1999 Johnson 90hp lost partial power after trimming too high

[Rom6100]

Hey all, new motor and boat to me, took it out first day, ran great, last run of the day I trimmed a bit too high, heard the prop lose grip and immediately trimmed down. After that it felt like I lost a cylinder. Boat was running 37 at wot and then would only get to 25 at wot and much slower acceleration. Not sure if something occurred in that quick amount of time. Motor is a 99 Johnson 2 stroke 4cyl. It has the optical ignition system. I’m hoping it’s something simple like a coil, but it doesn’t make a ton of sense to me that a coil would go from that. I haven’t checked compression yet. It fires up fine and no problems starting, idle seems fine. Pumped water fine. I’m going to try it again tomorrow on a local lake and hope it was just a fluke but I’ve had a really bad run of luck this year with 90hp 2 stroke motors and I’m really hoping this isn’t going to be the 3rd problem. Anyone ever have something like this happen before when they trimmed a tad too high?

 

[boobie]

Do a compression check on it and then a spark check.

 

[Rom6100]

120 across the board for compression, any suggestions on how to check spark?

 

[393Clevor]

Ya know I always see compression readings that state 120 across the board.. and for me I have done these tests on just about every type of engine and it always has some difference in compression be it might only be a few pounds but different none the less.... So my point here is I never hear anyone reminding people to clear the gauge between tests.. ya know that little pressure relief valve on the side of the gauge.. You could be checking a bad 90lbs hole and the gauge it still on 120 from the last test done...

 

[Rom6100]

I zeroed the gauge each time, it might have been a few pounds difference but it was a shitty rental gauge set from an auto store and it would lose a couple pounds by the time I got back to it. Was hard to get and exact number by myself. But there wasn’t any that topped out at 90. So that was a good sign. The gauge was difficult to set up so I can see it each time as the engine kicked and everything moves.

 

[Chris1956]

Put a timing light on each spark plug wire and crank her over.

 

[Rom6100]

If I was to start it up and drive it on the water, if it still acted poorly l, can I pull each spark plug one by one to see if there is a change or no change? Like pull top right, drive it, put it back, etc. if I get to one that it drives like all of them connected with the wire disconnected can I assume that is not getting spark?

 

[boobie]

Yes, you're doing what is called a cyl drop test. Good show. When you find one that makes no difference that's the cylinder that has the problem or maybe cylinders.

 

[Rom6100]

I changed plugs and went for a ride, ride fine the first run, sat for a bit then tried again and same thing loss of power, I removed each plug one by one and narrowed it down to one plug not firing, Can I assume this is a coil problem?

 

[iggyw1]

I changed plugs and went for a ride, ride fine the first run, sat for a bit then tried again and same thing loss of power, I removed each plug one by one and narrowed it down to one plug not firing, Can I assume this is a coil problem?

One more test I would do if it were my motor before I drop any $$ into the motor. Trade the spark plug wire with a known good wire on the cyl. that is dead, and see if it is not just the spark plug wire.

 

[Rom6100]

That is a good idea, I already ordered the coil, if it’s not that pretty sure I can return it from amazon, I’m not sure if this is related but the Tach in the boat is not accurate either and jumps all over, does not match the engine speed. Any guess on if that’s related or separate issue? Could a faulty rectifier cause this?

 

[iggyw1]

That is a good idea, I already ordered the coil, if it’s not that pretty sure I can return it from amazon, I’m not sure if this is related but the Tach in the boat is not accurate either and jumps all over, does not match the engine speed. Any guess on if that’s related or separate issue? Could a faulty rectifier cause this?

I can not tell you if it is related or not or if a faulty rectifier could cause this. I am not one of the gurus on here that know a lot about motors, however, I had a tach that went all over the place even at an steady throttle. I got under the dashboard, removed the wires from the tach one at a time, and cleaned up all connections & wires. That solved my tach problem.

 

[oldboat1]

All kind of indicates the rig hasn't had a lot of recent hands-on care. I would change out the impeller before anymore running. A blown rectifier can affect the tach -- is the battery charging? Speaking of batteries, was the battery polarity reversed at some point? (will destroy the rectifier). Get an oem manual for your motor, if you haven't already done so.

edit. maybe this: https://www.ebay.com/itm/1999-Evinr...385789?hash=item56bfd1cf3d:g:k9QAAOSwfVpYrfIU

 

[Rom6100]

No idea if the battery poles were ever switched, it’s a new to me boat. Batteries seem to charge as indication of volts in the 13’s on the fish finder, and yes I can agree this motor hasn’t had much hands on care. It sat for about a year the owner had said. Hoping it’s going to be an easy fix. I appreciate the manual also. I believe that one is correct.

 

[boobie]

What did you find out about the one plug not firing ??

 

[Rom6100]

Double post

 

[Rom6100]

Nothing yet, I need to go back to the lake with some tools and try switching out wires and coils. I didn’t have any tools with me yesterday. Still seeing if anyone has any insight to causes of plugs not firing.

 

[Chris1956]

Sure, spark plugs do not fire, if they do not get spark, or fuel or air, or have the wrong timing. Outboards can also get water in the cylinders. Not all causes are equally likely.

You must determine if the spark plug is getting spark and not firing the cylinder, or it is not getting spark.

If no spark, I would check the wiring to the coil. Look for corrosion.

You can switch the wires on the coil from a running cylinder and see if the no spark problem stays or moves with the wire switch. That tells you if it is a power pack issue or coil issue.

If getting spark and not firing, check the spark plug wire for arcing to ground. If the coil generates a spark, and the spark plug is not firing, the spark went somewhere. Usually you can hear the spark arc.

Next, pull the brass screw/plug at the base of the carb of the bad cylinder and see if fuel comes out. Inspect the carb linkage.

If she has spark, fuel and air, the carb could be clogged. Does it leak?


For the tachometer problem, your motor likely has a voltage regulator, versus a rectifier. I would look for corroded wiring leading to the tachometer, since it is acting up. I would run the motor and add some load (running lights etc) and check voltage before and after adding the load to see if she charges.

 

[He rik]

Nothing yet, I need to go back to the lake with some tools and try switching out wires and coils. I didn’t have any tools with me yesterday. Still seeing if anyone has any insight to causes of plugs not firing.

Basicly plug bad, plug-lead/coil bad or no or too much fuel if u got comp.,

Was the plug wet or dry?

Runs cold and not warm could be coil, change the coil with anoter cyl and see if the problem move, if it does change plug-leads and see if it moves again, if it does u found the problem, if not maybe the coil.

If problem dont move after changed coils, change the plug.

The erratic tach you got could be bad wires or connections on the gauge or just a bad tach, check all connections, especilly the ground.
I belive your tach-signal comes from the ecu if I understand correctly what engine you got so I dont know if the rect/reg have something to do with it.

 

[Rom6100]

I appreciate the input, I’m going to try and get Out on the water later today and test some of the things mentioned. I will report back. Thanks again