Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YES)

[blackwaterstout]

I'd love to hear your thought on what might be wrong.<br /><br />I took the boat out today for it's semi-maiden voyage. The '79 motor has good spark, good compression (135psi), starts easy, does not stall, has new plugs, new clean gas, etc. But for some reason it only runs at about 30% at full throttle. I could only get it to go 6 mph. At first I thought maybe my throttle cable was not opening my carb all of the way, but I think it is. The weird thing is that after travelling up the river about 1/4 of a mile the motor started to rev up nicely and appeared to be at full 100% performance. but after about 5 seconds it sags back down to the original 6mph. We put about 40 minutes on the engine today and spent a lot of time trying to figure out why the engine surged up to peak performance. We could not figure it out. It surged like that twice in those 40 minutes. <br /><br />So in summery I'm not sure what is causing my poor performance. Like I said, the plugs are new, the gas is good, the engine idles great and is easy to start. Just not sure why it's acting like it is. I'd think that if the carb wasn't opening fully then I would've never gotten the surge. The only thing I can think of is that the carb might need cleaned or something. What do you guys think?

 

[BoatBuoy]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Carb needs cleaning. I suspect your problem was caused by a small amt. of water in the float bowl. Quick cure - remove the bowl drain screw, tilt the motor forward to empty bowl. Correct cure - remove carb, disassemble, soak, install carb kit. Check tank and lines for water.

 

[racefan2]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

check the gas tank also as my 9.9 Johnson did the same thing and the gas tank was bad as it was not holding pressure and it was not the cap.

 

[BoatBuoy]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Also, make sure you're not sucking air anywhere along the fuel path.

 

[Walker]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Check spark while you are under load.

 

[blackwaterstout]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Whats the easiest way to check for air leaks in my fuel lines? My gas tank is the stock 6 gallon metal tank that came with those engines. It has a vent on top of the gas cap that I open when I run the engine. I should keep this open while running right? When I primed my bulb it took about 4 or 5 squeezes to tighten up and after I started the engine the bulb was a little softer. But as far as I know thats normal.

 

[BoatBuoy]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

All that sounds right, provided you're not observing any fuel leaks after pumping bulb.

 

[blackwaterstout]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Once I pump the bulb up and get it nice and tight, will it stay tight and for how long? (Not running the engine). Also, if it's tight and I apply slight pressure to it will I be able to hear or feel more gas creeping from the bulb?

 

[Goodoleboy]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

You should not feel or hear gas going through line after it is pumped up firm.<br /><br />You can check for air leaks by smearing grease on all gas line connections, if motor then runs correctly then you know you have an air leak.<br /><br />Then start wipeing clean one connection at a time untill engine falls back to low rpm,s. When that happens repair that connection.<br /><br />You could also have a sticky needle and seat. Float could be rubing on side of bowl.<br /><br />You can use an inductive type timeing light on each plug wire while motor is boging down to see if your geting fire during this time.<br /><br />Good Luck!

 

[fireman57]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Sounds like a spark problem as Walker suggested and Goodoleboy backed up. Probably a coil breaking down under a load. Spark test would be the first thing I would do.

 

[blackwaterstout]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

How do you do a spark test under load? I've done a standard spark test and both plugs seemed to be fine.

 

[blackwaterstout]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Well I spent a lot of time today looking at things and doing some tests. I examined the carb and it looked great. I'm wondering if the previous owner had recently replaced it because it looks new. I didn't disassemble it. Instead I decided to pull the new spark plugs I had put in a few weeks ago. They have a total of about 40 minutes on them. What I found is that the bottom cylnder's plug looked new while the top cylnder's plug looked slightly used as I had expect it to look. That told me to recheck the spark. As you've problaby guessed (and as others mentioned during my troubleshooting) there was no spark on the bottom cylinder. I had originally checked the spark when I bought the boat a while back and could've swore it worked back them. Maybe I'm loosing my mind. I rechecked the compression too which yielded readings of 135 and 130.<br /><br />So the bottom line now is something is causing me to not have a spark on one cylinder. Could it be a bad coil? Bad power pack? If the power pack was bad would I still be getting good spark on the top cylinder?<br /><br />What is the best way for me to diagnose a faulty coil? I do not want to go buying parts until I'm sure what is wrong. I went through several electrical tests in my Seloc manual and after borrowing a better ohm meter from my neighbor was able to gets some results that seemed to be inline. There were a few tests I could not do because they required a "neon light meter"..... Whatever the heck that is....<br /><br />I can buy a coil for $25 or a power pack for about $60. But I'd rather be a little more certain of what I really need.<br /><br />Once last question, would it be OK to run this boat in water at slow speed in order to get a 1/2 mile up the river for some fishing. I had a small fishing trip planned for tomorrow and in case I can't get it fixed I'd like to take the boat. Will this hurt the motor or have adverse affects down the road?<br /><br />Thanks for the help guys.

 

[Goodoleboy]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Put the coil thats got spark in place of the one that dosent. If no spark follows same coil then replace.<br /><br />Good luck!

 

[blackwaterstout]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Can I do this by just swapping orange wires?

 

[OBJ]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Nope....changes the timing of when the pistons on on top. Now if you can change the orange wires and spark plug leads also, that would work, but I don't know if the spark plug leads will be long enough.

 

[Walker]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Yes, you can do it just to check spark. Pull the spark plugs and use a spark tester to check with a 7/16" gap

 

[OBJ]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Yes, what Walker said....but don't try to run it like this.....that's what I was getting at.... Thanks for clarifing Walker...

 

[blackwaterstout]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

OK. So if I swap the coils and the problem now moves to the top cylinder then I can be pretty sure that replacing the coil will cure my problem? What if the bottom cylinder stays sparkless? Does this pretty much mean it's the power pack?<br /><br />Also, would it hurt to run the boat a 1/2 mile up the river and anchor with only one cylinder? I assume it won't but I want to check first. I don't plan to run it hard, just want to get to a prime fishing location.

 

[Goodoleboy]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Go for it....Lots more fun fishing than workin on ah stupid motor any day.<br /><br /> And yes to all on your coil and power pack question.<br /><br />Good Luck!

 

[blackwaterstout]

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

Re: Johnson 25 throttle issue has me stumped (UPDATE 2....COIL-NO, POWER PACK-YE

UPDATE NO. 2.<br /><br />I swapped coils today and found that the bottom cylinder is still not firing. So I can rule out the coils as the culprit. I'm pretty confident that the power pack is bad. Thats the only thing I can think of. What causes power packs to go bad?<br /><br />I looked the pack up online and found the sierra pack sells for $50 while the Barbardier pack sells for $65. Do you think it's worth paying the extra $15 for the OMC pack? None of the local shops have it in stock and I will probably have to order it online. I had bad luck with a Sierra water pump this week and I am a little apprehensive about their products now. But I'm on an extremely tight budget and am considering it. What are your thoughts.