1971 55 hp Chrysler Quits When Warm

[Fabuglas]

Last season my 1971 55hp Chrysler outboard ran poorly after a solid hour or two of running. I found a cracked coil. I replaced both coils, both spark wires, both plugs, both sets of points and two new condensers. It ran like a champ all last season after installing these new ignition parts. Recently the motor quits running after it has been used for an hour or two. It runs without any indication of a problem and then suddenly acts as though it has bad fuel. When the motor quits it will not start and run on its own unless I physically hold the choke almost closed. With the choke modulated by hand, I can get it to start and run but not to full rpm or power. This tells me it is unlikely an electrical problem. I am sure the fuel being burned is good. After cooling down for an hour, the motor will run like new again. I suppose it's possible one of my new coils could be acting up when it gets warm as nothing says new coils can't fail after just 10-12 hours of life. I am wondering if any of you familiar with these outboards think it could be the fuel pump or something else I have not considered? Is it possible for an old fuel pump to work just fine after rest, or when cold, and become fatigued after cycling or getting warm no longer delivering proper fuel?
Any experienced help is greatly appreciated.

 

[gm280]

Fabuglas, I am not so sure it is electrical at this point. The fact that you have to "modulate" the choke doesn't sound electrical. But we will see. When your engine just starts to act up, have you tried to remove any one of the spark plug boots to determine if it is one cylinder or not? That could offer more insight to the issue. Also have you tried to squeeze the primer bulb to see if it is a fuel delivery issue? Squeeze the primer bulb when it starts acting up and see if that makes any difference. Post those results. JMHO

 

[Fabuglas]

I agree it is likely not electrical. I did try squeezing the fuel bulb from the tank while the motor was running manually choked, thinking this may override the fuel delivery from the fuel pump and deliver sufficient fuel if the pump was starving the motor, squeezing the bulb made no difference. That said, if you have to choke the motor to keep it running, does that not suggest too much fuel not, too little?

 

[Fabuglas]

Sorry, your question regarding spark. The motor will start and run manually choked. while running in this fashion I have both cylinders firing. This leads me to believe it is not electrical.

 

[Nordin]

When it starts to acting up after 1-2 hours running, have you run it at higher rpms or cruising at idle?

Check the plugs when it quits. Are they wet or dry? If wet maybe to rich mixture or fouled by long idling.
If dry maybe fuel delivering issue.

Also check the impeller. Is it cooling properly?

 

[Fabuglas]

The last time it quit it was after idleing for a while up a river in No Wake zone. It was run hard across harbor before entering river. We paddled over to a dock. We thought it was bad fuel so we drained carb and float bowl and hooked up new fuel source. This took about an hour. Then it started and ran fine. Left the dock slow no wake for a mile or two. Then wide open across harbor. All was fine for about 5 minutes at WOT then it shut down and would not start. I towed it in and haven't look at it since.

 

[jerryjerry05]

Sounds like it's running HOT!!
​Test the alarm?
On the head is the sensor.
Ground it out while the key is on.
It should make the buzzer sound off.
Any car/ motorcycle horn should work.
Just make sure the leads are hooked up right.
They can be hooked up backwards and not work.

 

[Fabuglas]

All, Thank you for your input. It seems that no one is buying into my fuel pump theory. I Think Jerry makes a good point that it may be getting hot. I don't believe anyone has checked that. Easy enough to check out. I have never put a water pump in it so, regardless it's something I should do. I'll plan on checking that out this weekend. Any favorite sources for a water pump kit for this motor?

 

[jerryjerry05]

They sell the impeller here.
​I use e-bay or a local store if I'm in a hurry.

 

[wickware]

Add a Tell Tale to see a solid water output vs water mixed with exhaust. Deep in a barrel has been my best test vs muffs. 2? too high in a barrel caused no ?Instant water? in one case..

Search wickware to see much more on years of service on this motor.

That is very close to my 1970 35 HP Chrysler (with a 55 hood showing). That is said to be the same as a 55 HP Chrysler without long lower unit leg and 2 Carbs (with more piston bore and Etc). I am seeing external coils vs my under the flywheel coils...

 

[wickware]

No Title

1. I almost cracked a coil from running a bolt too deep pulling the flywheel (showing attached).
2. An in-line cheap spark tester might tell you something related to firing good or bad.
3. Have you inspected and cleaned if needed and adjusted your points to .020 or as instructed?
4. Do you get instant cooling water when you start? The Tale Tell shows solid cooling water.
5. Do you have past/present experience on this motor or have a close friend? They are friendly!!!
6. My 1970 35hp and your 55hp could be the same except piston, bore and stroke.

See the attachments:
Good Luck!

 

[Fabuglas]

Water pumps fine. Suggests it is not an overheating problem. Motor will start right up when cold and fast idle for approx 5-10 seconds before acting like it runs out of fuel. May be dry top crank seal allowing air in. I will check for that later this week.