I Got Me a Mercury !!!

tpenfield

tpenfield

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The new(er) (blue label) Merc is not feeling well today. I was going out to the big boat, but the Merc 7.5 had other things in mind. I think the ignition is intermittent. I'll have to do some more testing to see for sure. I tried starting fluid, new spark plugs, but nothing. Last time out must have been a fluke.

While the Blue Merc is being diagnosed, I'm thinking of picking up a 2 cylinder 4 (ish) HP JohnnyRude engine. My other motor . . . the little 3 HP Yammy really does not run all that well and it has its own set of starting issues. It is a one cylinder, and does not idle well. I think single cylinder engines are not meant to idle down low, unless they have sizable flywheels. I've noticed that with outdoor power equipment . . .1,200 RPM idle is about all you can get.

Meanwhile the toolbox will be open for the Blue Merc. . .
 
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racerone

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A 6 HP Johnson / Evinrude from 1966 to 1979 are ideal.----The 66 to 76 used the universal ( low cost ) magneto.-----Need to know how to clean breaker points on occasion.----The 77 to 79 had electronic ignition.-----These are just wonderful motors if in good condition.
 
redneck joe

redneck joe

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That was always dad's kicker on any boat he had, even the 25' cruiser. I had one for a bit as well, perfect.
 
tpenfield

tpenfield

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I have a 4.5 HP Johnson from the 1980's (maybe 1984) . . . but it is a long shaft. It was a bit finicky when I first got it, but now it runs pretty well.

Maybe find its short shaft cousin.

My plan is to go through the Blue Merc's ignition system, test the coils, replace wires, etc. It would be nice it I could have it as my go-to motor for a while.
 
tpenfield

tpenfield

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My game plan for the Blue Merc is to pop the flywheel off and go through the ignition stator wiring, replacing sections of wire as needed. Since the motor actually worked for me on several occasions, I am thinking that the problem may be with connections vs. bad coils.
 
tpenfield

tpenfield

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I'm on my way to CA and will be there for 2 weeks. Plenty of time to read up on 'Phase Maker' ignition systems, which I believe is what Mercury has in these early-1970's motors. :unsure:
 
nola mike

nola mike

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tpenfield said:
The new(er) (blue label) Merc is not feeling well today. I was going out to the big boat, but the Merc 7.5 had other things in mind. I think the ignition is intermittent. I'll have to do some more testing to see for sure. I tried starting fluid, new spark plugs, but nothing. Last time out must have been a fluke.

While the Blue Merc is being diagnosed, I'm thinking of picking up a 2 cylinder 4 (ish) HP JohnnyRude engine. My other motor . . . the little 3 HP Yammy really does not run all that well and it has its own set of starting issues. It is a one cylinder, and does not idle well. I think single cylinder engines are not meant to idle down low, unless they have sizable flywheels. I've noticed that with outdoor power equipment . . .1,200 RPM idle is about all you can get.

Meanwhile the toolbox will be open for the Blue Merc. . .
Click to expand...
Get a DVA. Or you might want to build one. Not sure what type of electronic ignition is in that one, but I had a hell of a time last year chasing down an ignition problem on my 25 hp. Intermittent weak/no spark. I fired up the parts cannon to no avail, but having the DVA would have saved me a ton of time. Check out this thread:

'04 Merc 25hp dead(ish) cylinder

Been chasing some poor running for the last few weeks. Originally was running well, but had a couple of episodes where it died at speed, difficult to restart. Noticed fuel leaking from somewhere around the carb. Rebuilt the carb with a crappy kit. Took it out once and all the gaskets...
forums.iboats.com forums.iboats.com
 
tpenfield

tpenfield

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Thanks @nola mike . . . The engine has what is known as a 'phase maker' ignition, which I believe was a lead-in to the electronic ignitions.

Basically the stator creates fairly high voltage and instead of 'breaker points' to fire a spark, it uses the opposite 'maker points'. I'll be going through it over the next few weeks. CDI has a nice write-up on the system and how to trouble-shoot it.

Probably will start a new thread dedicated to the 'phase maker' . . .
 
nola mike

nola mike

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You got me interested. Seem s like it's still closer to a CDI type system than a points system electrically. This is the most in-depth explanation that I found, though the writing is a bit dramatic:

Also, you probably came across this:

1971 Mercury 7.5 Phase Maker Learnings

I thought it would be useful to post a few of my learnings on the 1971 Mercury 7.5 Thunderbolt ignition system --known as the phase maker. I've learned a ton from this site over the years and am hopeful some info I gathered might be useful to others. Background: A few of years ago I bought a...
forums.iboats.com forums.iboats.com
 
tpenfield

tpenfield

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I found that document that shows the connections, how to test, etc. My understanding is that there is a base plate (usually red in color) that has some electronics embedded into it. If those fail, it can be a show stopper.
 
tpenfield

tpenfield

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Quick update . . .

I pulled the Mercury back to my house and began to disassemble the ignition system. It probably will take a week or 2 to go through everything and make it all good.

As a stop-gap measure, I picked up this 6 HP Evinrude to use while the Merc is 'under the knife'. Some guy had it in his basement; I tested the compression (60 psi - a bit low), and the spark . . . (very good spark). Cash on the table and brought it home.
IMG_8217.jpg
The model # (6804B) maps to a 1978 model, but the cowling seems to have 1977 decals. E'rude/Johnny experts, please feel free to chime in.

Anyway, a couple squirts of starting fluid and it got going and could maintain a heart-beat on its own. I ran an intoxicating dose of fuel system cleaner and then did the Seafoam thing through the carburetor . . . The test tank filled with carbon and the motor smoothed out.

Anyway . . . I'll put this on the dinghy this weekend and see how it does in real-world conditions.
 
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