other outboards start 1st or 2nd time.
 
Strange to read this as I also have one of the last 2 stroke Tohatsu 4hp (upgraded by dealer to 5hp) and it nearly always starts 2nd or 3rd pull (first if very recently run). The only time it does not start first time when warm is because I have never fully got to grips with the choke. Full choke for the first pull if completely cold, no choke if run in last 10 minutes but if it is still warm but not run for 15 minutes or so then I sometimes have to give it half choke which I do not think it should need. These are the times when it may need 3 or 4 pulls so I suspect if I KNEW how much choke to use it would start first or second time.

Do not treat it too preciously but always run the fuel out of the carb at the end of the season and run it in fresh water.

The 5hp is the most torquey outboard I have ever owned and will easily plane an Avon Rover 2.8 with two on board at just over half throttle. Keep meaning to take my phone with GPS to see what it's maximum speed is with just me on board but it is so fast that at times it can get a bit alarming ! I absolutely love it.

Edit: I also do not buy the polluting bit, a 1L bottle of oil will last for ages and considering that it must burn more than half that goes in the fuel the remainder is minute per use and certainly much, much less than the oil that goes down the sink when doing the washing up !
 
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My 3.5 Tohatsu has never managed to set the float level in the carb correctly. I have had it apart several times but it seems the needle valve operated by the float seeps a little so that it tends to flood but not to the extent that it drips petrol from the float chamber. Eventually I found that the way for it to run happily was to switch off the petrol as I approached beach/boat/pontoon so the level ran down a bit. It would then be fine tilted or left and would start happily without any choke. If I ran it dry to leave for some time on restarting I just briefly switch on the fuel tap and then off again. Once the engine started I could then just put the fuel tap on. It looks as if the rate of seep at the float valve is much less than the fuel usage so once started it will run indefinitely. Once I had sorted out a routine it has been absolutely fine ever since. This is not quiet the same as your problem but help you to understand the beast a little better!
 
catalac08 said:
My 3.5 Tohatsu has never managed to set the float level in the carb correctly. I have had it apart several times but it seems the needle valve operated by the float seeps a little so that it tends to flood but not to the extent that it drips petrol from the float chamber. Eventually I found that the way for it to run happily was to switch off the petrol as I approached beach/boat/pontoon so the level ran down a bit. It would then be fine tilted or left and would start happily without any choke. If I ran it dry to leave for some time on restarting I just briefly switch on the fuel tap and then off again. Once the engine started I could then just put the fuel tap on. It looks as if the rate of seep at the float valve is much less than the fuel usage so once started it will run indefinitely. Once I had sorted out a routine it has been absolutely fine ever since. This is not quiet the same as your problem but help you to understand the beast a little better!
Click to expand...

Is your 3.5 hp 2 or 4 stroke ?

Even though it is a different engine to mine I will try your techniques and see if they improve the warm starting and report back.

(reading this thread has reminded me I forgot to run the carb dry before we left the boat for a month without use grrrr)
 
ghostlymoron said:
I think the tree huggery aspect is misguided. Most users do very limited mileage and use less than a couple of gallons a year. 10litres @ 1/50 = 200ml of oil. I've got a Seagull and a Honda 2.3. The Honda is easier to use but we'll see which is still going strong in another 40yrs.
Click to expand...

The bunny-huggers are indeed misguided regarding modern SMALL two-strokes: I am now close to empty on my original one litre bottle of two-stroke oil for a 3.3 Mercury two-stroke that is now coming up to 9 years old. I'd have used significantly more oil if I'd done an oilchange every year on the current 4-stroke version. With two-strokes cleaning the carb thoroughly once a year is the key thing to do: if you do it when the engine gets put away for the winter it should start easily the next spring even on the old fuel.

I have a just-run-in Tohatsu 3.5 2/s in the cellar waiting for the Mercury to die, but no sign of it yet. Bought it new just before they stopped selling them.
 
If 2 Strokes are "banned" as outboards how come this Generator from Aldi is allowed?

https://www.aldi.co.uk/en/specialbu...st-product-detail-page/ps/p/800w-generator-1/

W28_PD_Sunday_New_UL6_53351fac3d.jpg
 
CoVianna said:
If 2 Strokes are "banned" as outboards how come this Generator from Aldi is allowed?

https://www.aldi.co.uk/en/specialbu...st-product-detail-page/ps/p/800w-generator-1/
Click to expand...

Simply because 2 strokes are not banned.

The demise of small two stroke marine engines ( inboards as well as outboards) is due to the emission regulations that became part of the Recreational craft Directive a few years ago

The generator is not a recreational craft although it could probably not be legally installed in recreational craft in the areas to which the RCD applies

The directive only applies to recreational craft .. not even to commercial craft.

Two stroke outboards which meet the emission standards are not affected either. Eg the fuel injected Mercury / Mariner Optimax engines and Evinrude E-tec engines
 
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