1994 Johnson Fast Strike 150 dies when it warms up

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Baxter83

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The title says it all as for the problem. I crank it, it fires right up (on muffs and in the lake), it will blast off, but only until it's warm then it bogs down and eventually dies. Then it won't even fire back up until hours later after it's cooled off again. The same thing happens on muffs except there's no blasting off involved...lol

History of the engine since I've owned it: I had it rebuilt upon purchase as the # 2 piston had a golf ball sized hole in it due to the previous owner running with no oil (the oil line nipple inside the cowling broke and it wasn't getting oil). After receiving it back from that shop it didn't run well after a short while and long story short, mostly for those familiar with this generation of the 60 degree Johnsons, it had a crack in the glue line behind cylinder # 2 exhaust, so I had to tear it back down and get it welded up, 2 cylinders re-machined and sleeved, and I reassembled it at home. I disconnected and capped off the oil injection and have premixed since I've owned it, and it ran flawlessly for 2 years, and now this. I'm stumped.

Here's what I've done so far:
compression test - good
spark test - good on all 6 (gap tested at 7/16")
new impeller and seals (good water flow)
new thermostats
new vapor pump diaphragm
new primer solenoid gasket
checked flow through water path to thermostats - no obstructions
checked water flow from thermostat down through head passages - no obstructions
checked temperature switches - good (even disconnected to fully isolate)
disconnected alarm wire from VRO to isolate fuel flow alarm (no change)

I'm thinking that it's a fuel problem, but have no clue where to go from here.
 
dingbat

dingbat

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Electronics are notorious for breaking down when heat stressed then return to “normal” once cooled.

Ignition coils and stators are infamous for this behavior.

See lots of things changed but nothing checked.

Have all the electrical components been fully tested? Stator, rectifier, etc.

Could very well be a diode in the rectifier breaking down under load.

Do you have any spark when it shuts down?
 
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Baxter83

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dingbat said:
Electronics are notorious for breaking down when heat stressed then return to “normal” once cooled.

Ignition coils and stators are infamous for this behavior.

See lots of things changed but nothing checked.

Have all the electrical components been fully tested? Stator, rectifier, etc.

Could very well be a diode in the rectifier breaking down under load.

Do you have any spark when it shuts down?
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Yes sir. I agree.

I ohmed coils cold and hot, and they should be fine. I can't recall the resistance reading that I was getting, but remember that it was within .002 of being identical across all 6. This is why I've been through two new power packs thinking that the pack was bad and coils are good.

I have not tested the stator because my theory is that I'm getting a good spark even when it starts acting up, so it should be good.

New rectifier, but I understand that even new parts aren't always perfect.
I have a service manual, and it is probably in there, but is there a procedure or method to testing the rectifier and stator?

When it shuts down it isn't an immediate shut down. There's a noticeable change in idle from the normal idle rumble to like a pop pop pop pop pop pop for a minute or two, which at this time is when there's little to no power, then it gradually slows down to fully shut down. Make sense? It does have spark on all 6 cylinders until the point where it can't due to no more rotation.

Something else that I left out. I've tested the shift switch and it's good. Probably could've left that out as I've already stated that I'm getting fire on both banks while it's acting up, but it can be scratched...I think.
 
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dingbat

dingbat

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Baxter83 said:
I ohmed coils cold and hot, and they should be fine. I can't recall the resistance reading that I was getting, but remember that it was within .002 of being identical across all 6.
Click to expand...
Ohm testing does nothing but confirm a coil has failed or not failed outright. It does not tell you anything about how the coil is performing under load.
Doubt this is your problem considering all are "breaking down" at the same time which is lightly unlikely.
Baxter83 said:
I have not tested the stator because my theory is that I'm getting a good spark even when it starts acting up, so it should be good.
Click to expand...
#1 rule of troubleshooting.... don't assume anything. The stator supplies the voltage to the entire ignition system. A problem here will trickle down through the entire ignition system.
Why did you replace the power pack for a second time?

How did you confirm your getting good spark continuously to all 6 plugs while it's acting up? The acting up could be individual cylinders dropping as the system starts to loose power. Not going to see that with a conventional spark tester. Need a Xmas tree setup.

Baxter83 said:
New rectifier, but I understand that even new parts aren't always perfect.
I have a service manual, and it is probably in there, but is there a procedure or method to testing the rectifier and stator?
Click to expand...
The OEM manual gives detailed test procedures for all electrical components in the system. I would suggest starting with the Stator and working your way though the system from there
Baxter83 said:
When it shuts down it isn't an immediate shut down. There's a noticeable change in idle from the normal idle rumble to like a pop pop pop pop pop pop for a minute or two, which at this time is when there's little to no power, then it gradually slows down to fully shut down. Make sense? It does have spark on all 6 cylinders until the point where it can't due to no more rotation.
Click to expand...
Exactly what I would suspect as a component breaks down in the system under load.
Pop, pop, pop, could very well be intermittent misses caused by a slow deterioration of voltage and or current over time.

Which came first? The chicken (failing stator) or the egg (engine stopped rotating)?

Sorry I can't help more but your 150 Hp uses a little different ignition system than my 200 Hp
 
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Baxter83

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dingbat said:
Ohm testing does nothing but confirm a coil has failed or not failed outright. It does not tell you anything about how the coil is performing under load.
Doubt this is your problem considering all are "breaking down" at the same time which is lightly unlikely.

#1 rule of troubleshooting.... don't assume anything. The stator supplies the voltage to the entire ignition system. A problem here will trickle down through the entire ignition system.
Why did you replace the power pack for a second time?

How did you confirm your getting good spark continuously to all 6 plugs while it's acting up? The acting up could be individual cylinders dropping as the system starts to loose power. Not going to see that with a conventional spark tester. Need a Xmas tree setup.


The OEM manual gives detailed test procedures for all electrical components in the system. I would suggest starting with the Stator and working your way though the system from there

Exactly what I would suspect as a component breaks down in the system under load.
Pop, pop, pop, could very well be intermittent misses caused by a slow deterioration of voltage and or current over time.

Which came first? The chicken (failing stator) or the egg (engine stopped rotating)?

Sorry I can't help more but your 150 Hp uses a little different ignition system than my 200 Hp
Click to expand...

Awesome feedback. I think I need to get back to the basics.

I replaced it the 2nd time because the 1st time I replaced it based on information from a seasoned Johnson mechanic and it cleared up for 6 or 7 trips. I thought I got a cheap part that went out. Basically just throwing parts at it which is why I’m humbling myself and reaching out for y’all to help me more logically troubleshoot.
 
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Baxter83

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So, for anyone interested, I was finally able to carve out a few minutes to poke at my engine last night and found that there were multiple bolts that had worked loose on the stbd side intake manifold. One actually backed all the way out and the other two were ~hand tight. I busted all of the stbd side carbs off and checked gaskets and whatnot, did a quick visual of the reeds, and then torqued everything back down. I plan to do the same for the port side and then check it out again after that. Maybe a smoking gun?

If I could use a vacation day to stay home without getting roped into the obligatory "honey-do's" I'd take it so that I'd have time to work on this thing and get it going...
 
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Baxter83

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I haven't followed up on this post in a while, mainly because I still haven't figured it out, and also because I have embarrassingly overlooked some obvious stuff. Apparently after waiting for it to "cool down" for a good while I would naturally pump the bulb to prime the system again out of habit, so it would run good again. So, since the last post I have done the following...

1) Determined that it is a fuel delivery issue because pumping the bulb when it starts to change tone at idle prior to dying altogether will recover it and it will come back to a good idle again until it runs back out of fuel in the system... (muff testing, not on water). Apparently I just had to put more effort into pumping the bulb than I was prior to eliminating that as a possible cause... :/
2) Rebuilt the fuel pump with all new seals and diaphragm as well as thoroughly inspected the housing for cracks. It is pumping good, and I think it probably was before as this didn't correct the issue...
3) Replaced the entire fuel line from the pickup tube in the tank all the way to the cowling as well as a new bulb, and made sure the vent valve at the tank worked well. Still have the issue...
4) Rebuilt all of the carbs and corrected any warping in the bowls. Also found a few of the little pressed in ball bearing things in the bowls were leaking and fixed that. Still have the issue...

So as of now I only have the primer and vapor separator left to examine more thoroughly and/or rebuild. I have already had all of the fuel lines off and inspected them, and they're good.

Question: Now that I know that it is dying due to fuel starvation and knowing what all I have changed out, does anybody have prior experience with vapor separator or primer solenoid problems that has caused this?
 
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Baxter83

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FreeBeeTony said:
Did you fix you're issue? I have a similar problem.......
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Yes! I followed up on a different site, but forgot to here. So I ended up discovering that the Powerhead was replaced with a newer one prior to me getting it. Although I had it rebuilt and have bought parts based on the model number on the transom it was all stuff that happened to match up. The difference was how the tubing for the vapor pump hooked up and to where. After all that I swapped a couple of hoses around and all is well.
 
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