1998 25 hp Johnson 3 cyl over heating

[Nicksr]

Hi Every one!
I have been reading these threads and learning allot about my out board. Thanks again
Here is my issue...
I have over heating problem (I think)... I replaced the thermostat and the water pump. Cleaned the carbs as well and I removed the self oiler. now mix the fuel 50:1. The engine runs perfect as long as i keep it full throttle but as soon as i troll for a bit the engine seems to get over heated and bogs down and will eventually will stall. It will start right back up but still bogs out. If I let it cool for a half hour it runs fine again for a bit. Could it be the timing? I have good pressure from the pee hole at idle speed.
Your help is appreciated!!!!
Nick

 

[Daviet]

Re: 1998 25 hp Johnson 3 cyl over heating

Have you checked the spark when it stalls, sometimes an ign component will overheat and cause problems. When the component cools off it will run properly.

 

[Nicksr]

Re: 1998 25 hp Johnson 3 cyl over heating

Check for spark? what ign part could over heat?

 

[nwcove]

Re: 1998 25 hp Johnson 3 cyl over heating

"Check for spark? what ign part could over heat?"

pretty much all of them. i had a 2000 (maybe 1999) 25 hp triple, and the powerpack failed 15 mins into its break in procedure. didnt act like yours tho, it just lost spark to one cyl, and i limped back to the dock.

 

[Nicksr]

Re: 1998 25 hp Johnson 3 cyl over heating

Update!!
Well... I replace the power pack with a new one from the dealer and looks like the problem is solved. Just wondering How hot should the engine get when it runs? i can touch the area around the thermostat for a split second before its to hot to touch.
Also I just developed a new issue, the kill switch now does not work. Is this related to the new Power pack ??
Help needed again please!!!!
Nick

 

[hidef]

Re: 1998 25 hp Johnson 3 cyl over heating

Check to make sure that the round plug located at the bottom left of the power pack is tight and both power pack ground wires are connected and tight. The temp will be highest around the spark plugs and thermostat housing where the thermostat screws in. You need infrared thermometer to accurately check the temp. It should be around 145 degrees or so on the head if I remember correctly. If your water pump is pumping and you have a steady stream at idle you should be okay. Your engine does have a temp sensor and the engine will go into SLOW mode if it overheats limiting engine RPM to 2500.

 

[Nicksr]

Re: 1998 25 hp Johnson 3 cyl over heating

Ok I double checked and cleaned all the connections and ground, still no kill switch. I took a ohm tester to the switch and nothing. could it be the switch all of a sudden? or the power pack is faulty?

 

[hidef]

Re: 1998 25 hp Johnson 3 cyl over heating

You can bypass the switch and ground the black and yellow wire running into the power pack. If the engine dies the power pack is fine if it stays running the kill switch is bad.

 

[Nicksr]

Re: 1998 25 hp Johnson 3 cyl over heating

How do I ground out black and yellow wires?
I took out the boat today for a test run. It ran perfect for a while... I had it at full throttle for about a mile then I trolled around and fished for 45min. or more and so far it was perfect. I decided to head back and went full out again but after a few min. the motor started to buck or cough and so i went half throttle and it was ok for a bit but then it started to act up, and then i went slower and it stalled. It would not start right away but after a few min. it started up, ran for a bit the acted up again then stalled, got to a point were i could only go trolling speed for a bit then stalled again.
frustrated now. I was felling pretty good there for a bit , thought I had it figured out!
Any ideas??
Thanks again.

 

[Daviet]

Re: 1998 25 hp Johnson 3 cyl over heating

You are going to have to troubleshoot the system when it is acting up. Use a timing light and check each plug wire and see if you have constant flashes. If you do then try squirting some fuel mixture into each carb and see if it picks up. At least you will find out if you are having a fuel or ignition problem.

 

[hidef]

Re: 1998 25 hp Johnson 3 cyl over heating

Use a probe that you can ground to the block and with the engine running and the plug disconnected touch the probe to the pin for black and yellow wire. This will cause the engine to stop if it doesn't you have a bad power pack. You can also test kill switch with a ohm meter connect one end to ground and the other end to the black and yellow wire on the wiring harness. The ohm meter should read open. Push the kill switch and the meter should read zero if it doesn't you have a bad switch.

Your power pack has a warranty if it is faulty the dealer should replace it.

 

[Nicksr]

Re: 1998 25 hp Johnson 3 cyl over heating

Ok I did ground out the black and yellow wire and the motor turned off!! I did this a few times to be sure. No reading on the ohm meter so it must be the kill switch.

I only ran the motor for a few minutes and when i gave it some throttle it acted up and shut off, (so i assume there is not a over heating problem) it would not start up right away but after a minute it did. I right away gave it more throttle and it stalled again so quickly I took out one spark plug (i do not have a timing light)and checked for spark and there was none. Waited a minute again and I had spark and the motor started with one plug out. Put the plug back in and I repeated this again when the motor stalled and again no spark. Sure enough a minute later there was spark again.

Thanks in advance!!!!