Petrol

Think_AgainThink_Again
edited December 2013 in General
Hi Just checking to see how the Forum works ! I have a fairly new Yamaha 9.9 4 Stroke which seems to play up from time to time especially after a trip of about 2 hours. Talking to Yamaha (BHG) he said that the new engines do not like the basic unleaded fuel that is for sale at the pumps and it is better to use the more expensive 95 octane. I did buy some super shell at the end of last season but did not have time to test properly. any comments please.

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    MeAndErMeAndEr
    ME-AND-ER
    Hi Bob hate to say it but that sounds like bull....
    have a good Christmas see you on the water next year.

    I have yet to get my sails off they are now in need of some restitching, they are now ten years old, my how the time flies..
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    CHATEAUCATCHATEAUCAT
    I have had no trouble using standard unleaded fuel for the past 5years although I needed to put some carb cleaner in once because I had left stale fuel in during winter layup.
    Merry Xmas to all hope to see some of you in the year 2014.

    Roy
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    ScubacatScubacat
    I try to use the "better" fuel for the boat, as it can stay in the tanks for rather longer than I care to admit, and I had heard that the bio-ethanol can be problematic, but that the "better" fuels have (lubricating?)additives. It is sometimes just noticeable that the boat engine runs better at the beginning of the season once the old (usually ~6 month old) fuel has run out and new is used. When I had a 2 stroke the difference was much more marked.
    I have not tried any cleaners or additives yet.
    This year we had rather less sailing than planned, so Cathy's car is still running OK on the "extra" boat fuel we bought in the summer.

    All the best
    Dagnall
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    [Deleted User][Deleted User]
    "This year we had rather less sailing than planned.."

    This is a disturbing trend. Are you addressing this issue for next year?

    I guess I can be flippant, living in a place with year round sailing weather. Sorry.
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    ScubacatScubacat
    No problem!, hopefully better sailing in 2014!
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    Think_AgainThink_Again
    Since starting this discussion on Petrol, we still seemed to have had problem with the engine, at the time a fairly new Yamaha 9.9 4 stroke, the sequal being that although being meticulas with new fueltanks fuel filters and a high grade fuel, the problem was in the fuel lines, we had developed an air leak, which over a period of time would effect the amount of fuel getting to the carburettor, as we only found this out on our last trip of 2014 we are hoping that it wont be a problem in 2015, Lets hope its as good a season as this year..Best wishes Bob & Ann Think Again
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    ScubacatScubacat
    Very interesting! Looks like another thing to check very carefully at the end of the season. Presumably if the leak in the line is somewhere above the fuel tank level, then it can let in air, but you would not get a "drip" of fuel to tell you you had a problem. 

    FYI, I changed Scubacat's prop this year to a 9.25 by 10 inch four blade. The result is much improved fuel consumption, with the engine running at lower revs for reasonable speeds, topping out at about 3800-4000 revs. 
    (I have the Yamaha 20 which is the 9.9 with a bigger carburetor and supposedly more HP when revved  to 5500).
      
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    Think_AgainThink_Again
    Hi Dagnal, I wonder what differance the new prop made to the fuel consumption on the 20 HP. I can get just over a litre an hour at 4000 revs on the 9.9. Bob
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    ScubacatScubacat
    I found the log book at last (long story) and have done my sums. 
    With my 20 horse long shaft Yamaha, and the 4 blade 9.25 x10 prop, we used on average 2.71 litres per hour over a total of 63 hrs motoring. Mostly "pushing to get somewhere" rather than slow pottering into harbours etc. When I bothered to record rpm, it was mostly 3200 to 3600.
    Average chart distance based speed was 5.7 kts, which is higher than I expected. 
    Certainly the new prop gave a more relaxed motor sailing experience when we motor sailed in lower winds.
    I expect if I ran slower I could decrease the consumption, but we usually have the engine on because we want to get somewhere!.  Dagnall

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