Re: OLD Johnson Super Quiet and Control Box Problem, VERY dangerous things have
Re: OLD Johnson Super Quiet and Control Box Problem, VERY dangerous things have
Your engine is a 1964 40hp Johnson. Although your drawing is fine, with my years of experience, I have no idea what it indicates. It would help if you would also describe the control box you're using.<br /><br />However, regardless of what engine you have, you are describing a manual shift engine that is jumping out of gear, and at times jumping back into gear due to pressure being steadily applied to the shift cable.<br /><br />This type problem is due to the shifter clutch dog and the forward gear lobes being worn, and in your case causes a extremely dangerous situation whereas someone is going to be maimed or killed. To continue to use that engine in its present condition is, to put it mildly, not the wisest thing to do.<br /><br />The above lobe wear can be caused by loose, sloppy linkage, improperly adjusted linkages or cables, or improper shifting by the operator. See the lengthly explanation below.<br /><br />(Jumping Out Of Gear - Manual Type)<br /> <br />This pertains to lower units on all OMC manual shift outboard engines, or any OMC engine with lower units defined as a Shift Assist or a Hydro Electric Shift unit which incorporates a "Shifter Clutch Dog".<br /> <br />Within the lower unit, splined to the prop shaft is what is most often referred to as a clutch dog, hereafter simply called dog. The dog has at least two lobes protruding from it on both ends, facing both forward and reverse gear. The forward and reverse gears also have lobes built into them near their center area. When the engine is running, in neutral, the gears are spinning constantly via the driveshaft being connected directly to the powerhead crankshaft, but the propeller does not turn due to the fact that the dog is centered between the two gears, and the dog lobes are not touching either of the gear lobes.<br /> <br />When the unit is put into either gear, shift linkages force the dog (and its lobes of course) to engage the lobes of the the gear. The lobes of the spinning gear grab the lobes of the dog, and since the dog is splined to the prop shaft, the propeller turns.<br /><br />The lobes of the dog and gears are percisely machined, most with right angled edges that could be installed in either direction, and some with angles slightly varied that must be installed in one direction only (one end only must face the propeller). Dogs that can be installed in one direction only, if reversed, even if the dog and both gears were new.... would jump out of gear almost immediately. Keep in mind that the lobes are percisely machined with sharp angles!<br /> <br />Due to improper adjustment or worn shift linkages, but usually due to improper slow shifting, those percisely machined sharp edges of the lobes become slightly rounded. Now, with those lobes rounded, as the rpms increase, the pressure of the gear lobes upon the dog lobes increases to a point whereas they are forced apart (jumping out of gear), and due (usually) to the shift cable keeping tension on the engines shift linkages..... the unit is forced back into gear giving one the sensation that the engine has hit something, and the cycle continues.<br /> <br />Some boaters have the mistaken belief that shifting slowly is taking it easy on all of the shifting components..... Wrong! Shifting slowly allows those percisely machined sharp edges of the dog and gears to click, clank, bang, slam against each other many times before they are finally forced into each other..... and this is what rounds those edges off! The proper way to shift is to snap the unit into gear as quickly as possible.
