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jd39819

175 johnson faststrike

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I have a 1992 Johnson 175 fast strike.  I just put a power pack on last night and it runs fine except when you get down on the hot foot it skips.  I stopped for a second then it ran fine.  I stopped gain then took off and it started skipping again.  What could my problem be and input is greatly appreciated!

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First off, you probably should install a new set of plugs if you haven't done so recently.  Then you should try to determine which cylinder/cylinders are skipping.   Without a dino or test prop, the best way to do that is to do a plug dump.  Hold the hot foot down for about 30 seconds or so while it's skipping and then turn the switch while still holding it down (understand, this is going down the lake, not in your yard).   Now, remove the spark plugs and see which ones are wet/dark.  Do not restart the motor until you have looked at the plugs

Once you have determined which cylinders are skipping, swap the coils and plug wires and do another plug dump.  If the problem moved to the cylinders that were good, then you can figure you have a bad coil/plug wire.  If the same cylinder is still the one skipping, then you have a problem that might be beyond your level of repair.  

 You will most likely need DVA or Peak to Peak Voltmeter (this is not your standard DVM) or an O-Scope, and a good service manual is also a must have.  

If that motor has the shift interrupt switch on the side of the shift linkage (under the engine cover) those can mess up so unplug it if it will let you just to try it.

There are a couple of coils on the Stator that can cause problems

The timer base is what generates the initial spark signal and sends it to the power pack.  The disc or pickup may be causing problems,  The new power pack can also be the problem.    A weak magnet in the flywheel can cause problems

When you get into ignition problems and don't have a dino or test prop, things can get very complicated and difficult to troubleshoot.

To add to all this, you have to determine if it's ignition  or fuel causing the misfire.  Could just be carb or other fuel problem, so you don't realty want to shot gun parts at it because there is nothing cheap about any of them. 

One other tidbit, the block could be cracked and letting water leak into on the top cylinders and causing a misfire.  The Fast Strikes have a casting flaw that probably 75% of them crack where the Rectifier bolts on and lets water into the cylinder, which can also melt a piston. 

I also haven't worked on Fast Strikes so can't get real detailed in being able to tell you exactly how to check each part.

 

 

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I had been running fine until this weekend and the thermostat cover worked its way out and lost it.  The boat still ran good I just know it was shooting water every where until we got back to the landing.  Im sure that's what caused my power pack to go bad!

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On 6/25/2016 at 6:44 AM, jd39819 said:

I had been running fine until this weekend and the thermostat cover worked its way out and lost it.  The boat still ran good I just know it was shooting water every where until we got back to the landing.  Im sure that's what caused my power pack to go bad!

I used to have a 175 FastStrike as well.  Great motor. 

If you don't have the 300+ page service manual for your motor, I'd recommend spending the 8$ for the PDF and printing it out. Saves you a lot of headaches. I think I still have mine but it was for a 1991. Might be the same manual. If it is, let me know and I'll just e-mail you mine. I've got a 2016 merc 150 4 stroke now so I don't need mine.

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THANKS

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3 minutes ago, jd39819 said:

THANKS

No problem bud. PM me if you need the manual. 

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