Thanks Thanks:  2
Likes Likes:  6
Page 1 of 2 12 LastLast
Results 1 to 10 of 14
  1. #1
    Join Date
    Apr 2013
    Location
    Ireland
    Posts
    187

    Default Yamaha 5 ho outboard 2 stroke

    Hello,
    I was heading out on the lake with a friend and we brought our 5 hp Yamaha 2 stroke outboard. We set out on the lake and it started bogging down on full throttle and then cut off and took several pulls to get it going again and then it would run for a bit before happening again. Sometimes it would bog down and get up to power again but it kept doing that in a cycle of up and down with the power output. It only did this at full throttle and was fine st half. We went back to shore and stripped the carburettor and cleaned it finding some dirt and changed the spark plugs. Went out again to give a few runs close to the shore to see if it was fixed and it did it twice again but then suddenly seemed to have cleared twelfths and it was running fine and didnít cut out after taking multiple short runs close to the point we left from. Iím thinking it may have been some water in the fuel but donít know if this could happen again. On the bright side we werenít miles up the lake when it happened as itíd be a long roe back into the wind. By the time we were investigating it we ran out of time to fish. As they say things happen.
    I love fly fishing and hold it as a major part of my life!

    Tight Lines,
    flyfisher147

  2. #2
    Join Date
    May 2006
    Location
    Central Scotland
    Posts
    29,946

    Default Re: Yamaha 5 ho outboard 2 stroke

    I ''Would'' have suggested that the inpeller was not working properly and the engine was overheating.but as it cleared up this is probably not the problem.Sorry.

    Jim
    The Fishermans Friend is the Flirty Fly,Fickle Food for Fleeting Fish.

  3. #3

    Default Re: Yamaha 5 ho outboard 2 stroke

    Sounds simple, I know - but did you open the air vent on the fuel tank fully? It is a common oversight. If you did then it sounds a bit like fuel starvation, or over-fuelling and without looking at the plugs I can't say which.

    Just go through and do a proper service before next time:
    Change the air cleaner - it is far more important than the fuel filter, but gets overlooked very frequently. 100cc motor running at 5000rpm (easy maths, but about right for yours) uses 2 litres of fuel per hour, at a fuel ratio of about 13:1, it is probably about 12.8, but 13 will do for fag packet maths....

    So your fuel filter has to deal with 2 litres, whilst your air filter is sorting out 26 litres of air in the same time scale. Yet people ask for the fuel filter to be done, but don't bother with the air filter - to try and save £10!

    New plugs - but keep the old ones and put them over a brass wire wheel to clean them and keep them in the spares/tool kit. Check the colour of them when you take them out, it tells you an aweful lot about how the engine is running. I would bet a £1 to 1p that yours are black and oily, indicating you are running very rich, which is how it sounds - the engine was fouling the plugs, then every now and then burning them off and running a bit, then fouling them again.
    If they are creamy with white spots, BE VERY CAREFUL, you are on the verge of burning a hole in your piston because you are running way too lean, but then it would be revving like hell and possibly 'hunting', where the revs rise and fall in a rythmic fashion without altering the throttle position.
    The plugs should be a nice coffee colour, coffee with milk, not back coffee! And with no white spots - they are heat spots.
    I suggest you take the plugs out and look at them now, before you do anything to the motor. Then you can diagnose what else needs looking at.
    Ignition timing and strength - is the coil leaking a bit and so only giving intermittent sparks? Just because it is CDi doesn't mean it can't go wrong or out of synch.
    Fuel/water filter - yes this needs emptying and the glass bowl cleaning - or if you have one of those little plastic, in-line filters then change it, every 2 years if it sits doing nothing for half the time, more often if used regularly, at least once a year.
    Use good 2-stroke oil, ash free marine oil is best - it doesn't leave any residue on the water..... you wouldn't want to pollute your fishing water for the price of a dram now would you? You can use strimmer/chain saw oil happily, but it is much dirtier through the exhaust and one reason so many waters refuse the use of conventional 2-strokes and why they were made illegal to sell new. The E-Tech uses entirely different technology and whilst it has a power stroke every crank rev, it is high pressure injection and uses less lubricating oil than a 4-stroke over a season... another conversation.

    Water pump impellor is pretty vital to happy boating too. If you have a strong tell-tale, then all is good, but remove it for laying up so iit doesn't take on a 'set' - if it is intact but old and the vanes have set in a curve, you can restore it by putting it in a pan of boiling water for a few minutes - put a cloth in the pan and the impellor on top of the cloth to protect it from direct heat. If the balled ends of the vanes have any cracks or nicks - chuck it and buy a new one. They are about to break off and, at best, leave you with an inefficient water pump not cooling properly - at worst some of the broken impellor vane will block the waterways and cause overheating through restricted water flow. neither is desireable!

    Gearbox oil change - small bowl below the leg, undo the bottom screw on the leg, then undo the top one and let the oil fall out - it should be darkened but clear. If there is any milkiness or it is a silvery grey colour your gearbox is leaking water and the seals need replacing for the milky oil, check the gears if it is silvery grey, because the gear teeth are flaking - that silvery greyness is the metal from your gear teeth, if it is very bad the oil will be like runny, grey toothpaste!

    Lube the rubber bush that the prop runs on - red rubber grease, just the merest smear. DO NOT USE WD40 or anything like that, it will cause your rubber bush to harden and eventually crack. If it is a very old Yam, it will still be using the shear pin system - replace the shear pin every season, they take a shock loading when you put her into gear, and every time you hit a rock, even if it doesn't shear, it weakens. Carry TWO spares in your spares kit, because if you have to replace one while out - if you only carry one, you now have no spare!

    Post back what state your plugs are in and I will help again if I can.

  4. #4
    Join Date
    Aug 2016
    Location
    Moray, Scotland
    Posts
    1,341

    Default Re: Yamaha 5 ho outboard 2 stroke

    I haven't fished from a boat yet but I am surprised that 2 stroke engines are still in use/allowed.

    Fantastic engines for motorcycles now sadly killed off (probably rightly so) by emission regulations.
    Only when the last tree has been cut down, the last fish caught and the last river poisoned, will we realise, we cannot eat money.

  5. #5
    Join Date
    Nov 2010
    Location
    Highlands
    Posts
    5,441

    Default Re: Yamaha 5 ho outboard 2 stroke

    using old mixture doesn't help a 2 stroke, the petrol evaporates leaving you with an oil rich mixture,makes difficult starting , easker1

  6. #6
    Join Date
    May 2006
    Location
    Central Scotland
    Posts
    29,946

    Default Re: Yamaha 5 ho outboard 2 stroke

    Quote Originally Posted by morayfisher View Post
    I haven't fished from a boat yet but I am surprised that 2 stroke engines are still in use/allowed.

    Fantastic engines for motorcycles now sadly killed off (probably rightly so) by emission regulations.
    This is not true..A good condition 2 stroke O/B using marine grade 2stroke oil will be as clean as a 4 stroke O/B. and if you move to a fuel injected 2 stroke(available now) they can have less emissions than a 4 stroke.What are they using to lubricate the Gas O/B that water boards are now demanding.Must be Oil.

    Jim

    PS having grown up with 10/1 mix O/B engines.I can see where regulators are coming from.but they are way behind the tech that is now running.
    Last edited by 3lbgrayling; 15-07-2019 at 10:59 PM.
    The Fishermans Friend is the Flirty Fly,Fickle Food for Fleeting Fish.

  7. #7

    Default Re: Yamaha 5 ho outboard 2 stroke

    Quote Originally Posted by morayfisher View Post
    I haven't fished from a boat yet but I am surprised that 2 stroke engines are still in use/allowed.

    Fantastic engines for motorcycles now sadly killed off (probably rightly so) by emission regulations.
    On any managed waters (authority waters) they are not. It is the wild waters where they can be used. Other than Etec they are no longer sold new, throughout the EU. Existing 2-strokes can be bought used and are legal to use on open waters, but I expect this situation to change soon, with the Canal & River Trust being held to account for their waters. The trouble is, Scotland has different laws, rules and regulations to England and Wales, so the situation could be different up there, but not on the new sales front.

  8. #8

    Default Re: Yamaha 5 ho outboard 2 stroke

    Quote Originally Posted by 3lbgrayling View Post
    This is not true..A good condition 2 stroke O/B using marine grade 2stroke oil will be as clean as a 4 stroke O/B. and if you move to a fuel injected 2 stroke(available now) they can have less emissions than a 4 stroke.What are they using to lubricate the Gas O/B that water boards are now demanding.Must be Oil.

    Jim

    PS having grown up with 10/1 mix O/B engines.I can see where regulators are coming from.but they are way behind the tech that is now running.
    It is interesting that Austrian lakes have been Electric only since the early 70s, I seem to remember 1972 for some reason, but that isn't gospel, UNLESS you had a commercial 'grandfather rights', so the passenger ferries, some are solar/plugin electric, but others are diesel. The local commercial fishermen can use their little outboards and the boating trade places, such as Frauscher, can use the lake for 'testing and demos' for their monsterous powerboats - twin 375hp jobbies. The rest of the boating public have to sail, row or use electric, the Lehr butane gas outboards are not popular because they are noisy, vibrate like hell and the gas bottles take up half the boat, but they are legal. Frauscher also build electric boats, they have done since the 1970s, in fact their first one was 1969. Switzerland is less strict than Austria!

  9. #9
    Join Date
    Aug 2016
    Location
    Moray, Scotland
    Posts
    1,341

    Default Re: Yamaha 5 ho outboard 2 stroke

    Quote Originally Posted by 3lbgrayling View Post
    This is not true..A good condition 2 stroke O/B using marine grade 2stroke oil will be as clean as a 4 stroke O/B. and if you move to a fuel injected 2 stroke(available now) they can have less emissions than a 4 stroke.What are they using to lubricate the Gas O/B that water boards are now demanding.Must be Oil.

    Jim

    PS having grown up with 10/1 mix O/B engines.I can see where regulators are coming from.but they are way behind the tech that is now running.
    I'm not an expert but it's hard to see how any 2 stroke engine can be as clean as a 4 stroke.
    Even KTMs recent developments in direct injection of fuel into the transfer port still have oil injected to lubricate the bottom end and the bore which then must end up in the combustion chamber.
    As far as I know these engines which have much lower fuel consumption than previous 2 stroke are still only on sale in off road bikes.
    Presumably, if they could pass current euro regs, KTM would have a road bike on sale now to cater for the generation that would buy one instantly who wish they had an RD250/350LC in the garage.
    Only when the last tree has been cut down, the last fish caught and the last river poisoned, will we realise, we cannot eat money.

  10. #10

    Default Re: Yamaha 5 ho outboard 2 stroke

    Quote Originally Posted by morayfisher View Post
    I'm not an expert but it's hard to see how any 2 stroke engine can be as clean as a 4 stroke.
    Even KTMs recent developments in direct injection of fuel into the transfer port still have oil injected to lubricate the bottom end and the bore which then must end up in the combustion chamber.
    As far as I know these engines which have much lower fuel consumption than previous 2 stroke are still only on sale in off road bikes.
    Presumably, if they could pass current euro regs, KTM would have a road bike on sale now to cater for the generation that would buy one instantly who wish they had an RD250/350LC in the garage.
    Everyone conveniently forgets the gallon of oil sitting in the sump of a 4-stroke, that requires disposal at regular intervals..... and a 2-stroke gets the correct lubrication from the moment you press the starter. 4-strokes require to warm up to get full lubrication - how many boaters allow their engine to idle for 3 or 4 minutes before heading out? Not many, I can tell you. The result is that 10 year old 4-strokes burn oil, but that oil is not designed to be burned, and where does an outboard exhaust this burned oil? Straight out through the hub of the prop, and partly through the leg just above the waterline! But that doesn't count, because tests are only conducted on brand new engines - and the engine used for emissions tests is shelved and never run again, in case the test has to be re-run. I wonder what the outcome would be if ther authorities required all engines to be tested for emissions every year.... the results would be interesting, not a single motor would achieve the same result as that test engine!

Page 1 of 2 12 LastLast

Similar Threads

  1. Yamaha 15hp 2 stroke, air fuel mix screw = dirty plugs ?
    By stylie in forum Boat Fishing, Kayaking and Float Tubing
    Replies: 10
    Last Post: 14-02-2015, 12:48 PM
  2. Mariner or Yamaha 2 stroke
    By 3lbgrayling in forum Boat Fishing, Kayaking and Float Tubing
    Replies: 5
    Last Post: 18-10-2012, 07:17 AM
  3. Mariner or yamaha 2 stroke o/board
    By 3lbgrayling in forum Wanted/Swap Classifieds
    Replies: 0
    Last Post: 05-09-2012, 01:07 PM
  4. Yamaha 9.9 4 stroke engines
    By Jungle Bunny in forum General Fly Fishing Discussion
    Replies: 4
    Last Post: 03-06-2011, 11:17 AM
  5. yamaha electric outboard
    By sooty in forum Tackle Talk
    Replies: 0
    Last Post: 07-04-2010, 09:51 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •