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First post and a few questions on 73 merc 20hp

T

Tenzero1

New member
Hey all,

After a long time lurking, I am glad to have finally joined! I was recently gifted a 1973 20hp that was given not working. After looking it over a bit I have found that the larger wire running from the stator to the coils is cracking badly. Also, one of the smaller wire's running to the opposing coil has been chewed through by mice. This is as far as I have gotten in diagnosing any issues aside from turning the motor over to make sure it isn't siezed and has compression. Based on what I have seen, I have a few questions...

1. How difficult is it to replace the wires coming out of the stator/ how do I access them?
2. What wire is best to use, or is any standard wire the same gauge acceptable?
3. If I am getting down to the stator should I replace or do anything while I have it apart?

At this point the motor has the wrap shield and the cowl removed, but I am hesitant to remove anything further in fear of losing parts or order.

Any help is appreciated!

-Thor
 
...."How difficult is it to replace the wires coming out of the stator/ how do I access them?

Virtually impossible--and I've tried.

What you have is the infamous Phase Maker ignition system, whichuses both points (operating assbackwards) and electronics--the worse system ever devised. The only solution is to buy a new CDI stator ($$). If you do, be sure to eliminate the kill switch completely (and ground that lead securely to the block. The kill circuit works assbackwards on these.) That improves the life of the stator.

Jeff
 
Geeeez I may have to try and salvage the wiring and splice into what I can. That's a bummer! Is there any type of wire that works better or just standard wire of the same gauge? Thanks!
 
what color is the stripe i think 1973 was blue so you shouldn't have the phasemaker. you should have the first year of the cdi ignition which is much easier to repair need your model # to be sure
 
Good point: the P M system was so bad Merc started getting rid of them in mid-year.

Question: Does you motor have an external switch box?

Jeff
 
I believe I was dyslexic when reading he serial number, its pretty worn the serial is 3062727 which makes it a year or so older then I had said unfortunately.

There isn't an external switchbox.
 
Find a manual at the library or online to find the values for the stator to test it make sure its good also do a compression test. I just did one of these for my friend of mine I will say the phasemaker ignition runs better than the cdi model. Here is what I found on it you probably won't be able to repair the stator I replaced it for between 200-300 dollars aftermarket then i replaced the coils because when I disconnected the wires the studs loosened up and had to be replaced $100 apiece mercury only no aftermarket available do not put the later coils in these they are not the same. I reused the points just cleaned them up reset them. Also rebuilt the carb and replaced the fuel pump. But it is a very nice running motor if you do decide to get it running never use the kill switch unless it is in the water. When on muffs use the choke
 
So I took it apart to the stator today and I don't think I can get any usable wire unfortunately. So now the question is, is it worth it to buy a new stator? Or is this a motor that just isn't worth sinking money into? I don't have a gauge to test compression, but if it is inexpensive I can get one.
 
If it does have good compression is it worth getting a new stator?

Also, how do I remove the plate that held the flywheel down? I can't seem to find a way to remove the stator without taking that out.
 
should be a bolt and washer holding the flywheel down take it off pull the flywheel and the stator is right there. What kind of condition is the motor in if you stick money into it you may or may not be able to sell it for what you have in it. lowerunits are hard to find because its backwards if it was me i would make it a hobby motor fix it as i wanted to and buy something newer with more parts availability.
 
I have the flywheel off, but the stator still cannot be removed without taking another part out.

I think I will have to sell it off. I want to get better parts but not for that much money. I can buy a newer motor for less sadly.
 
Agreed. Where you can slap an magneto on the smaller P M nightmares, that motor has the points cam machined into the block. And since it works the points assbackwards (close to fire the plugs) you can't use it with a magneto.

Jeff
 
A small update. I ended up bartering some things for another motor only it is a 1972 and has a different stator. My new question is, can I take the ignition system from the 72 and put it in my 71 or is it not compatible?
 
The answer is "maybe".

I'm fairly certain you will not find any manual that will tell you if/how to do it.

I have considered trying to "Frankenstein" an ignition or two myself over the years but never quite got to it yet to see if/how difficult it is to do or if it would work or simply create more issues.

My "sense" is that it should be doable - after all the motor itself doesn't know (or care) where it's getting it's spark from, so as long as you could get the system to work (generate power) and trigger properly (correct timing), there is no reason it "shouldn't work".

Of course that's assuming that you can get all the bits/pieces and any linkages mounted and working together.
 
they should be the same as the phasemaker was on 70-72 models as long as its a 20 hp should interchange. You may have an aftermarket stator that's why it looks different
 
Hmm either way I think it's worth a shot depending on compression testing. If my new motor has better compression I will keep it on that one. Updates to follow if anyone is interested.
 
Compression tests on the older motor were 120 and 130 and 150 for both calendars on the new motor. Looks like I will be reviving the newer motor!
 
Not sure if anyone is still interested, but I have a few updates.

I ended up taking what I could off of the 71 and put it into the 72. The 72 is not a pretty motor, but it runs well.

I found a 73 20 HP and bought that for $80 then put about $150 into it with carb cleaning, lower unit seals, and impeller. It runs very well.

I have a 69 9.8 HP that was given to me as working but was told that it doesn't run well when it's wise open. I am going to buy new plugs soon to see if that helps. Otherwise, I am open to suggestions. I assume a carb cleaning would help.
 
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