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Help on 1971 Chrysler 55HP Outboard

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Help on 1971 Chrysler 55HP Outboard

Old 04-19-2020, 10:11 PM
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Question Help on 1971 Chrysler 55HP Outboard

Hello all, my friends and I have been working on a project boat that we got for free for the past 7 months. I got to the engine and have been having trouble getting it running, its spitting in the exhaust almost as if the combustion is happening in the exhaust, not cylinders. We thought it was lean sneezing at first so I enriched the throttle screw which caused no combustion, and starter fluid as I started to give up hope. I knew nothing about engine's but have learned so much in the past 2 months. I now think that the timing is off but don't want to go too far down the wrong rabbit hole. Any clues on what the problem could be?
  • Changed lower unit gear oil, very small amount of water was inside (uh oh), the previous owner had it in a bucket of water for 5 months idky, but I checked after a couple tests and there was no water in oil, fingers crossed
  • Replaced Impeller
  • Checked Compression, 140 top, 130 bottom, manual recs 135-165.
  • New sparks, but gap was off from original by 0.002 in
  • Cleaned carb the best I could, inlet needle functions
  • Most of the fuel lines are so stiff we couldn't get them off, but from the appearance of the gas that was in the fuel bowl it didn't have debris
  • Cleaned fuel bowl, made the height what manual stated
  • Wires all in Place
Notes on Motor
  • Piston Heads look like they have carbon buildup, but has greenish buildup in some spots.
  • When I put a new starter in it and started it up for the first time there was a small amount of white smoke that came from flywheel but we played it off as the burning of cobwebs.
  • The previous owner claims to have replaced the head gasket, but we haven't checked yet
Tests Summary: Multiple times we try to start it and you can hear the combustion process going through but the exhaust is spitting heavily, and gets close to start but then stops, holding it at full choke and throttle as that was the only way to get results.
Old 04-19-2020, 10:15 PM
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I posted a compilation of our attempts from March on YouTube, videos called: 1971 Chrysler 55HP Help Comp.
Old 04-19-2020, 10:36 PM
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If you really want some help with it make this post on FiberGlassics® - Index - FiberGlassics® Forums They deal exclusively with old boats and motors. I've seen these old Chrysler engines talked about frequently
They even have a separate forum for Chrysler Engines.
Old 04-19-2020, 10:39 PM
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Possible Water getting in cylinder
Old 04-19-2020, 10:49 PM
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Almost everything you mentioned, except the smoke from under the flywheel mean nothing, smoke from under the flywheel is a killer and needs investigation.
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Old 04-19-2020, 11:59 PM
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I'd pull the plugs , reinstall the cable boots on them and ground the plug threads to a bare spot on the block while cranking to check for bright blue spark .
Then I'd want to remove the flywheel and check the points and condenser(s) There may be 2 of each.
There probably is a linkage going from the throttle arm up under the flywheel to advance the timing. Noting exactly where is was to begin with you might very briefly try manually moving it to see if it makes any difference in combustion smoothness.

Also I'd check the old plug cables for any cracks that might be allowing shorting to the block, and since you mentioned the fuel hoses were very hard, look for any suction air leaks there. Check the condition of the coil (any cracks?)

Does combustion improve at all if you squeeze the primer bulb?
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Old 04-20-2020, 01:40 AM
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You may want to pull the flywheel and check the key, magnets and condition of electrical components.
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Old 04-20-2020, 04:22 AM
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Originally Posted by SeaCat22 View Post
You may want to pull the flywheel and check the key, magnets and condition of electrical components.
I came here to post this. many moons ago i had an old Chrysler on a McKee craft. It sheared the key a few times no fun.
Old 04-20-2020, 05:16 AM
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My dad had an old 18HP Johnson that kept sheering the key. One solution was to use an aluminum beer can and make a shim that fits between the shaft and the flywheel. Other products like Quick Metal or LocTite offerings also can help.

I agree with other posts. Pull the flywheel and check everything underneath.
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Old 05-14-2020, 01:18 PM
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Ok, so I finally got the flywheel off and the key was sheared and one of the coils was cracked really bad and one of the cracks had a small amount of melted metal coming out. The ignition system is a Magneto the coil's model number is F12057. I have found a replacement key but the OEM coils are used $120. Would a new Sierra 5181 Coil work just as well? Its much cheaper. Also do I have to set timing once i get new key? And is there anything else I should replace?

Old 05-14-2020, 08:51 PM
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Shouldn't need to be timed again. When I've had a flywheel key shear I'd take some valve lapping compound on the shaft, rotate the flywheel with putting pressure down on it, clean everything well, install new key, and the reinstall flywheel and torque nut to specs. By lapping the flywheel down (after it's spun) it will seat better.
Old 05-15-2020, 12:40 AM
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If the Sierra coil is the same, it should work fine. If you didn't mess with it, the timing should be close enough to start it. Let's see a video of it running. I had a Chrysler many years ago. Simple engine.
Old 05-15-2020, 07:06 AM
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''
Old 06-18-2020, 09:22 PM
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We got the new coil a week ago and installed it with new key. We're getting ignition in the cylinder that was already firing. However the cylinder with the new coil is getting no spark. I cleaned the points but they aren't 100% flush with each other, more like 60-80%, but are really clean and spaced to spec, new condenser, kill switch wire works, and I made sure the coil lamination and its ground were clean. We ran tests with a multi meter following some guides and everything checked out, even when we ran it we were getting an increase in dc voltage readings when attempting to start. Does anyone have any suggestions?
Old 06-19-2020, 04:31 AM
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Originally Posted by boatingboy1 View Post
We got the new coil a week ago and installed it with new key. We're getting ignition in the cylinder that was already firing. However the cylinder with the new coil is getting no spark. I cleaned the points but they aren't 100% flush with each other, more like 60-80%, but are really clean and spaced to spec, new condenser, kill switch wire works, and I made sure the coil lamination and its ground were clean. We ran tests with a multi meter following some guides and everything checked out, even when we ran it we were getting an increase in dc voltage readings when attempting to start. Does anyone have any suggestions?
Switch out the coils to see if you get spark on the bad wire.
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Old 06-19-2020, 05:00 AM
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Give you a lot of credit for tackling a very old outboard, most people would have made it a anchor. Was this outboard used in freshwater or salt?
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Old 06-19-2020, 02:53 PM
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I'm assuming freshwater because the previous owner that gave up on fixing the boat it came with got it from Traverse City, Michigan.
Old 07-09-2020, 10:57 PM
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Just wanted to give an update, we got the motor running! After ten months of working on it my high school friends and I got it to work and it starts right up really well. We replaced the Magneto and it still wouldn't work, we rebuilt the ignition system 4 times and we needed to get new points and reuse an older condenser. We put it on a 71 Comoro 16T and had a lot of fun on the water even though it only goes 6-8mph with 4 guys, it reaches 20mph with only one person on the boat.
Now that the motor is running I have two questions
-We don't have a trim motor or device so for maximum speed and longevity of the motor what trim would be best to set it at?
-Should we be worried about overheating the engine? The temperature sensor doesn't work anymore so I can't see, but the tell-tale has good water flow coming out of it and we ran it today and it ran perfectly even though the water gets pretty hot at idle .

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