hp70 1980 backfire won't start now

[RJDAWSON]

We put the 70 hp1980 in the water the other day and started right off. It ran for about 2 min. and died, Fired and up and ran for another 2 min, but won't start now. Found a bad rectifier with ohm's test, and replaced it, stater measured good on ohms test, but the sensor coil resistance test was just short of the 17 +/- 5. The best reading 11.93 falls just shy of the 17 mark. Is this close enough or do I replace it now? I had good spark, jumping 1/2 inch, I've cleaned the carbs. With fresh fuel I'm get intermittant pop's of back fire. I'm on vacation but have some tools. I am not able to do any output tests, an should I see about finding an OMC CD Tester, to do out put tests, as it seems that most of my troubles have been electrical.

 

[Sixmark]

Re: hp70 1980 backfire won't start now

The minimum is the minimum, and if your BEST reading falls below the minimum then don't even take the chance, unless of course you want it to fail completely while you are out on the water.

 

[DJ]

Re: hp70 1980 backfire won't start now

You stated "Backfire" in your post title.

While rare, if the backfire was violent, you may have sheared a flywheel key.

 

[boobie]

Re: hp70 1980 backfire won't start now

DJ beat me to it, but I was going to say the same thing about a sheared flywheel key.

 

[RJDAWSON]

Re: hp70 1980 backfire won't start now

Good points all. I have sheared a fly wheel key before. I will check it and yes being caught out on the water with out a putter would be bad.
Thanks

 

[RJDAWSON]

Re: hp70 1980 backfire won't start now

To up date my post: while starting up the motor it did back fire. I did find a bad rectifire which may have caused the back fire and sheared the woodriff key. The key has now been replaced as well as the rectifire and the motor started on the 2nd turn of the key.
One note; I talked to a Johnson/Evenrude mechianic, he offered that shearing the
woodriff key may be due to not having the nut on the flywheel tight enough. I have had it happen before.
Thanks for the input from all.