Old Yamaha 2 Stroke Outboards?

[Tim Good]

I’m looking for a 6-8hp 2 Stroke Yamaha to replace my 3.5hp mercury 4 stroke.

I’m considering Yamaha pretty much because I see them a lot while cruising abroad and everyone claims they’re the best of all 2 strokes and easy to maintain. Reliable and light.

Anyway there are various online for sale but is there one type I should look out for?

There’s an old 8Hp 667 near me and a really old 6hp. See pics. Although they run are these likely to be more of a liability than a long term reliable investment?

 

[RJJ]

We have a slightly more recent 6hp 2str, came with the boat.

Goes like shit of a shovel, I am unsure the labelling is accurate!

No problems so far except when the carb clogged up and I had to pay to get it cleaned. Now I know how....

The wee stream needs poking out almost every time we use it.

 

[Refueler]

Yamaha .. Tohatsu ... Mariner .... all good and based on similar engines.

The only old Yammies I would steer clear of are the small air-cooled jobs. I had a couple of them and they were excellent runners - but being aircooled - they needed the TA 2str oil ... and were a bit noisier ... and if got hot - reluctant to start quite often.

 

[Refueler]

We have a slightly more recent 6hp 2str, came with the boat.

Goes like shit of a shovel, I am unsure the labelling is accurate!

No problems so far except when the carb clogged up and I had to pay to get it cleaned. Now I know how....

The wee stream needs poking out almost every time we use it.

I don't know how you stop your outboard ... but if you stop it by the 'button' and then leave it for days ... the petrol content in carb can evaporate off and you get left with 2T oil and gum. Makes starting extremely difficult.

All my engines .. Mariner .. Johnson ... Evinrude ... Veta ... Neptune etc. - I always religiously pull the fuel line off and let it run dry to stop if I am leaving engine for longer than a few hours. Next time I use - pump fuel in ... pull cord 2 or 3 times and away she goes.

Some people say not to do this .. claiming engines with Walbro type carbs need the diaphragms to stay wet. Fair enough ... but I have 4 petrol strimmers ... various outboards ... model airplanes with Walbro type carbs and all are fine with above.

 

[RichardS]

I don't know how you stop your outboard ... but if you stop it by the 'button' and then leave it for days ... the petrol content in carb can evaporate off and you get left with 2T oil and gum. Makes starting extremely difficult.

All my engines .. Mariner .. Johnson ... Evinrude ... Veta ... Neptune etc. - I always religiously pull the fuel line off and let it run dry to stop if I am leaving engine for longer than a few hours. Next time I use - pump fuel in ... pull cord 2 or 3 times and away she goes.

Some people say not to do this .. claiming engines with Walbro type carbs need the diaphragms to stay wet. Fair enough ... but I have 4 petrol strimmers ... various outboards ... model airplanes with Walbro type carbs and all are fine with above.

Every time anyone on here suggests running a 2T with the fuel turned off until it stops, someone mistakenly says that if you do that the mixture gets weaker and weaker until the engine seizes through lack of lubrication.

I'm not familiar with outboard engines that use diaphragm carbs but, certainly with float chamber carbs, once the engine stops there is at least 25% of the fuel left in the chamber so, assuming that outboard diaphragm carbs use a similar chamber design, then the diaphragm certainly won't be running dry.

Richard

 

[Refueler]

Every time anyone on here suggests running a 2T with the fuel turned off until it stops, someone mistakenly says that if you do that the mixture gets weaker and weaker until the engine seizes through lack of lubrication.

I'm not familiar with outboard engines that use diaphragm carbs but, certainly with float chamber carbs, once the engine stops there is at least 25% of the fuel left in the chamber so, assuming that outboard diaphragm carbs use a similar chamber design, then the diaphragm certainly won't be running dry.

Richard

Thank you .... as you say the chamber does not actually go dry. But its low enough to not then have jets etc clogged by oil left after evaporation of the gasoline part.

The engine stops due to lack of sufficient fuel in the fuel/air mix. It does not get weaker and ever weaker as some imply. Yes it must weaken but the reduction in fuel/air only needs to be a small amount to cause engine to stop.

On the subject of lubrication - anyone remember the days of 20:1 then 50:1 changing to 100:1 ? I can remember people claiming engines would seize ... but they didn't. I admit that manufacturers jumped onto the 100:1 a bit quick to satisfy the 'Greenies' and not long after some backed off back to 50:1. But basically little damage had occurred ... as many of those engines that ran 100:1 were barely modified from their 50:1 sisters.

Memories flooding back ... 20:1 .. 25:1 Seagulls !! The unmistakable putter of the old Featherweight sounding across the harbour ... reckon if I dig deep enough into a locker - I will find a Seagull starting cord !

 

[RichardS]

Thank you .... as you say the chamber does not actually go dry. But its low enough to not then have jets etc clogged by oil left after evaporation of the gasoline part.

The engine stops due to lack of sufficient fuel in the fuel/air mix. It does not get weaker and ever weaker as some imply. Yes it must weaken but the reduction in fuel/air only needs to be a small amount to cause engine to stop.

On the subject of lubrication - anyone remember the days of 20:1 then 50:1 changing to 100:1 ? I can remember people claiming engines would seize ... but they didn't. I admit that manufacturers jumped onto the 100:1 a bit quick to satisfy the 'Greenies' and not long after some backed off back to 50:1. But basically little damage had occurred ... as many of those engines that ran 100:1 were barely modified from their 50:1 sisters.

Memories flooding back ... 20:1 .. 25:1 Seagulls !! The unmistakable putter of the old Featherweight sounding across the harbour ... reckon if I dig deep enough into a locker - I will find a Seagull starting cord !

My first motorbike, which I bought a year or so before I was 16 and old enough to ride it on the road so that I could strip it down and rebuild it, used 25:1 but we didn't use posh 2T oils in those days but just chucked in some 20W-50 engine oil so they were definitely smoky and unburnt oil used to drip out of the end of the exhausts.

We were always told that adding some extra oil for improved lubrication was more likely to seize the engine because the fuel/air mixture would then be weaker so the engine would run hotter and therefore be more likely to seize. I'm not sure that I ever believed that because those old two strokes had so much piston slap that seizing seemed to be highly unlikely either way.

Richard

 

[Refueler]

My first motorbike, which I bought a year or so before I was 16 and old enough to ride it on the road so that I could strip it down and rebuild it, used 25:1 but we didn't use posh 2T oils in those days but just chucked in some 20W-50 engine oil so they were definitely smoky and unburnt oil used to drip out of the end of the exhausts.

We were always told that adding some extra oil for improved lubrication was more likely to seize the engine because the fuel/air mixture would then be weaker so the engine would run hotter and therefore be more likely to seize. I'm not sure that I ever believed that because those old two strokes had so much piston slap that seizing seemed to be highly unlikely either way.

Richard

Love it !!

My brothers who rode Lambo's before me - always gave a shot of Redex in the tank each fill up ....

Me ? I was always too skint to afford Redex !!

Memories ... setting the petrol - oil ratio on the pump before winding the handle to dispense to tank !!

 

[duncan99210]

I’ve got a 4hp 2 stroke Yamaha for the Hurley 18. Bought it off eBay for £175, paid to have the carb cleaned through (£30!) and it’s not missed a beat since. Starts second to third pull and produces enough power for the job. Also got a Mercury 2.5 as the dinghy motor. No real problems with it at all.
As with all 2 strokes, it pays to keep the fuel fresh and the carb empty if you’re not going to use it for a bit. Have fun.

 

[Refueler]

it pays to keep the fuel fresh

I always smile when I read this ... no disrespect intended.

All Gasoline / light distillates when blended need careful storage. The three main items are : Light, Heat and Oxygen.

All three have a detrimental effect on particularly gasoline. When we hold samples of traded gasoline - we have to keep in dark, cool place and sealed. The bottles are dark to limit light effects when being transported. Bottles and cans have a press in seal before cap screwed on.
Those samples are stored for minimum 90 days ... often much longer.

OK - what about my outboards and my fuel ? I use metal Gerry Cans - what I call Land Rover Cans to store my gasoline in. I mix what is needed with 2t and put into typical 4 ltr plastic cans for garden machinery - or direct to outboard fuel tank.

After use - I close the vent on the O/Bd tank. That tank can stand all winter in a cool dark corner and in spring - I top up with fresh mix and I never have any trouble with it.

Just to illustrate how tolerant fuel can be. My Soviet motorboat while I was away on travels suffered flooding with engine half submerged and the tank underwater.

Engine to pal for service .. tank emptied to clear containers ... and let water settle out, Syphon of gasoline to more clear containers, leaving a fewmm + water behind.
Stand for a day in dark cool place and then check for water again. Decant and refill tank.
No problems at all.

 

[DownWest]

I have a Yam 3.5 2T. It starts easily, even after a winter with old fuel. No impellor to worry about or cooling passages to clog. BUT, it is noisy, so for use when the wind don't blow.
Refueller, your memory is at fault, I still have a Seagull that requires 10:1 ! But I need to try it on the bio-degradable oil to do my bit for the planet.. Less guilt about the sheen it leaves behind on the water..

 

[Refueler]

I have a Yam 3.5 2T. It starts easily, even after a winter with old fuel. No impellor to worry about or cooling passages to clog. BUT, it is noisy, so for use when the wind don't blow.
Refueller, your memory is at fault, I still have a Seagull that requires 10:1 ! But I need to try it on the bio-degradable oil to do my bit for the planet.. Less guilt about the sheen it leaves behind on the water..

Was it 10:1 ... so long ago ...

I know they did re-jet in later years to 25:1 .....

Sheen ... I cannot help but smile ... anyone who's had a Seagull can attest to that ... not only when running - but when refilling the tank .. spills ... and the drip drip drip from knackered cork washer in the on off tap !

Memories ..... trying to remember to warn any others going with you in tender .... heads down while I pull the cord !! I can remember catching a rather nice looking young lass one time with the cord end ...

 

[DownWest]

Was it 10:1 ... so long ago ...

I know they did re-jet in later years to 25:1 .....

Sheen ... I cannot help but smile ... anyone who's had a Seagull can attest to that ... not only when running - but when refilling the tank .. spills ... and the drip drip drip from knackered cork washer in the on off tap !

Memories ..... trying to remember to warn any others going with you in tender .... heads down while I pull the cord !! I can remember catching a rather nice looking young lass one time with the cord end ...

Yep, you could rejet to 25:1, but only if you had the right carb. I don't.

Horrible case in the US, young girl caught her long hair on the flywheel, others rushed aft to help. Stern submerged with the extra weight and it sunk. The girl drowned as still caught on the engine, the rest got off.

 

[Refueler]

Yep, you could rejet to 25:1, but only if you had the right carb. I don't.

Horrible case in the US, young girl caught her long hair on the flywheel, others rushed aft to help. Stern submerged with the extra weight and it sunk. The girl drowned as still caught on the engine, the rest got off.

Terrible ..... so sad.

 

[coveman]

Back to the original question - I have a 8hp 2 stroke Yamaha - excellent engine and starts first time. Service it regularly and it will do you well, but it is worth waiting for a good one to come up for sale which is rare and they usually command a good price. Although they say they will run at 100:1 most dealers now recommend 50:1 especially as the age of these engines means they will have some wear. As has been said the small "pee" hole does block but a fine piece of wire usually cures this, in my experience.
I spoke to one of the mechanics at Robin Curnow (Yamaha dealers in Falmouth) and his advice was to keep it as long as possible, as the equivalent power from a 4 stroke means an engine twice the weight!
Good luck with your search

 

[Seajet]

The Yamaha 4hp two stroke is very good, just check the gearshift moves freely as the plastic can swell and stick - easily solved and I drilled an oiling point to prevent it happening again.

Otherwise pretty bullet proof and so much lighter than a 4 stroke !

 

[greeny]

Otherwise pretty bullet proof and so much lighter than a 4 stroke !

And a 5hp 2 stroke always seems to be more powerful and faster than a 5hp 4 stroke. I know that 5hp is 5hp regardless of what is delivering it but they do seem to be appreciably faster.

 

[pagoda]

Always lighter, mechanically simpler, easy to work on.... what's not to like about small 2T engines.

 

[Graham376]

Always lighter, mechanically simpler, easy to work on.... what's not to like about small 2T engines.

Agree. If you can do the work yourself, single cylinder 2 strokes are very simple and worth repairing for far less cost than buying a new 4 stroke. Twins can be more problematic if the centre crankshaft seal or main bearings are knackered as it needs either a new assembly or a specialist to separate the two halves of the crankshaft, fit the new parts and reassemble. Unfortunately, not many specialists around but some in the the motor bike trade have the skill.

 

[Refueler]

Popularity of 2 strokes ..... less are for sale - not because of them being binned or not working ... but because people don't want to sell !
Those that do come up for sale - some are just daft prices asked ...