What is the proper procedure to set points on a 1971 7.5HP outboard motor?

Answer 1

First find the points on the engine. They are under the flywheel on the top of the engine. If you are real lucky, the flywheel will have holes in the top that you can reach the points through (but I doubt that year does). If the flywheel doesn't have access holes, then you must remove the flywheel.

To remove the flywheel, use a large screwdriver braced against a strong point on the engine block to keep the flywheel from turning. MAKE SURE YOU FIND A STRONG PLACE TO BRACE THE SCREWDRIVER OR YOU CAN BREAK SOMETHING. Use a socket wrench to loosen the nut in the center of the flywheel (you usually cannot get anything but a socket wrench on this nut because the nut is recessed in the flywheel). Having a second person to hold the screwdriver makes this a lot easier.

Loosen the nut until the nut is flush with the top of the crankshaft. Leaving the nut on will help keep you from damaging the end of the crankshaft. If the nut is flush with the top of the crank shaft and there is no gap under the nut, then do this: Remove the nut and take off the washer that is under it and then put the nut back on - flush with the top of the crankshaft.

Now use a wheel puller to remove the flywheel. Oh, you don't have a wheel puller big enough to do this? :) OK, then do this ...

Use your screw driver to pry up lightly under the flywheel. Now whack the top of the crankshaft with a hammer. Try real hard to have the hammer hit the crankshaft flat and in the center. If you hit it crooked, you will damage the crankshaft and nut more. Did the flywheel pop loose? No, then you must hit it harder! This is where having the nut flush with the top of the crankshaft is very important. If the nut is too low, then the crankshaft end will be badly damaged. If the nut is too high, then the nut will be badly damaged. Don't loose the small key that indexes the flywheel to the crankshaft.

CAUTION - Even when done correctly, I can't promise the hammer method won't damage any thing. I highly recommend a wheel puller, but I know your not going to go out and buy one for a 35 year old outboard. :) Please don't blame me if you break something. Note, in the unlikely case that you have a wheel puller, you should still use a hammer. You tighten the wheel puller up tight and then strike the top of the puller with the hammer. If you just keep cranking on the wheel puller without tapping with a hammer, you will probably bend or break the flywheel before it comes off.

OK, now that you reached the points, I recommend that you replace them with a new set. If you don't replace them then you really need to file them. Get a "point file", they are cheep.

After the points are filed, turn the flywheel until the points are wide open. You should find the points open twice for each revolution of the crankshaft (once for each cylinder). You can see the small bumps on the cam that opens the points. Turn the crankshaft until the rubbing block on the points sits on top of one of these bumps. You can set the flywheel back lightly on the crankshaft to turn it. If it sticks on the crankshaft, a small tap with the hammer will pop it back off (you don't need to us the nut for this light tap).

Loosen the screws that attach the points, but not very much. You want to be able to move the points, but you need the screws tight enough to hold that points from moving when you don't want them to. There is probably a slot in the plate the points are attached to where you can insert a screw driver to make it easier to make small adjustments to the points. Using a set a feeler gauges (yes, you will need to buy these too) adjust the points to the correct gap. If you are lucky, the correct gap setting will be cast into the flywheel somewhere. It should be a number something like .025 inches. If you can't find the number on the engine, then try the web of calling an outboard mechanic. If you can't find gap specification anywhere, then as a last resort use .025 inches. This should be close enough to give good results.

How do you use the feeler gauges to tell if the gap is correct? First, make sure you hold the gauges straight between the points. You should feel just a little drag on the gauge, if you don't feel any drag, then the points are too loose. You should be able to easily inset the gauge between the points with out having to wiggle it at all. And, you should be able to pull it out without any noticeable closing of the points. When you think you have it right, select a feeler gauge that is .002 inches thinner than what you were using. This gauge should move between the points with no drag at all. If it has drag, then the points are too tight.

When the you have them adjusted correctly, tighten the screws. Then, check the gap again. The points often move when you tighten the screws, so you may have to try a few time, either starting with the points a little wide or a little tight so that they come out right after you tighten the screws.

Finally, put the flywheel back on. Make sure you have the key in the crank shaft and that you don't knock it out when you put the flywheel on. If the key is not in there, the flywheel can spin on the crankshaft and the engine may not run.

I hop this helps. Good luck.