15hp '82 johnson loses power/dies at high throttle on the water

[RedbaranTX]

Re: 15hp '82 johnson loses power/dies at high throttle on the water

Appreciate it. I get the feeling it's fuel too. However, the bulb stays pretty full when throttled up. I can feel it pulling fuel but it doesn't get compressed, it keeps up with the demand. When I took it out the last time I tried pumping the primer bulb both vigorously and steadily, and it made no noticable difference to the issue. The pump does pump, I've disconnected the line as you described.

I may re-re-build the fuel pump just to count it out for good,it's a cheaper fix than most anyway. I'm wonderin though, is there something that could be causing the pump to push too much fuel into the carb and be floodig it? I'm playing off my instincts here, I tried to really focus on what the motor was doing when it fluctuated and it felt similar to an engine being choked out or flooded.

Far as piston rings go, when I had the head off I looked in close and the ring I could see seemed just fine. There was also just a little play in the piston all the way around, so I would think this would discount a stuck ring.

 

[Will Bark]

Re: 15hp '82 johnson loses power/dies at high throttle on the water

My 15hp 1977 Evinrude was doing the exact same thing as yours, run all day at 3/4 throttle and then die out at WOT. Would start right back up and good to go at 3/4 but not higher. Solved my problem by moving float drop to the full 1&1/2 inches maybe you can try that if you haven't done so already. Good luck.

 

[dazk14]

Re: 15hp '82 johnson loses power/dies at high throttle on the water

Have you had this motor properly in the past?

A video with sound could be helpful.

 

[Rick.]

Re: 15hp '82 johnson loses power/dies at high throttle on the water

Well both numbers improved and that's a good thing. It could be your high speed circuit in the carb. is not clean enough. It could also be spark on one cylinder is poor once engine has warmed up. These things can be frustrating but your getting to know more and more and it will be easier to diagnose next time. Your compression is still weak IMO but it might come up with regular use. With engine off, you should be able to pump your bulb until it gets very hard. No flow through the carb. at that point. Your description sounds like there is flow. If that is true your float/needle is not shutting off gas flow completely as it should. Rick.

 

[RedbaranTX]

Re: 15hp '82 johnson loses power/dies at high throttle on the water

Will Bark: That sounds like a logical cause/solution, thank you. Can anyone tell me the proper way to adjust the float on this Carb? I've been told to just bend the metal piece that the float is attached to but it doesn't seem right...

Dazk14: I've had the motor for a short time and hadn't run it on open water until this season. It always ran great on muffs and in a bucket so I made to rookie assumption that it was good to go. I'll try to get a video but for now the audio goes like this: "Go, Go, GoGoGo, Yaaaaaaaaaaaaaaaaaaaaaayyyyyyyy!!!! Awwwweee, crap.

Rick: I will clean/inspect the carb tomorrow, I'm just gonna start from the top again cause I think I missed something simple somewhere along the way. I may have explained myself poorly about the primer bulb, I was describing pumping it while the engine was running. It does get solid when the engine is off. I also ran a buddy's motor on my tank and line today and it had no problems, so that's one thing that's working for sure.

Bad news now, after changing the head gasket I hear a knock, or tap, from one of the pistons. Could this be a result of the gasket not aligning properly? I noticed there was a little play in it while reinstalling but it was difficult to do much about it. If not, what else? This was not happening before.

Thanks to everyone as always. If I keep this up some day I may be able to ANSWER a Post!

 

[Will Bark]

Re: 15hp '82 johnson loses power/dies at high throttle on the water

The way I do it is to have the bowl off and the carb upright with the float hanging down; measure the top front edge of the float to the bottom flange of the carb and adjust the distance to 1 &1/2 in. bending the little metal tab behind the hinge pin carefully; dosen't take much. makr sure that the needle falls down when the float drops down. Hope it works for you. Someone else will have to help you with the noise problem.

 

[outlaw241]

Re: 15hp '82 johnson loses power/dies at high throttle on the water

i had same problem with a 25hp were it would die at wot, come to find out the previous owner had the wrong upper water tube grommet in it and at wot it was not sealing the hole,it always pissed water out the tale tale, but i think the volume of water was not there at wot an it would die ,but would start right back up,just check to make sure the upper grommet is in good shape ,mine also has a plastic washer that slides on the water tube under the grommet i think to help hold the grommet in place an not allow it to slide down the water tube. hope this is of some help.

 

[Rick.]

Re: 15hp '82 johnson loses power/dies at high throttle on the water

It's never a "oh, I see the problem" is it? I can not imagine why it would suddenly start to knock. I would pull the head once more and have a look at things. You can probably re-use the gasket as it is so new. I really can't say for certain but I don't think you can install the gasket wrong as the design engineers made it so the gasket can only go on one way. Perhaps your using a wrong plug that is reaching the piston top? I'm more inclined to think it is a mechanical noise coming from somewhere else but I may be trying to be optimistic here. Did you have the flywheel off at the same time as the head? Perhaps the flywheel is tapping on your coil or some such thing. I am grasping I know.
If you determine the knock is internal then you"ll have to break the engine apart. BKtheKing would be able to help you more than I as he has been into the innards and has a much better knowledge base than I. (he is the king!!) He will get you going or at least give it a good try. Rick.

 

[the machinist]

Re: 15hp '82 johnson loses power/dies at high throttle on the water

If you will go back to the "Frequently Asked Questions" at the start of this OMC page, down on the bottom of page 1, you will find a link to my "9.9/15hp OMC Engines by "The Machinist" ". Here I have many articles on repair for these motors. One being on carburation.

Good Luck

 

[RedbaranTX]

Re: 15hp '82 johnson loses power/dies at high throttle on the water

Will Bark Is the MAN!!!!


I went and adjusted the Float in the Carb as high as it could go and BAM! It's running full out no problem! The knock is still there, I re-installed the head gasket and didn't see anything amiss. I'll just let that one be for now, I need to actually use the motor or I may as well not have it at all.

Thanks to everyone for your help, and hopefully someone else will be able to learn from this thread. I'm going to quit posting on it though, it's long enough as it is. I'm sure I'll be back with a different question before too long.

Thanks again!

 

[bktheking]

Re: 15hp '82 johnson loses power/dies at high throttle on the water

I still don't like the compression numbers, decarb again and see if it comes up.
Glad the float fixed it, now you know.

 

[jeffersondodson561]

Re: 15hp '82 johnson loses power/dies at high throttle on the water

Whats the condition of your portable fuel tank? Vented properly? Fuel restiction?

 

[Will Bark]

Re: 15hp '82 johnson loses power/dies at high throttle on the water

Great! Glad to see it worked for you ; enjoy!