Johnson 115 lost power

rjbaiad

Cadet
Joined
Mar 14, 2003
Messages
8
Not sure what really happened. I had recently bought this boat from a friend. First time I put it in the water the motor froze up due to the oil injector going out (stupid warning system didn't work right either). I had the motor rebuilt and took it out. I had no problems running it the first time, except that after of being on the water for about 2 or 3 hours the idle started fluctuating rapidly to the point to where I had to kill the engine to keep the motor from racing. The next time we took it out we went tubing for a couple of hours and all off a sudden the motor lost power, but the motor quit racing. It woulnd't even plane out. So I got home and someone told me to change the spark plugs so I tried that. Took it out the next time and the motor ran better, but it was very sluggish to take off and I noticed a growl in the motor when it was at WOT and in the process of planing out. It also will top out at 5500 RPM where it used to top out at 6000 RPM with the motor trimmed. I put the motor in the shop and the man told me that I had one cylinder at 131 and the other three were 119. He said he found a disconnected fuel line to one of the cylinders. We took it out and it made no difference, but he swore up and down I was not trimming the motor right, which I believe he was wrong since it used to take off and run faster than it is now. I took it to the river the other day and ran it about 45 miles and when I came home I took one of the spark plugs off on the lower left cylinder and it was badly fouled. I had never seen a plug fouled so badly. It had oil caked onto it. Can anyone tell me what the heck is going on? I really don't know alot about motors so I need some pointers! I'm going to try and check compression tomorrow so hopefully that will tell me something.<br /><br />I had a previous post but didn't tell the entire story, so this tells all. <br /><br />Ryan
 

bonitoman

Petty Officer 1st Class
Joined
Jul 9, 2002
Messages
292
Re: Johnson 115 lost power

Try running the engine on a hose for a few minutes.Then check compression. Get some plastic pliers with the engine running pull the spark plug wire and see if the rpms drop and the keep the boot a 1/2 from the plug. You should see that spark jump from the spark plug wire to the plug. It sounds like the plug that is caked with oil is not firing and that could be the coil. You only have a few choices. Bad plug,wire, power pack , coil which is what it probably is and when you get under the flywheel you have the stator and trigger. First verify you have good compression then test your ignintion. Good luck
 

rjbaiad

Cadet
Joined
Mar 14, 2003
Messages
8
Re: Johnson 115 lost power

Thanks for your reply. I do have one question however. If it was not the plug firing woulnd't it be misfiring somewhat? I don't have a lot of experience with motors so I really wouldn't know, this is just what someone told me. Haven't had a chance to check the compression yet. I went to go pick up a gauge and the place didn't have one.
 

OBJ

Supreme Mariner
Joined
Dec 27, 2002
Messages
10,161
Re: Johnson 115 lost power

rj....were the carbs rebuilt when the engine was overhauled?<br /><br />Agree with bonito...get a warm compression test. Also, you may want to check the lower carb for flow back indicating a bad reed for the cylinder in question. The fouling may be due to too much fuel getting to the cylinder.
 

rjbaiad

Cadet
Joined
Mar 14, 2003
Messages
8
Re: Johnson 115 lost power

To be honest I'm not sure if the carbs were rebuilt or not. Here is the deal though. I did a compression test today and they were pretty much all the same. 2 cyls had 100 and one had 103 and the other had 101. I didn't do a warm compression test though. I did it on a cold start. I was thinking about pulling the carbs off myself and checking the reeds to see if something was wrong. I read the first post so fast that I really didn't pay attention to the "warm" part of doing the compression test. Is this going to make a big difference?<br /><br />Ryan
 
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