Throttle linkage slop

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    Matthew Pieklik

    US Member - 2 Years
    Replies: 21
    Topics: 19

    Hi All , I am working on a classic in training, A 1979 15 HP Johnson. 15R79E 2 questions, I have almost 1/4 turn of play in the throttle handle. I see the gears linking the handle to the mag plate shaft next to the power head are nylon and seems to be the source of the slop. Common problem? To replace them, will this require a power head removal along with a tiller handle removal? Any tricks to this?

    Question 2: Thermostat, I am sure it is original and most likely stuck open. To remove the cover plate on the head and R&R the Thermostat, Will that require a power head removal also?

    Thanks , Matt.


    US Member - 2 Years
    Replies: 3325
    Topics: 49

    Yes, this sloppy throttle linkage is a common problem for these engines. Believe it or not, the slop usually comes from the plastic shaft and the way it fits into the two plastic gears…

    #52, 53, and 65 The square ends of the plastic shaft get sloppy inside the two gears.

    What makes you think the thermostat is stuck open? Is the engine actually running cold? If so, the thermostat water cover can be removed without pulling the powerhead, but it is a pain in the butt…Start by removing the cover latch to gain a little more room behind the water cover. Loosening up the two rear lower motor pan mounts will help also, this might allow the lower pan to drop down just a bit. Don’t remove the mount bolts completely, the mount washers will slide out and get lost in the lower motor cover.

    Has this engine been used in salt water? If so, you may want to consider doing a more thorough cooling system overhaul which does involve pulling the powerhead. Changes were made the the upper water tube grommet in 1979 which were troublesome. The grommet is not fully supported by the water tube, which allows salt to collapse the grommet above the top of the water tube……

    • This reply was modified 3 months, 3 weeks ago by Avatarfleetwin. Reason: grammar

    Canada Member - 2 Years
    Replies: 4534
    Topics: 432

    The 9.9/15 horse motors are notorious for developing slop in the throttle linkage but there is a way to tighten it up a bit without pulling the powerhead by using brass shim stock.

    Once the tiller is removed, the snap ring, # 67 must be undone to remove the gear, # 65, and the shaft, #53. A large screw can be inserted into the pin, #107, to remove it before removing the gears # 52 and #109, if desired. The shaft has alignment grooves on each square end and can only go in its corresponding gear one way so the side without the grooves is the side which will get shimmed.

    I can’t find any photos so I’ll try to describe it the best I can. The shim stock gets cut into a strip about 1/4″ wide and an inch or so long. An eighth to a quarter inch of one end gets bent over ninety degrees and inserted into the # 52 and 65 gears on the side without the alignment grooves before the shaft is installed. The bent end is what holds it in place. If the parts are really worn, a second shim can be installed on the other side without the alignment grooves. The thickness of the shim(s) needed will vary depending on the amount of wear but they shouldn’t be too thick to prevent the shaft from sliding in the gears.

    This is my poor mans approach to solving this problem and I’ve been doing it for years with great success! I do have some of these motors apart right now so I’ll try and get some photos up later.

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