My Evinrude 4hp Motor Won't crank....help

[mountforever]

So I have this really sweet Evinrude 4hp motor. 2 stroke 2 cycle. Model 4636M form 1976. The other day I was cruising into Clipper Cove and the motor started having a weird putter to it. Right before I landed the motor turned off with a "clunk". Now the pull start won't rotate the rewind starter/magneto cover. I can rotate the in reverse and when the pullstart gets it back to that certain point it won't go past it. But up until that point I can tell that I am getting spark and compression....Just not enough to get it going. what got stuck..or broke?

[erps]

sounds bad. the way it locks up makes me think a rod came loose. This would allow the engine to rotate backwards, but when you rotate it forward, it comes in contact with the displaced rod. Pull the spark plugs out and check to see that both pistons are going up and down and you move flywheel as much as you can.

[pschoonveld]

I second erps' guess. The easiest to do is to get a dowel or similar, pull the plug and stick it through the hole. If the piston moves back just from the pressure of the dowel, you have a broken rod or crank. If it doesn't move smoothly when pulling the rope, the same is likely true.

There are many people that would love to rebuild an old classic like this, but if you don't know how to do it yourself, you're better off to look for a new or secondhand motor.

[Capnblu]

More often, than not your magneto let go. Look up under the flywheel, and see if you can see where the magneto might be hitting the flywheel. After that I would suspect a rod cap let go.

[mountforever]

there's definitely nothing obstructing the flywheel. how do i eve take that off to look under it? and what do you think it would cost me to replace a rod? do you think any shop manual would show me how to do it?

[sigmasailor]

If a rod is broken (or piston/pin/bearing failure) there will probably be more damage than the broken rod/part itself and a complete overhaul is called for.
If you have this done professionally it may cost you (a lot) more than a new (second hand) outboard.
If you can do it yourself depends on your skills and availibilty of tools; maybe you need to clean up the crankshaft or other damaged parts.
Maybe you can find someone wth love for these old engines to help you overhaul it with you?

The big question is: how much are you in love with this old motor.

[erps]

More often, than not your magneto let go.

Good call. It would have taken me a little more head scratching and skinned knuckles before I got there.

there's definitely nothing obstructing the flywheel. how do i eve take that off to look under it?

That big nut on top presses the flywheel down on a tapered shaft. You'll want to loose that a few turns but leave it on so it doesn't jump off in the next step. If you have a puller, apply it, if not get a friend and two big screw drivers. Wedge the two screw drivers underneath the flywheel on opposite sides and apply some prying pressure and then have your friend give that big nut on top of the tapered shaft a couple wacks with a big hammer to see if she'll pop loose. Leave that big nut even with the top of the threaded shaft so you don't booger it up.

[timebandit]

Does this motor have a 'start in neutral only' feature?

Maybe you just need to put it in neutral to unlock the the starter.

Then you might look for water in the gas for the reason the motor wanted to stop in the first place.

[mountforever]

I'm thinking something is blocking the flywheel. Before the big clunk at the end it sounded like someone had a put a baseball card in your bicycle spokes and there was that puttering. I'm guessing something is blocking the flywheel. I'll try tonight.