1975 johnson 85 hp, wont fire

[phlawjer]

i just recently bought a 1975 johnson 85 hp. when i bought it, we started with muffs, it was cold and took like 10 minutes but it ran fine. when i got it home and in the water it wouldnt start. it would turn over and over and wear the battery completely dead. all 4 coils are cracked bad 2 have wax or something in the cracks. could this make it not fire? if so why did it start the week before? please help... thank you

[crb478]

If the coils are cracked they are bad or they will be. You may be able to epoxy over the cracks after baking the coils in the sun and getting the mositure out and get a little more life out of them. I have seen several done this way, but new coils would be better. If you still have the green coils they are probably the origionals and due to be replaced anyway. Get a spark tester and test for spark for each coil. Look in the frequently asked questoins on awakening a sleeping outboard and you should find lots of good information. Before you spend any money test the compression on all 4 cylinders. Over a hundred and with in 10 percent of each other is what you are looking for.

[HighTrim]

Welcome to iboats.

The reason it ran fine at first was because you were on muffs, and there was no backpressure on the exhaust. You cannot trust the way an outboard runs on muffs. When you present backpressure, things change.

As stated, I would start with a spark and compression test and go from there.

These inline spark testers are readily available. The spark should jump a good 7/16 of an inch with a strong blue ZAP!!

spark tester.jpg

Outboard Wont Start, from the FAQ

http://forums.iboats.com/engine-frequently-asked-questions-faq/outboard-wont-start-158071.html

[ezeke]

Before anything else, the ignition on your motor will not fire cold without a fully charged powerful battery. It must crank the engine at 300 RPM to work. I use 650 CCA or better dual purpose deep cycle batteries.

When starting cold, use full choke until it fires.

Don't waste time on the coils; replace them. The new ones are much better.

[phlawjer]

ok i replaced all the coils and boat starts awesome runs awesome with muffs but when i got it in the water it wouldnt throttle up and it would die when i tried to put it in gear and go. so i checked the compression with tester and they all read 45... is this bad if so what should i do? thanks guys i really appreciate it

[crb478]

ok i replaced all the coils and boat starts awesome runs awesome with muffs but when i got it in the water it wouldnt throttle up and it would die when i tried to put it in gear and go. so i checked the compression with tester and they all read 45... is this bad if so what should i do? thanks guys i really appreciate it

If the compression tester is reading correctly that is low compression. I would be suspect of the tester since they all read 45 it seems like it might be sticking at 45 you may want to try it in another engine to see if it also registers 45. Have you done a link and sink? When were your carbs last rebuilt? If it is now cranking easily I suspect it is now a fuel type issue.

[F_R]

It would be surprising if it ran at all with only 45 psi compression. Are you letting it turn over enough times to get maximum reading? Either your motor is BAD, bad or the tester is.

[ezeke]

Sounds like you may need to either rebuild your carburetors if they have not been done lately AND/OR, you need to synchronize them.

Take the cover off the carburetors, and verify that 1. all the choke plates are fully open (horizontal) and synchronized, when you have the engine warmed up, 2. that the throttle plates are working together and fully horizontal at WOT (fully advanced throttle. 3. That the spark advance is connected at the top of the throttle lever.

What spark plugs and gap are you using?