1956 7.5 fleetwin 7520 missing

[seth06]

Trying to get motor ready for the season. It will not fire on bottom plug unless rev up 1/4 past start. when rev up i can take the top plug off and it will still run but when i come back down to start or lower run for a few seconds and die. when idle it will run fine then miss for a while and go back and forth. when in trash can of water it will go to wot in gear sometimes but sometimes seems to bog down smokes really bad. Don't know if it could be coils points or maybe compression. Looked through flywheel coils look fine but i can see a green wire and red wire looks like coating is coming off. If anyone got any ideas. I would sure appreciate it. thanks also new plugs and rebuilt carb.

 

[wbeaton]

Re: 1956 7.5 fleetwin 7520 missing

You have bad coils. They need to be replaced. Do not ever run this motor at WOT in a barrel. You run a very good risk of blowing the powerhead.

 

[seth06]

Re: 1956 7.5 fleetwin 7520 missing

Would both coils be bad or just the one that doesn't fire at idle? I didn't know you could hurt the motor running it wot in can thanks.

 

[wbeaton]

Re: 1956 7.5 fleetwin 7520 missing

Sorry, I re-read your post. I thought you said the coating was coming off the coils. Replace any cracked, sweaty or discoloured coils regardless of spark condition. I still think it's your coils, though.

 

[DJ]

Re: 1956 7.5 fleetwin 7520 missing

Sorry, I re-read your post. I thought you said the coating was coming off the coils. Replace any cracked, sweaty or discoloured coils regardless of spark condition. I still think it's your coils, though.

I agree. Replace both of them otherwise you will be replacing the other within a few minutes.

 

[seth06]

Re: 1956 7.5 fleetwin 7520 missing

replaced both runs a lot better. how fast should the boat go on a 10 foot boat? the front end of the boat never would come down. the motor seemed to be running great. just don't know how it should act. I was by myself so all the weight was in the back that might be the reason just don't know.

 

[1946Zephyr]

Re: 1956 7.5 fleetwin 7520 missing

How did you suddenly come to the conclusion your coils were bad, before you fixed the wires that were losing the coating? Oh well.

 

[bktheking]

Re: 1956 7.5 fleetwin 7520 missing

Sounds to me like you still have an issue , a 7.5 should plane out a 10 ft boat without issue. Check your spark with a spark tester and make sure the spark can jump a good gap, no one mentioned points and condensors along with coils, I would have done the points and condensors first and rechecked spark.

 

[1946Zephyr]

Re: 1956 7.5 fleetwin 7520 missing

Exactly. I would have checked with the lesser expensive stuff first. Another thing to check, is the connections at the spark plug boots too.

 

[wbeaton]

Re: 1956 7.5 fleetwin 7520 missing

How did you suddenly come to the conclusion your coils were bad, before you fixed the wires that were losing the coating? Oh well.

The coil wires had lost their coating not the plug wires. Cracked coils are no good even if they spark. No sense doing anything else before replacing the coils.

I never replace the points anymore. I have yet to find a set that are worn out. I do replace condensors when they fail on my 'Steven's tester. I found that most 1950's condensor's still work, though some test weak.

A 7.5 hp should push you up to 17 mph. My best 7.5 hp pushes my 12' boat 13.7 mph or 22 kmh.

 

[seth06]

Re: 1956 7.5 fleetwin 7520 missing

so should 17 mph make boat level out with 1 person about 185 plus 4 gal. of gas and battery all in the back of the boat. I couldn't tell but i thought i was doing about 10. not sure hard to tell on the water. Even though boat didn't level it road smooth.

 

[wbeaton]

Re: 1956 7.5 fleetwin 7520 missing

My 12' boat planes around 10 mph or more precisely just over 15 kmh. You may still have a problem. Might be the used coils you used or something else. We need more information. Have you cleaned and gapped the points? Did you replace the plug wires or reuse them? If you reused them did you trim back the old wire to make the new connection at the coil? Are you getting spark at both plugs and how big is it? What is the compression on both cylinders? All the old original coils go bad with age. Attached is a set of original coils from a 1972 Johnson 6 hp.

The problem may also be how you have the boat set up. Try moving the gas tank to the bow and try different settings on the trim pin.