55hp Chrysler back firing

[artw45]

Bought the boat and motor a couple of weeks ago. Condition of motor unknown. Model # 555HE serial # 5126. Not sure about the yr, trying to track that down still. Replaced the fuel line, squeeze bulb, connectors ect. Put fresh gas to it and pressurrized the system. After a little mesing around with a few things. Got it to turn over. Started right up and I shut it off to go turn the water back on. (Had it off while I was working at getting power to the starter.) Got the water turned and and tried it again, started up very quick and sounded great. Then by the time I walked to the back of the boat it died and won't do anything but back fire. Compresstion seems to be good, but am planning to check it as soon as it quits raining long enough and I have time. Any ideas as to what would make this happen? Bad coil or condenser? Broken flywheel keyway? Any help would be great. <br />Art

 

[chuckz]

Re: 55hp Chrysler back firing

Did you mix oil with the gas?

 

[scotiany]

Re: 55hp Chrysler back firing

The 1st place I'd look is under the flywheel. Sounds like a busted flywheel key. They are available at Mercury dealers. Quicksilver PN 28-F92498. An undertorqued flywheel nut will cause this.

 

[eurolarva]

Re: 55hp Chrysler back firing

It looks like your motor is a 1973. Is the backfire coming from the carburator or out the exhaust?

 

[artw45]

Re: 55hp Chrysler back firing

First off I did mix the gas! But a valid question, they burn up quick if you don't. Thank you for the imformation on the yr. That is very useful. The boat is a 1970, and this model seems to have come out in 1970, so I was assuming it was a 1970. I'm going to check the flywheel. I appreciate the help. I have a 79 45hp chrysler I've had for 3 yrs and haven't had a problem with it. Chryslers are getting to be a favorite of mine. Hope I can supply some answers of my own some day!<br />Art

 

[artw45]

Re: 55hp Chrysler back firing

The backfire is coming from the exhaust.<br />Art

 

[chuckz]

Re: 55hp Chrysler back firing

Before you start pulling things apart check the static timing. Bring #1 up to TDC and see if the timing marks on the flywheel line up. This will give you a quick indication if you have a mechanical problem.

 

[artw45]

Re: 55hp Chrysler back firing

The key was broken, the points look real good. Almost no burning at all on them. Didn't look to me to be the right flywheel nut. Was a nylon locknut. And the coils are on the breaker points base under the flywheel. From the dyagrams in my manuel I'm fairly sure this is a magneto ignition?<br />Art