'93 Johnson won't run

[gryzz]

I?m going to layout my whole story so this might get a bit long.

I?ve got a ?93 Johnson 40hp, electric start, with the VRO system disabled. I disabled the VRO 3 years ago because out of the blue I would get the No Oil warning signal. Happened a couple of times before I disabled it.

So, last year at about this time of year I took the boat out of storage and promptly burned down the lower unit, either a severe leak or a stupid mistake by me. At that point I put the boat away and started to look for a new motor or boat. About a month ago I found a lower unit for it and decided to just put that on for now.

Lower unit went on and works fine but the engine is not doing so great. I didn?t stabil the gas or anything and it sat for a year. I took it out once and the engine ran terrible, but it did run. The guy who put the lower unit on for me said it ran rough for him also and I probably needed some carb work.

I brought it back to him to have the carbs cleaned up. He checked the compression at that time and found it was 125 and 105. He said it wasn?t good but I could probably run it like this if I wanted to. I don?t feel like putting another $1200 into this motor at this time and I figured the compression has been bad for awhile so I decided to just try it this way.

He cleaned the carbs and replaced all of the gaskets, saying they were in terrible shape. He said the internal components ? float, float valve, etc. were in good shape and he didn?t replace.

I took it out last weekend, fired it up with a new tank and new gas and it ran pretty well for about 3 minutes. 2 minutes of trolling then one wide open and it bogged down. Messed around with it at the dock for the remainder of the weekend and couldn?t get it to run right. I could keep it running with the primer button but otherwise it would starve for gas. I had an old fuel hose with a bad check valve so I purchased a new one of those and a new fuel filter. Didn?t help.

I then brought it home and did some work in the driveway. I pulled off the air intake and pulled the drain plugs out of the carbs. Both bowls had plenty of gas in them and leaked gas when I pumped the bulb on the hose. I did my best to blow out the jets behind those plugs and could see fluid entering the carb. The lower one seemed like it may have been a bit plugged but I couldn?t tell for sure.

I put it back together and fired it up, ran like a top. Didn?t need the primer button once it warmed up and it would idle down quite nicely.

Yesterday I took it out and it ran fine, for about 3 minutes. 2 minutes at idle then a minute or so at wide open and it bogged down again. It acted just like it did last weekend. Won?t idle or run at a higher speed by itself, but I can keep it running with the primer button


So, there?s the whole story, any help at all would be greatly, greatly appreciated.

Thanks,
Joe

 

[Dhadley]

Re: '93 Johnson won't run

Energizing the primer puts fuel into the system by by-passing the carbs. Not sure what 3 minutes has to do with anything but I'd sure start with another look at the carbs.

 

[tashasdaddy]

Re: '93 Johnson won't run

I have the same motor. do you have a fuel filter in line. also this, sounds like high speeds are clogging. or you are loosing spark on one cylinder. check your spark right after it bogs.
it will run on one cylinder. http://forums.iboats.com/showthread.php?t=244013

 

[gryzz]

Re: '93 Johnson won't run

Thanks for the quick responses.

Can't say it was exactly 3 minutes, I was just trying to make the point that it ran for about the same length both times.

Yes, it is an inline fuel filter that I replaced.

I checked the spark in the midst of one of it's bog down sessions and had good strong spark to each plug.

If I go back into the carbs and can get it to run correctly, I'd assume that I have some junk floating around in between the fuel filter and the carbs that is coming loose and clogging things up. Can I put an additional fuel filter in right in front of the carbs to weed out any sediment I might have floating around in the system?

 

[GaryWPB]

Re: '93 Johnson won't run

Sounds to me like possibly it is running good until all the fuel is out of the carb bowl. I would check the following. 1. Make sure that the fuel tank is not creating a vacuum and not making it hard to get the fuel from the tank to the carb. Open the fuel cap when you have the problem and see if it has a suction. 2. Quite possibly the Float needle valve is not opeining or has contamination reducing the flow of fuel into the bowl. It would seem odd that if that was the problem you would hear one of the 2 cylinders drop off before the other . 3. Try pumping the ball if you have not already when having the problem. however if when you push the primer it continues to run that would tell me that there is fuel pressure at least to the carborators as the primer sorce I believe comes from the same manafold (splitter). 4. If you are able to pull the drain plugs out of each carb when you are having this problem and verify that there is in fact a sufficent amount to come out then you could rule out all the above potential problems. I have had problems where the float valve would stick in the closed position and could only get the motor to run on one clylinder. Even tapping on the bowl with a metallic tool did not free the float valve (Needle & Seat) I think possibly the oil mixed in with the fuel causes it to stick. ( just my thoughts) My metal tank was not vented and until I drilled a very minute hole in the cap to allow air to go in I was having float sticking closed numerous times.

 

[gryzz]

Re: '93 Johnson won't run

Well, i thought i had eliminated the possibility of the float valve sticking but it seems like that is the problem. I fired it up in the driveway last night and it was still running poorly. I drained both carbs and noticed that the upper didn't have much gas in it. I then plugged the lower one and pumped the bulb. No gas came out of the upper carb and the bulb hardened up. I whacked it a couple times with a rubber mallet, the valve opened up and gas poured out.

The next question i have is about the tank venting. I have a brand new tank and fuel line but i'm wondering if this could still be the problem. Is there an easy way to check that out of the water?

Thanks for all the help, it feels good to know what it is.

 

[gryzz]

Re: '93 Johnson won't run

I replaced the needle and seat in the upper float valve and that seems to be working fine now. It runs like a top at full speed but getting there can be interesting. Sometimes it idles decent, sometimes not at all, and always seems to bog when I power it up. But once it catches it runs well.

The mechanic that cleaned my carbs and replaced the needle and seat informed me (beforehand) that my compression is not good. 95 and 125, I think. He said, with clean carbs and good gas I could probably limp it along like this but it wouldn't run properly.

If I don't want to rebuild it, am I just stuck with what I have now; bad idle and bogging take off, or do I have other options?

Thanks again.