1979 Johnson 15 Hp

[hoganjames]

While out boating this engine jumped out of gear it seemed, the reves were at full but no foward movement, I killed the reves and put the unit back into gear. now I find out that I only have 3/4 trottle and is if very hard to start and is coffing when trottling down, I have changed and checked the spark , Changed the fuel, checked the mixture 50:1. The only thing I have noticed is that on the pull started there was seven teeth now only 2 left it seems that this has happened before. My q is what can I do to get full trottle back and why did it jump out of gear as on this enging there is nearly no rev in netural only in gear so is there some thing else that I need to look at... <br />Thanking you<br />Jim<br />

 

[Xcusme]

Re: 1979 Johnson 15 Hp

There is a possibility that the gear shift connecting rod is out of adjustment, or the clutch dog is worn. This adjustment cam has a detent to limit your throttle while in neutral too. For the manual start gear, there should be 17 teeth. There is a lockout pall on the throttle advance plate that disables the rope starter when the throttle is increased to prevent stripping the teeth off of the starter gear. <br /><br />You will need the service manual to make the shift rod adjustment. Manuals can be ordered from the link at the bottom of this page.

 

[OBJ]

Re: 1979 Johnson 15 Hp

Hey Jim...welcome to iboats....<br /><br />When, as you say, the engine jumped outta gear, did the shift lever move? Or were you running along and the rpms just pick up? It sounds as if your prop hub spun. This is the rubber hub that helps protect the lower unit should you hit something in the water. These rubber hubs can get old and weak and at a certain rpm will spin with out spinning the prop. You get high revs but no speed. Pull the prop off and look at the end nearest the engine. A spun prop will sometimes show signs of little beads of rubber around the hub. You can also make a mark across the hub and aluminum part of the prop. If the same conditions arise again, look at the mark. If they are not lined up, the hub is spun.<br /><br />On the off chance, take a look at the gear lube for any signs of metal pieces. This would indicate some kind of gear/clutch damage.<br /><br />Hard to start.....Give the engine a going over. Don't know when the last time you tuned it up. Check compression, Spark (sounds like you already done so). If you have not rebuilt the carb in a while, do so. Pull the flywheel and check the coils for cracks and frayed wires. Also don't hurt to replace the Flywheel key.<br /><br />I'm taking for granted you refer to the teeth on the pull start gear? I've seen these wear out and break. Has this happened before? Make sure the recoil starter cup alignment tab is in the hole where the starter sits. This keeps it from floppying around when pulled. Post if you have any questions. Thanks<br /><br />Jim