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DISASTER 99 mariner 40 hp motor rough on test drive

Discussion in 'Boats and Motors' started by bassteaser1, Mar 23, 2005.

  1. bassteaser1

    bassteaser1 Feared by all that swim

    I finally finished rebuilding my 83 Sylvan and I ordered a 40 hp Mariner "tiller" from a marina on EBAY.It is a 99 model and supposedly been completely gone over by a marina in Texas but when I took it out to Buckeye yesterday and hit the throttle it just kept cutting out like it had some bad gas.I was using last years gas I stabilized but I went back to the gas station and got all new gas in a brand new tank with good oil.Went back to the lake and tried again.Kept on spitting and sputtering under a load.I pulled plugs out and they were a little black but I had no new ones with me.I removed fuel filter and it was clean so I figured it wasn't a fuel problem.The primer was tight and the ball was new and tight.I did make the mistake of messing with the 2 carb screws and I think I really through it out of adjustment.Now it wouldn't even get on plane and finally wouldn't start,just backfire.I finally gave up and got new plugs today.The other plugs gap was .50 instead of .40...not sure how critical that was?I played with carb screws until I got motor to fire "pull starting" and now it will start back up good but only time will tell if it will run under a load.Am I missing anything else?
  2. ghart7059

    ghart7059 little fish big story

    a friend of mine told me that you have to adjust the carb under load, that the muffs wont work on bigger motors so i would be prepared to do some minor adjustments on the water

  3. You made a mistake messing with the carbs. They have very specific settings they need to be at. Old gas is also a bad way to test a motor. Even after you got new gas, that old stuff is in the carbs already. Your best bet is probably get a manual and clean the carbs out good and reset the adjustments.
  4. I did some looking on Iboats for your carb settings, but couldn't find anything. The library may have your manual. You'll need to get it on the water or in a tank to determine if everything's ok.
  5. bassteaser1

    bassteaser1 Feared by all that swim

    I got new plugs in and tried to get carb adjust right.It will start and idle now but we'll see how it does here in about an hour.I'm heading to Liebs Island,if it runs good I may do a little fishin,if not I'll be P.O'd and talking to a mechanic.
  6. UFM82

    UFM82 The one others want to be

    OK, it started the first time. It ran bad, but you put fresh fuel in it. Tried it again and it got worse.

    Did you check compression? This is a 2 cylinder? You already did the plugs.

    First, get the old stuff out of the carbs. The plug gap won't kill you but it is best to have them all be close. If you messed with the idle screws, turn them all the way in and then turn them out 2 turns. That'll get you started- adjust from there. You want a smooth idle, but not so smooth the the thing hesitates when you bump the gas. (Too smooth in a 2 stroke means too lean to me) You want to get smooth and then back out 1/4 turn or so.

    If the motor sat before it was shipped it may have crud in the carb bowls. Shouldn't be too tough to pull them and clean them. That is probably the main cause of most outboard woe- dirty carbs.

    Let 'er warm up and then run it. Make sure throttle is opening all the way. Does it cough through the carbs or does it sputter through the exhaust?

    Once you get it running decent even at idle, let it warm up all the way and de-carbon the thing. It'll help it run even better. Sea Foam from NAPA works well- follow the directions.

  7. freyedknot

    freyedknot useless poster

    just curious , if it is a fresh rebuild , did they advise double the oil for a breakinn period? it prolly wouldn,t hurt to check the voltage of your spark.
  8. bassteaser1

    bassteaser1 Feared by all that swim

    The motor was from a Marina and it was a trade in deal.Supposedly the motor had been gone over...Compression check,cleaned carbs,new inpeller and all.I don't beleive my gas was bad because the 9.9 ran on same gas with no problems.I changed and gapped new plugs and took it to the lake today.I took off and it ran alot better,I kept playing with carb adjustment until it seemed to run good at full throttle and idle good but my mid range was surging somewhat.I'll play with adjustment more next time.Thanks for the input guys.