1974 chrysler 55HP wont stay running.

I have a 1974 chrysler 55 HP magnapower 1 model 554HA.I had it running tuesday in a tub of water ran great at idle and when motor was engaged. it has been kept in a garage ever since. I went to start it today in a tub of water it didnt want to fire over just crank then back fire then we flipped the spark plug wires it would fire and run for about 15-20 seconds then backfire, sometimes continue running others just kill out. Does anyone know what it could be? The starter and soleniod are both brand new installed tuesday. And what spark plugs should be in? Autolite 4113 were pulled out and was told no one can get them I was told AC Delco plug r45t were the same put them in wouldnt fire put a set of plugs from my old ford that were brand new in and it would still backfire and cut out sometimes continue to run. can anyone help? And the battery is garbage using jump starter to start it through batter cause it wont hold a charge. could that be the problem?
After going back through reading older posts making sure this wasnt asked before.
Plugs get spark
Motor turns over
not sure of gap on plugs or points.
note sure of compression
gas mix is 50:1

Re: 1974 chrysler 55HP wont stay running.

Check the fuel pump diaphragm, or better yet just get a rebuild kit for the fuel pump as a matter of maintenance. Check your fuel lines too and replace as needed. Could be several issues but I'd start with simple/easy first. Good luck...

Re: 1974 chrysler 55HP wont stay running.

huskerdaninva said:

Check the fuel pump diaphragm, or better yet just get a rebuild kit for the fuel pump as a matter of maintenance. Check your fuel lines too and replace as needed. Could be several issues but I'd start with simple/easy first. Good luck...

Click to expand...

all the gas lines are new I forgot to mention that they were installed tuesday... I am going to try to swap parts from my parts motor to this one an see hwo that works out for me

Re: 1974 chrysler 55HP wont stay running.

Magna-Power electronic igniton requires Champion L20V, UL18V or NGK BUHW. These are surface gap plugs and gap is set at factory. Do not use a bent electrode plug. When you do get it to run there is a real danger of melting pistons with them.

Top coil is top cylinder and bottom is #2.

Backfiring is a symptom of fuel problems. Are you choking it to start? If not, it will crank, fire, and stall all the time. You must also open the throttle just a crack--If controls are attached, you pull out the silver knob and set the control handle as far forward as it will go. This is cold start/fast idle position. If this doesn't help, remove the carb or carbs and clean them. Search previous posts for carb settings

Re: 1974 chrysler 55HP wont stay running.

Ok thanks Frank. I have choked and not choked both did same thing did the cold idle deal seemed to run better when I didnt use the fast idle. I have that spare motor I will tear the carb off and clean and rebuild that and see how she goes. Hopefully it will fix it. Oh and does the fuel line length matter? I have alot of extra line in the boat the tank i can probably reach the seats with how much line i have. It is the same as when it ran tuesday though. Could the carbs have sucked something in from the tank? I know very bad idea to run without fuel filter my inline glass filter broke and didnt get a new one.

Re: 1974 chrysler 55HP wont stay running.

Oh and Frank what would be better Mallory or Sierra for the carb kit

Re: 1974 chrysler 55HP wont stay running.

I have a fuel line that is almost 8 feet long in one of my boats. It still delivers well. length should not matter that much. And yes, you may have sucked in some crap. Go to the local auto store and buy a cheap plastic inline filter anywhere from 3-6 bucks.

As far as mallory or sierra, I have no opinion. I have ordered parts and gaskets from iboats and ordered mallory (i think) because they were a bit cheaper and seemed to be the same.

Re: 1974 chrysler 55HP wont stay running.

Wel lI found the problem the bottom coil wire to plug was garbage the guy who owned it before me must have been real cheap he broke the prong off the wire and tryed to rig it to work so it wouldnt get spark now and then causing the backfire and not running