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  1. #1

    Default 9.8 getting harder to start

    I have a 9.8 EPUL bought new in 2014, actually bought two, to power a 36 sailing catamaran. The motors have been very reliable. They now have about 300 hours on them. I always run them dry of fuel and have used them regularly, changed oil, plugs, and lower unit oil often. One of them is starting to behave a little differently. It doesn't start as easily. It then takes a minute or two after it does start, to smooth out. I just did a long trip and changed the oil after a weeks worth of steady running, avg ten hours a day. I started out with fresh oil. The oil in this motor was noticeably dirtier than the other engine, when I got home . Is it time to start messing with the carb? I have no experience with carb cleaning, replacement etc., but have learned to do all the other stuff, including changing impellers. Should i leave this one to the pro's? My problem is that the motors are difficult to take off the boat; they are mounted on a vertical sliding system, and a huge pain to take off, get them down the dock, and to a mechanic. Also found a bit of plastic bag on the prop. i cleaned it up and think I got it all. Could that extra load account for the dirtier oil? Any advice greatly appreciated.

  2. #2
    Join Date
    Mar 2010
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    Hamburg, NY, USA
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    Default Re: 9.8 getting harder to start

    OK, you have a pair of MFS9.8A3EPUL motors. If the oil on one gets darker faster, you may have more blow-by, or that motor may not have as good combustion. That could also result in more carbon in the chambers, which might make it take longer to smooth out. Never hurts to do a Proper carb cleaning. I would also do a leak-down test on that motor (requires compressed air). Of course, see what the plugs look like; that tells a lot. Yes, a plastic bag would cause more load on that motor, but probably not cause the other issues (starting) that bad. Of course Verify that the oil is not over full. Not even a drop.
    Paul
    Certified Tohatsu TLDI Technician
    Hamburg, NY USA

  3. #3
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    Mar 2010
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    Default Re: 9.8 getting harder to start

    It wouldn't hurt to verify compression. If that's good (probably is), then the leak-down test is called for.
    Paul
    Certified Tohatsu TLDI Technician
    Hamburg, NY USA

  4. #4

    Default Re: 9.8 getting harder to start

    Quote Originally Posted by pvanv View Post
    It wouldn't hurt to verify compression. If that's good (probably is), then the leak-down test is called for.
    It was a casual thing, when I noticed the darker oil. I hadn't been paying that much attention to the oil color before, when I changed the oil on the first motor. I had changed both engine oils in Key largo before leaving to come home to st simons. I ran them pretty hard a couple of days prob 10 hrs a day for a few days. probably total of 50-60 hrs each. (I was motor sailing part of the time, and sailing part of the time so I didnt keep accurate hour records) The plugs were new when I left home, to go down, so they have 100 hours or so on them. I checked them btw, after the first post here, and they were dry and clean. So I cant really say how much darker the oil was, I only noticed it in passing. When changing the oil, i do it in situ on the boat because of the pita in removing the engines etc., so they might not be drained as completely as they could be if they were laying on their sides. Anyway, how do I check the compression, and do a leak down test? Is this something one can do without special tools? And the carb cleaning- do I need to get a kit? and what is sonic cleaning? sorry to bombard you with so many questions. I assume the sluggish starting issue will only get worse. Would a fuel additive help? I try and use fresh gas, but, the way I do it, I go out for a sail, maybe burn a half gallon, and then replace it with marine fuel from the service station. So i am constantly topping off the 3 gal. tank. About once a week on average. FWIW, I always run them dry and never use ethanol. Thanks!

  5. #5

    Default Re: 9.8 getting harder to start

    Ok I googled leak down test, and I get it now. I think it is beyond my level of expertise, though. Thanks for any recommendations

  6. #6
    Join Date
    Mar 2010
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    Default Re: 9.8 getting harder to start

    Yes, if starting is getting harder, it likely will get worse over time. With over 300 hours on the motors, a new carb kit in each would not hurt, but may not be required... but odds are the o-ring for the carb bowls has white corrosion that needs cleaned... there is a new one in the kit. While the carbs are off for cleaning (before installing the new kits), using an ultrasonic cleaner is a good idea; it will help to dislodge any varnishing. Your local shop should have one. You can pull the carbs while the motors are on the boat, and take them to the shop. You will need a long extension for a 10mm socket to get to the carb mounting bolts, and you may need new carb base gaskets; just don't drop any bits in the water!

    Oil changes for the motor oil should be fine with the motors on the boat... have the motors tilted down so all the oil goes to the bottom of the sumps. That should be done every 50 hours or so. Changing the LU lube may be trickier, depending on whether you can get the LU out of the water in order to drain the lube. Remember that about 1/2 to 3/4 on the dipstick is plenty of oil; they only hold about 3/4 of a quart. Never over fill. Not even a drop high.

    Since the plugs look good, the motor health is probably OK. May just be some varnishing in the low speed circuit of that one carb causing starting issues. Yes, avoiding alcohols is good, and running dry is good. As long as the fuel is only about 30 days old, the fuel should not be spoiling much, so you are doing everything right.

    In your situation, I would pull the carbs, have them professionally cleaned, and install new kits... and then see how everything works.
    Paul
    Certified Tohatsu TLDI Technician
    Hamburg, NY USA

  7. #7

    Default Re: 9.8 getting harder to start

    I see that Marine engine.com dosent sell Tohatsu parts. I have ordered the shop manual, and intend to pull this carb and have it cleaned. My question now is what should I expect to get in the kit. On Amazon, they sell one, but some folks there complain that the jets aren't included. Should I expect to replace them or just clean what I have? Any recommendations as to where to buy a carb kit? Thanks.

  8. #8
    Join Date
    Mar 2010
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    Default Re: 9.8 getting harder to start

    Firstly, use a Factory service manual, not an aftermarket door stop.
    Part #: 003-21056-1 List Price (MSRP): $41.67

    Secondly, use a Factory carb kit, which does not include jets, since there are different jets depending on altitude. Clean the originals. The kit will have a new float, needle, and associated gaskets and screws.

    Part #: 3V1871220M List Price (MSRP): $55.27

    You will need a long 3/8 extension to access the inner carb bolt. Any Tohatsu dealer (even me) can provide you with the OEM parts and manuals.
    Paul
    Certified Tohatsu TLDI Technician
    Hamburg, NY USA

  9. #9

    Default Re: 9.8 getting harder to start

    Tohatsu service manual speifies "konishi bond" G17 to seat the narrow gasket that separates the two main pieces of the carb. Is there an American equivalent product? Thanks.

  10. #10

    Default Re: 9.8 getting harder to start

    It is the float chamber gasket

  11. #11
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    Mar 2010
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    Default Re: 9.8 getting harder to start

    No gasket material needed. It's an o-ring. The G17 is used to bond the o-ring to the bowl chamber at the factory. We never use any sealer when attaching the chamber to the carb body.
    Paul
    Certified Tohatsu TLDI Technician
    Hamburg, NY USA

  12. #12

    Default Re: 9.8 getting harder to start

    Thanks Paul for all your help!
    Re gasoline: the Tohatsu manual specifies regular unleaded gas, then it says in parenthesis (research 90 octane or more) Not sure what that means. At the fuel pumps here marine gas is available in 87 octane only. So which is better ; higher grade gas with 10% ethanol added, or 87 octane with no ethanol?

  13. #13
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    Mar 2010
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    Default Re: 9.8 getting harder to start

    Quote Originally Posted by spiritofstsimons View Post
    Thanks Paul for all your help!
    Re gasoline: the Tohatsu manual specifies regular unleaded gas, then it says in parenthesis (research 90 octane or more) Not sure what that means. At the fuel pumps here marine gas is available in 87 octane only. So which is better ; higher grade gas with 10% ethanol added, or 87 octane with no ethanol?
    There are two octane ratings: Research and Motor. Research is always higher. The number at the pump is usually an average (R+M/2). 87 is plenty. Skip any ethanol if possible.
    Paul
    Certified Tohatsu TLDI Technician
    Hamburg, NY USA

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