1986 Johnson GT150 tach not working and sometimes only running on 3 cylinders

I have a 1986 Johnson GT150 J150STLCDC that has been giving me troubles since last summer. My brother was using it and hit a wave very hard and stopped the boat dead. The boat shut off when he hit the wave. Afterwards it started right back up and ran fine. He stopped shortly after and shut the engine down. Everything was running fine up to this point. This is where it all went downhill. When he hit the starter it just made an odd whirring sound like the bendix gear wasn't engaging, so he went back to take the cover off the engine. When he got the cover off he saw that the nut, washer, and spring had all flown off the starter. Next smoke started rolling out from under the flywheel on the back side of the engine. In the area of the regulator/rectifier from what i can gather from his description. He had left the key in the on position, he turned the key off and dumped water on top of the engine to stop the smoke. :facepalm: After that the engine started up using a rope, and he drove it back to shore and loaded it back onto the trailer. But now found the trim wouldn't work.

When he brought the boat back to me there were many loose screws all around the boat, that's how hard he hit this wave. The trim was not working because of a blown fuse, but whenever I replaced it the fuse would blow as soon as I plugged in the big red wiring connecter. With the connector unplugged the fuse would not blow and the trim worked fine. I completely disconnected the stator, and regulator/rectifier from everything but the fuse just kept blowing. I worked on it for countless hours at the end of the season last year before I finally gave up for the winter and went snowmobiling.

When I got back to work on it this spring somehow the fuse has stopped blowing and the trim works fine. I reassembled everything and it started right up and the trim works great. However when it is cold it sometimes seems to only run on the right 3 cylinders until the engine warms up and then it has full power again, although while running it sometimes hesitates and momentairily goes back to 3 cylinders, but comes out of it before the boat even comes down off plane and takes off again. I have had it out 5 times hoping that the not running on all cylinders problem was from stale gas and now I've run a full tank of supreme through both tanks so I don't think it's a fuel issue. I got it out today to try testing if the port side cylinders are getting fire but it has been running perfectly all day. Go figure. Aside from the not running on all cylinders all the time the tach is not working.

With the engine running at idle I read 12.9V across the battery, I connected the grey wire that runs to the tach to the yellow/grey wire and the tach works properly, I measured the resistance between the brown and brown/yellow wires and i get around 1035 ohm on each side, when measuring resistance between the white and blue/purple/green wires i get around 13 ohm for all 3 readings on both sides. I am trying to narrow down if this could be a bad stator, regulator/rectifier, or both.

Any help on this issue would be greatly appreciated.

Thanks in advance, Scott

Re: 1986 Johnson GT150 tach not working and sometimes only running on 3 cylinders

do em both they probably melted down in the aformentioned fray .... you may have gotten a power pack too so check the voltage out put to the coils you should have about 250v going into the coil from the pack

Re: 1986 Johnson GT150 tach not working and sometimes only running on 3 cylinders

Which wires do I want to test to see the voltage output to the coils? Is that the voltage between the brown and brown/yellow wires?

Re: 1986 Johnson GT150 tach not working and sometimes only running on 3 cylinders

There are two pairs of leads from the stator to run the ignition system. One pair to each power pack. One pair has a tan and a tan with yellow tracer. The other pair has a tan with black tracer and a tan with white tracer. Disconnect the two connectors. Inside you will see the terminals marked A and B. When you crank the engine you should get at least 150 volts between each A/B lead. You will need a peak-reading voltmeter to correctly measure this voltage. The near fire was probably the water cooled combination rectifier/regulator. I'd check it for output. Likely it is damaged, since your tach gets it's signal from that rectfier/regulator and you indicate the tach is not working. You should follow the factory service manual for instructions for putting a 40 amp ammeter in the stator charging circuit and then run the engine at 4500 rpm to check it's output. You have a high capacity 35 amp alternator on that engine (vented flywheel) so you are running a lot of current through it. If it is damaged internally, it can start another fire.

Re: 1986 Johnson GT150 tach not working and sometimes only running on 3 cylinders

Ok. Thanks, I'll try replacing both the regulator/rectifier and stator since I have spares of both from a parts motor that came with the boat. I'll post again how I make out.

Re: 1986 Johnson GT150 tach not working and sometimes only running on 3 cylinders

So I finally got everything working properly today. I replaced the stator, and regulator/rectifier first and started it up. The tach started working fine but the engine was only running on the right 3 cylinders still. I figured that not all 3 left hand plugs or coils would be gone at once so I replaced the left power pack. That fixed it. Now it is firing on all 6 cylinders and my tach works. Luckily these were all spare parts since the boat came with 2 parts motors. Now i just need to loosen up my super stiff steering cables and it'll be all good to go.

Re: 1986 Johnson GT150 tach not working and sometimes only running on 3 cylinders

Most steering cables are not meant to be lubricated. There is no location to apply lube. They will deteriorate with age. The inner cable can fray at the bends over time, and drag excessively on the outer casing. If they are stiff, you may need to replace them.

Re: 1986 Johnson GT150 tach not working and sometimes only running on 3 cylinders

That what i'm seeing from reading here, although I've found a couple posts about people making a cable luber and i think that may work. My cables look like someone put a grey paste in them and it's so thick it's making them not want to move. I'm going to give that a shot first and see how I make out. Much cheaper than replacing 2 cables.

Re: 1986 Johnson GT150 tach not working and sometimes only running on 3 cylinders

If the inner cable is fraying and is rubbing against the outer sheathing, lubbing the cable won't help much. Guess it's worth a try.
Since you have a dual cable system, I'd be inclined to pull one of the cables off the helm and see if the other is stiff. Then switch-replacing the first and take the other on off and check it. You may find only one cable is the problem.