1973 4HP Lightwin No Thrust

Hello,

I recently purchased a 4HP Lightwin as a kicker for my sailboat. First time I was out, things ran great, no problems. The second time I was out things were going great until I was motoring into the boat launch. As I was heading in the motor revved up very high, so I immediately cut the throttle. I started the engine back up, and it sounded fine, but when I looked down at the propeller I realized it was no longer moving. I've been stalking this forum a bit to figure out where to start. So far I've removed the propeller and checked the drive pin and the hub. The drive pin is still one solid piece and is definitely not the problem. The clutch still has a nice tight fit with the hub, and the hub is stuck solidly in the propeller. So the next thing I tried was spinning the flywheel by hand. When I do this there is no movement on the prop shaft (there should be right). My best guess is that the problem exists in the prop shaft, pinion, or drive shaft. So I was planning on getting a service manual and taking the Lower Unit apart. Am I on the right track or am I missing something obvious? If it makes any difference the flywheel spins easily.

Thanks,
Jake

Re: 1973 4HP Lightwin No Thrust

The 4 horse is as simple as it gets when it comes to an outboard. In the lower unit there are two gears and that is it. Pull the lower unit and make sure the drive shaft is good. If it is pull the lower unit apart and take a look at the gears. You might as well as replace the impeller while you are investigating everything. Make sure you don't lose key when you pull the drive shaft out of the lower unit. It goes together just like the parts diagram.

http://www.marineengine.com/parts/j...er=Evinrude&section=Gearcase+-+Standard+Drive

Re: 1973 4HP Lightwin No Thrust

Alright, I figured that would be the next step. Right now I'm fighting old hardware that I'm guessing hasn't come apart since 1973. I bought some kanokroil to get the prop off, so I'm spraying that on these screws every night and trying again. I really don't want to strip them. So far I was able to get the top one off the "Gearcase HD & Bushing Assembly" but the bottom one and the other gearcase screws are being extremely stubborn.

Re: 1973 4HP Lightwin No Thrust

Sometimes you have to use a little heat to get stubborn bolts out.

Re: 1973 4HP Lightwin No Thrust

My money is on the driveshaft having spun out of the crankshaft. Not uncommon on those little motors, particularly if a previous servicing didn't include replacing the upper shaft o-ring and re-greasing the splines before reassembly. Results in the crank splines rusting, and eventually failing.

Re: 1973 4HP Lightwin No Thrust

Whew,

Long delay, but I finally got the lower unit off. I didn't strip anything, but some of these screws are close, I'll probably just replace all the screws that hold the lower unit on.

Chinewalker, you are completely correct the crankshaft is spun. With the lower unit off, the prop shaft and drive shaft spin great. The drive shaft was rusted pretty well into the crankshaft. I was able to get it out by turning the motor upsidedown and spraying plenty of Kanokroil down the drive shaft. I let it soak for a bit then turned it back rightside up, and then it came loose with a bit of wiggling and pulling. The drive shaft splines look like they are full of rust and maybe bits of the crankshaft splines. So to me it looks like the drive shaft can stay but the crankshaft will need to be replaced. Am I right, or does the drive shaft need to go too?

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Thanks for all the help so far!