1999 Johnson 90hp lost partial power after trimming too high

[Rom6100]

Update from the water today. I swapped both the coils spots today, so I unplugged all spark plug wires and the other 4 connections, some of the smaller connections had crusty gunk inside, I ran the boat on the water with no issues. Idle I was running 12.4-12.7 volts, throttle 13.5-7. The lake close by is small so I did about 7 runs up and down, shutting the motor off each time. It didn’t lose any power or cylinder, granted it was a short 45 minute session. I’m hoping it was just some gunk that stopped the circuit. Now on to the tach. Still getting inaccurate readings. The ground appears fine but I am going to try and pop it would to get a better look. The whole tach has a harness with about 8 wires as it has all the sensors built in oil, temp, check engine etc.

 

[Rom6100]

Update on the tach. I disconnected the harness and one if the pins inside had slipped out of spot, I reset it to where it should be and now it’s good. Just an FYI if anyone has jumpy intermittent tach check that harness

 

[He rik]

Good!

Always look at the easy and cheap solution first.

And, thanks for updating with the solution, may help next who search with similar probs.

 

[Rom6100]

Another update, the boat now is back to the same problems it was before, loss of power and hesitation, new issue is the bolts are spiking to 15.5-16.5 which is way too high. I didn’t have any tools on the boat to wiggle anything around this time so it was a pretty big waste of a day. Drove to a larger lake. Any ideas on the high volts?

 

[Rom6100]

Went out after I got some tools and volts not getting higher then 12.3 which is just battery voltage. Tach working fine, I swapped plug wires and can say it’s one cylinder that is misfiring. The problem didn’t follow the plug wire or the coil. So where can I begin to diagnose the misfire on one specific cylinder?

 

[Chris1956]

How about the carb for that cylinder? Is the bowl warped? Does fuel come out when the brass screw at the base of the bowl is removed? Is the throttle plate opening when the throttle moves?

 

[Rom6100]

There’s a lot of stuff in the way of the carbs, in going to look into it later. I feel it’s electrical though cause of the voltage issues, today I tried to run it with the rectifier plug unplugged. Same issues. I found that if I plug and unplug spark plug wires it sometimes makes a diffeeence. I ordered a set of those on the way and ordered a power pack to see that is the problem. If it is spark plug wires, it wouldn’t make sense the voltage fluctuations though. We’ll see what the new parts do on Wednesday.

 

[Wrekked]

Wouldn't make sense for the one cylinder misfiring as I would expect it to effect all cylinders randomly, but for the voltage spikes, could be the voltage regulator in the alternator is toast.

 

[oldboat1]

You haven't posted a model number, but that motor likely came with a water-cooled 20amp regulator/rectifier. Running in the lake should be safe enough if your water pump impeller is working right. But you can be literally playing with fire with that unit -- as in smoke and flames. A high charge rate could be due to an undercharged or defective battery.

 

[Rom6100]

[h=2]J90PLEEB is the model, I also dont think I’m getting the same cylinder misfire all the time. I took out the plug cylinder that was misfiring prior today and ended up on 2 cylinders where it wouldn’t push the boat well at all. Atleast on 3 it moves the boat. It does seem like the misfire moves around. I thibk that is why I am chasing my tail trying to determine which one it is and when I think I have it it moves. I have additional cranking batteries I can swap and try. The high volts only happened once then it went back to just 12.3. One day it was volts we’re correct and everything was running well with no misfires. The next day, misfires with inconsistent cylinders. The pee hole for the impeller throws lots of water. The rectifier is right on the top as its own separate electronic unit. There isn’t any water flowing through it. Perhaps underneath but following the CID instructions I disconnected the yellow wires and still have the miss going.[/h]

 

[Rom6100]

And another update. Swapped out the power pack and no more misfires. Swapped old one back and misfires happened. So misfire issue was the power pack. The coils looks a little crispy in areas so those are being replaced. However the voltage is still running too high, 16.5 when driving at open throttle. I think it’s a combination of the bad power pack and a bad rectifier. I have a rectifier on the way also. Hopefully that solves the voltage spikes.

 

[Rom6100]

And another update. Swapped out the power pack and no more misfires. Swapped old one back and misfires happened. So misfire issue was the power pack. The coils looks a little crispy in areas so those are being replaced. However the voltage is still running too high, 16.5 when driving at open throttle. I think it’s a combination of the bad power pack and a bad rectifier. I have a rectifier on the way also. Hopefully that solves the voltage spikes.