How to set the points gap on 1971 25R71 25 hp Johnson

I understand that I can temporarily put the flywheel nut back on the cam bolt and use a wrench to align a certain part of the cam with the point being set (for each point) ?

Where on the cam shaft needs to be aligned with the point I'm setting? The high? Low? I don't remember seeing any kind of mark on the cam shaft that *precisely* marks the highest or lowest point?

Can someone please explain the procedure?

Re: How to set the points gap on 1971 25R71 25 hp Johnson

Don't make it so complicated. As with ANY engine that uses points, merely turn the shaft till the points open at their maximum. Then adjust the gap to specs, in this case .020"

That will get it close enough. If you want to do it the "right" way, a special timing fixture is required. But it is not an absolute requirement to do it that way.

Re: How to set the points gap on 1971 25R71 25 hp Johnson

I'll chime in and say that using the timing fixture was very easy! For what it's worth, I just went through this on my 1971 Johnson 25hp - I picked up one of the timing fixtures from F_R, and it was money well spent (especially if you will be working on multiple motors).

Ken

Re: How to set the points gap on 1971 25R71 25 hp Johnson

F_R said:

Don't make it so complicated. As with ANY engine that uses points, merely turn the shaft till the points open at their maximum. Then adjust the gap to specs, in this case .020"

That will get it close enough. If you want to do it the "right" way, a special timing fixture is required. But it is not an absolute requirement to do it that way.

Click to expand...

Well, when I turn the shaft using the flywheel nut and a wrench (clockwise), the point I'm working on appears to open up the widest when there is no apparent marking on the shaft that could be used as the guide instead of my own eyes. The area on the shaft is close to the key but not at the key, maybe 1/4" away or more. I'm aligning this imaginary area on the shaft with the rubbing portion of the point.

My guess was that I should be aligning the point rubbers with some marking on the shaft meant for that purpose. And what about top cylinder, bottom cylinder... as long as each point is 180 degrees apart in being opened/closed, cylinder order shouldn't matter?

Here's the results I have seen:

-without the points even being set correctly, the motor ran smooth, I had installed them and forgot to set gaps, pure luck?
-setting the points using the shaft key aligned with the point rubber, no crank
-setting the points using the raised thin "mark" next to the word "TOP" on the shaft, motor cranks but runs choppy

I'm turning the shaft clockwise using the flywheel nut slowly using a wrench and precisely stopping my mark point at the rubber portion of each point I'm setting.

All new points, coils, condensers.

Re: How to set the points gap on 1971 25R71 25 hp Johnson

try setting them with the "rubber" aligned with the O in TOP...and yes 180 degs. rotation set the other set the same way....it's fires top-bottom , or 1-2...setting the points has no bearing on this...the points must be really clean to function properly, no oil or oxidation on the faces

Re: How to set the points gap on 1971 25R71 25 hp Johnson

Ditto. This link should help too. It's for a different model, but the steps are the same.


http://www.outboard-boat-motor-repa...on 3 HP 1952-1967 Ignition System Tune-up.htm

Re: How to set the points gap on 1971 25R71 25 hp Johnson

AlTn said:

try setting them with the "rubber" aligned with the O in TOP...and yes 180 degs. rotation set the other set the same way....it's fires top-bottom , or 1-2...setting the points has no bearing on this...the points must be really clean to function properly, no oil or oxidation on the faces

Click to expand...

Before I read this, I went out there and set the points to the P in "TOP" and it cranks and runs a lot better... I also made sure the gap setter was snug when I slid it between the contacts.

Re: How to set the points gap on 1971 25R71 25 hp Johnson

Cool. The letter "O" is just a general reference point. You want to set the points to .020" at the highest spot on the cam lobe. SOmetimes that's closer to the "O", or the "P". However, as you've learned, it's just as important that the points be set to the same gap as one another, if not .020" exactly. Glad you got her running. Vroom, vroom!

Re: How to set the points gap on 1971 25R71 25 hp Johnson

kfa4303 said:

Cool. The letter "O" is just a general reference point. You want to set the points to .020" at the highest spot on the cam lobe. SOmetimes that's closer to the "O", or the "P". However, as you've learned, it's just as important that the points be set to the same gap as one another, if not .020" exactly. Glad you got her running. Vroom, vroom!

Click to expand...

I blame this on the way I think, but... I just hope she stays running that smooth. I took a video with my cell phone of my just tapping the ignition key and the motor purrs right up. Of course it took me about 10 tries to crank her 5 minutes prior even after priming and pushing the choke in and the throttle lever at midway.

I plan on going to the best plugs possible based on veteran advice on this motor. The plugs aren't fouled but they might not be the best brand for the age of this motor? I haven't even examined the brand on them yet. Just removed them once to see if they were clean, which they were.

It's just wishful thinking to want the motor to run even smoother but sometimes trying to keep improving something we break it.

Re: How to set the points gap on 1971 25R71 25 hp Johnson

The distance the points open doesn't matter a hill of beans. It is WHEN they open that matters. However, the distance is related to the when. Set the gap wider, and that makes the rubbing block contact the cam slope earlier. And vise-versa. That is the reason for the timing fixture. With it, you set them for "when", not "now far". Through experimentation, you have acheived the desired results, so good for you.

Re: How to set the points gap on 1971 25R71 25 hp Johnson

Any tips on getting the flywheel back off the shaft without scarring up the shaft using pliers or channel locks?

Re: How to set the points gap on 1971 25R71 25 hp Johnson

F_R said:

The distance the points open doesn't matter a hill of beans. It is WHEN they open that matters. However, the distance is related to the when. Set the gap wider, and that makes the rubbing block contact the cam slope earlier. And vise-versa. That is the reason for the timing fixture. With it, you set them for "when", not "now far". Through experimentation, you have acheived the desired results, so good for you.

Click to expand...

My flywheel nut looks like I've had the channel locks to it for a week. Because I have. I didn't have a wrench that size so I've been using the locks. The nut looks rough but it works. In other words, I've removed that dang flywheel probably 20 times trying to get things right, but most of that was before I really understood what I needed to be doing. My learning curve starts gradual then climbs steep right at the end. heheh.

Re: How to set the points gap on 1971 25R71 25 hp Johnson

Maybe someone knows a better way, but I'd stick a block of wood in the prop with it in gear and then loosen the flywheel nut...

For setting points, I've always turned the crankshaft by carefully tapping (rotating) the prop while in forward gear instead of putting the nut back on without FW.

Re: How to set the points gap on 1971 25R71 25 hp Johnson

as I understand it, you are putting the channel locks on the tapered end of the crankshaft to remove the f/w after you've used the flywheel to turn the crank to set the points?...all you really need to do is use sludge's method, or turn the flywheel by hand w/o ever putting the nut on and tightening it..the key will orient it and the fit will be tight enough to allow you to turn it with the sparkplugs out..scarring the end of the crankshaft isn't a good idea

Re: How to set the points gap on 1971 25R71 25 hp Johnson

Here's a pic for the best way to remove the flywheel. I would invest in a proper size socket for the flywheel nut itself, however. If it gets too chewed up, you can replace it with a SS nut of the same size.




http://www.duckworksmagazine.com/07/columns/max/index1.htm