1994 Johnson 70 no power under load

[avisalem155]

Hi All,

I recently acquired a 16' bowrider with a 1994 Johnson 70 ELERC (3 cylinder 2 stroke). I have rebuilt the carbs already and replaced some fuel lines and primer bulb setup. The problem I am having is that under load, the boat won't break 3,000 rpms. I pulled the coils, boots, and spark plugs, and it seems as if the middle cylinder isn't firing. I assume this because when I pulled the boot off the plug, the rpms didn't drop at all. Switched around coils and everything and still no change when pulling the boot for the middle carb. I actually pulled the boot off by hand for all 3 plugs (yep nice shock), but the middle carbs shock didn't seem to zap me as bad. Could it be the powerpack? I just got a spark tester and compression tester and will perform those tests tomorrow. How should I go about testing the ignition system?


Thanks,
Avi

 

[mfkadz]

Seeing s you just rebuilt the carbs... You can squirt some carb cleaner or ether into the offending cylinders carb and see if that does anything. If that cylinder kicks in you still have a fuel issue.

You can also try swapping the plug out of the offending cylinder with another and see if the issue moves.

Here's a link that should help you with the ignition....

http://www.cdielectronics.com/wp-con...20-%202012.pdf

mike

 

[avisalem155]

Thanks Mike. I swapped the plugs and boots and the issue still remained on the middle cylinder. If I keep pumping the primer bulb I get a nice amount of gas coming out from the carb throat, maybe I can try squirting some premix into the cylinder directly? Any easy way to see whether the cylinder is definitely firing or not?

Thanks,
Avi

 

[WernerF]

First thing to do is a compression test..

 

[mfkadz]

ok, I think you just said what your problem is.

The bulb is used to prime the carbs is all. As in fill the bowls before starting. You should not get fuel into the carb throat when pumping the bulb. I am guessing you are flooding that cylinder. So no fire there. My guess in you do not get fuel into the throat on the other two? Or much less.

As before, you just rebuilt the carbs. Take that center one off and recheck the float. It should be level when the attached needle seats and stops the gas from coming into the bowl. It's soft metal and bends easily.

I did the same thing on a carb. Did it on the first and forgot on the second.

mike...

 

[avisalem155]

Actually I get the excess fuel on all 3. I thought it was strange that squeezing the bulb would start squirting gas from the throat of the carb by the butterfly, so I actually took the middle carb out and checked the float level and all was good. I saw that there is 2 lines, one going to the carb body to fill up the bowl, the other goes in to the top of the carb, through the diaphragm, and into the throat of the carbs, for starting purposes. Also, since i am only priming at startup, there would be no reason for the middle carb to stay flooded. When i pulled it out, the float seemed to be doing exactly what it was supposed to do. Since the other 2 carbs behave the same way anyways, I am leaning towards an ignition problem rather than fuel.

Thanks,
Avi

 

[mfkadz]

That's good. Much easier to troubleshoot in front of the thing. ;-).

One other thing if you have not done it is to swap coils with another cylinder.

If the swap has been done or does not change anything you have the link to the CDI troubleshooting pages. Good stuff there.

mike

 

[avisalem155]

Yes I definitely agree. Swapped the coils too, problem still on the middle cylinder, but like I said, every time I grabbed the boot from the middle cylinder, the shock was a lot less intense than the other two cylinders, but there was definitely some power there....I will definitely try the CDI pages, I had actually printed them out earlier this morning suspecting I have a power pack issue. I am not to knowledgeable about the stator, rectifier, and triggers, and my electrical knowledge isn't great either. Do you think it can be anything else besides the power pack?

Thanks,
Avi

 

[avisalem155]

No Title

Ok so I tested compression, doesn't make sense but here we go. The top cylinder is 50, the middle is 25, and the bottom is 50. These are all extremely low, I'm not even sure how the engine ran at all! I pulled the head and the top cylinder wall has some scoring, the middle cylinder wall has some really bad scoring, I can easily feel it with my fingers. I am posting some pics for you to see. I don't think I'd be able to rebuild this engine, any advice is welcome. Thanks

 

[mfkadz]

ouch.... yuk....

If the head is sleeved it might be re-sleeved. The one cyl might be to deep even for oversized rings if you have them honed.

mike

 

[avisalem155]

Is honing something I can do myself? Might be worth a shot

Thanks
avi

 

[mfkadz]

Honing is more for light scratches. I think your beyond the home repair of those cylinder sleeves

mike

 

[avisalem155]

I couldn't believe that the compression came back at 50 and the engine was running, so I went back to the store and swapped out the compression tester I had. As luck would have it , the tester wasn't correct. Just tested the compression again with the new tester. The top cylinder was 95, the middle was 75, and the bottom was 100. Being that 75 is low, I sprayed some two stroke into the cylinder and retested, the middle cylinder went up to 95, then slowly started decreasing every time I tested after.

I understand that regardless my cylinders have some scoring, would it be possible to get away with maybe replacing the head gasket and possibly ring job? I don't have much money in this boat, and I don't want to put a lot into it either, so if I can get a couple seasons out of it I'd be happy....

Advice is appreciated

Thanks

 

[schematic]

if you keep running it, it may cough out a ring and damage the head adding to the cost of repair. Do it now before all hell breaks loose....Looks like a easy rebore

 

[emdsapmgr]

That middle cyl needs work. Piston needs to be replaced. If you can hone the scratches out, you can maybe get by with just a new std, piston. If the scratches won't come out, you need to bore it till they do. Factory pistons for that engine come in std, .020 and .030 over. Get a factory piston to match the other 2. An oversize piston will come with rings and weigh exactly what std pistons do. So you'll need two std ringsets for the other 2 pistons. Cyls like the middle one scuff when they overheat or suffer from lack of fuel/lubrication. When you had that middle carb apart and you pulled the main jet out-did you see any debris restricting the jet? That could cause it to run lean/hot. Fix it before the upper ring goes on that middle piston. The head gasket is still in place. How do the water passages look around the cyls?

 

[racerone]

Another classic example of why a compression test is the first step in trouble shooting.---I have to ask, does the hose for the pee indicator come off the side of the block or the top ?

 

[avisalem155]

I am going to call a shop (referred by my auto mechanic) tomorrow to see what kind of estimate he will give me just to bore the cylinders (top cylinder is lightly scored), or to bore and rebuild too. The water passages looked ok, however the head gasket needs to be replaced, it looked kind of rotted and had some pinholes in it around the middle cylinder. Also, on the head itself there seemed to be a build of of corrosion (white and powdery) that needs to be cleaned off. Even some of the screw holes that attach the head to the crankcase I had issues taking out and putting back in because of the corrosion. Probably had some water come through at some point. Also worth mentioning, the bottom cylinder looks to have been honed recently, so the previous owner must have had issues in the past.

I'll have to look and see where the water is exiting from on the block and get back to you.

Thanks
avi

 

[Faztbullet]

Bore it .020 and it will be fine...

 

[avisalem155]

Ok so I called the shop, the guy said if I bring him the block, he would bore and hone all 3 cylinders (he said might as well do all 3 if 2 of them need boring) for $150. Said it would take him a day or two, he said he's too busy to even rebuild the whole thing if I wanted him too. My manual should be coming before the end of the week. Do you guys think I can do the rebuild myself? and should I wait until he bores the block to order the rebuild kit ( I guess .020?), or order it now so once its done I can get started right away?

Thanks

 

[avisalem155]

Anyone??


Thanks