Smokey - 1980 Johnson 4.5 HP

[tpenfield]

I just picked up a 1980 Johnson 4.5 HP ( model J5RLCSS ) and have run it a few times in a barrel. Probably a total of 1 hour of running. The engine runs well, idles well, shifts well , etc. The only thing I noticed is that it puts out a tremendous amount of smoke from the 2-cycle fuel mix. I am using a 50:1 mix, same as what I run in my Mercury 7.5 hp,( actually poured the fuel from the Mercury tank) but the little Johnson makes about 4-5 times the smoke.

It will be great for clearing the yard of Mosquitos come spring time, but I am wondering if that is a johnnyrude trait, or something I can adjust? I checked the plugs and they are clean, monkeyed with the fuel mixture knob, etc. to no avail., choke is not engaged, etc.

Thanks for any insight on this, I am more familiar with Merc's than Johnson/Evinrudes.

 

[oldboat1]

Had an Evinrude 4 Deluxe that ran well ('90 I think). If you haven't done so, should replace the impeller as a first step. 50:1 is the mix -- think I would be sure first that the fuel and oil is fresh (and, I guess, that the mix is right). Running in a barrel is a little smokier, but not all that much. If it's running well, might just let it idle for a while in the barrel or on the boat. May need to be run a bit to clear itself out.

 

[racerone]

50:1 is the mix.----Perhaps have a look at the fuel pump diaphragm for a pin hole.---Should not smoke more than any other motor.

 

[Crosbyman]

tried cleaning it up a bit with seafoam or BRP engine cleaner..

 

[tpenfield]

Here are a couple of videos that give a pretty good comparison of the amount of smoke from the 2 engines ( Johnson vs. Mercury)

This is the Johnson, not my engine, but the smoke is about the same.

This is my Mercury.

The engines are running fuel from the same tank mixed at 50:1

I will try the sea foam . . . might be a bit of carbon build up in the cylinders holding onto too much oil.

 

[oldboat1]

not nearly enough water in the Johnson video -- would probably explain most of the smoke in that case. Agree, Merc seems about right (but think could use a bit deeper water there too). Think I would let your Johnson run a little bit before sea foam. (just MO). Is your motor similar to the one in the video, or does yours have an integral tank? (thinking it might be more likely to have some old fuel or debris in the integral tank, but separate tank susceptible too of course.)

 

[tpenfield]

Thanks guys, I'll try to get a video of my engine . . . If the engine is not getting enough cooling water would it smoke due to running hot? I was getting a good stream of water out of the telltale.

 

[oldboat1]

well, smoke at that point (i.e., from hot running) might be too late. But guess the smoke in the pic is exhaust that would normally be under water.

edit. really need to replace the impeller as a first step. Run it with the cover off to check on temp (about 130F or so on top of head -- can hold the heel of your hand on it for a few seconds).

 

[TN-25]

I wonder if the Johnson might be running richer than it might need to be. I'm thinking carb cleaning and adjustment. Was the choke left on inadvertently? Also a leaking head gasket or exhaust bypass cover could also allow steam to be thrown into the exhaust. I'm just thinking of obscure possible explanations.

 

[tpenfield]

Update:

I had some time to run the engine some more today and do some adjustments. I soaked the cylinders with seafoam for a few hours to help with the carbon buildup. It is definitely running rich and I was able to lean it out to a point where the smoke was at a more normal level. However, the engine would not stay running consistently with that setting.

After a little more diagnostics, it looks like the carburetor needs to be rebuilt or replaced. It seems that the float valve in the carb is not working as fuel just spills from the carb and even does it when the engine is idling. So, I plan to take the carb off and either rebuild or replace.

Disconnecting the linkages looks to be a little tricky, particularly the combo choke & fuel valve knob. Any tips on that?

 

[tpenfield]

Update:

I got the carburetor off the engine . . . just needed some persuasion. After taking it apart, it looks OK. The float floats the valve looks OK

One thing that seems odd, is that according to the parts diagram, there is supposed to be an inline fuel filter between the fuel tank and the carb, but there is not one on this engine. So, I am wondering if the carb is getting gunked up with minute debris that a filter should catch.

 

[tpenfield]

Question:

This engine has the internal tank rather than the auxiliary tank that larger outboards have. So, presumably the fuel flows to the carb based on gravity feed. However, I noticed a hose that connects from the crank case to a fitting on the carburetor. It connects right next to the fuel line fitting.

Generally, crankcase vacuum/pressure is used for fuel pumps, but this engine does not have a fuel pump, since it is an internal tank.

??? What would this hose between the crank case and the carburetor be for ? ? ?

I am wondering if it may be part of the rich mixture problem if some how fuel is being sucked into the crank case. :noidea:

EDIT: the hose in question is called a 'pulse hose' on the parts diagram.

 

[racerone]

But, but ---It does have a very simple bladder ( fuel pump ) on the carburetor.-You may not recognize it as a fuel pumping device !

 

[tpenfield]

But, but ---It does have a very simple bladder ( fuel pump ) on the carburetor.-You may not recognize it as a fuel pumping device !

Yup, just did a little reading and discovered that, so it provides a basic pumping action as well as having gravity flow. The fuel line was connected to the fitting where the bladder goes. The pulse line was on the one right next to it. Assuming that is right. . . If an o-ring seal were bad, I am wondering if fuel would get sucked up the pulse line?

Thanks for any additional insight.

 

[tpenfield]

Also, thinking that maybe the fuel line and the pulse line were reversed on the fittings at the carb :noidea: Of course, my recollection of how they were connected my be wrong.

I'll have to take a look at the bladder piece tonight. Just want to get the carb working properly before I try to tune it, etc.

 

[oldboat1]

Doesn't the 4.5 come with the option of using either the integral tank or an auxiliary tank? Not sure about carb plumbing, but thinking separate carb inlet for each system, with a fuel shutoff for the built in tank. If dual use, will have a tank inlet on the cowling, and a fuel pump. (If dual use, try an auxiliary tank, shutting off the the switch for the integral tank -- shut off switch at carb, I believe.) On the old gravity flow motors, the shut off switch was a potential source for clogging.

Also, there should be an inline filter between the integral tank and the carb. The filter could be plugged.

edit. -- although see fuel restriction isn't the issue in your case -- maybe contamination in the case of a dirty filter(?)

 

[tpenfield]

This is the 'Integral Tank' model, so no adapter for an auxiliary tank. The aux tank model also has a 'diaphragm' fuel pump rather than a 'bladder' pump. Also no 'inline' fuel filter between tank and carb, so I ordered one last night. that may be part of the problem, just not sure at this point.

I did spend some time 'googling' "bladder pumps" and found some interesting info. Basically, it is a 1950/1960's invention to provide fuel flow for small engines that may become inverted or not be able to use gravity feed for fuel flow. So, you got the 'bladder' (that expands and contracts via the crankcase pressure) captured inside a larger tube (fuel line) and a couple of check valves to insure 1-way flow.

I am just not seeing yet how this all works in the Johnson/Evinrude carburetor. I only see 1 check valve, but maybe I'll find a second one when I take the fuel line fitting off and check the bladder.

 

[oldboat1]

Hmmm. I have a '66 Yachtwin with both an integral tank and an auxiliary tank connector. As I recall, there is a switchover valve running to the carb. Not an option on the '80 4.5, apparently.

All of the 1980 4.5 models seem to have one carb (the one with the bladder at the carb inlet, like you have) -- which seems a little strange to me. Maybe the bladder was simply removed on models set up with the auxiliary tank option. Wouldn't run with both the bladder and a fuel pump, right?

I wonder if your motor would run OK without the bladder at the carb inlet (i.e., strictly gravity flow). If no smoking, would probably indicate the bladder is faulty(?) Maybe you already tried that.

(btw, also curious if there was no filter between the tank and the carb -- just going by parts diagrams. Maybe a PO removed it, unsuccessfully attempting to fix the smoking problem you are having.)

 

[tpenfield]

I caught up on my photos and videos this evening . . . So, here is the motor running at a high idle and smoking quite a bit.

I was able to lean out the mixture to reduce the smoke, but the engine would run consistently at this setting.

So, I'd like to get the carb sorted out and then take another run at setting the mixture.

Here is a picture of the carburetor and the bladder. It is in good shape, no cracks/holes, etc.


In looking at the design, it looks like the fuel passes around the bladder and into the carb bowl. It seems that this design may not need or use 2 check valves . . . perhaps it relies on expansion of the bladder to prevent backflow.

I think my next steps are to install the fuel filter once it arrives. I cleaned out all of the ports and channels in the carb with a thin wire. So, maybe with clean fuel, the carb will work better. I can see if the engine runs OK with just gravity feed by plugging the 'pulse' tube.

 

[oldboat1]

first look opinion is that it's not overly smokey -- high rpms may be producing the effect in the barrel. If mine, I would try to see how low it would idle (and increase the water level....)

seems to run well as is. Think I would try to dial in the mix (as suggested) for a slow idle, and let it run a bit on the fresh fuel. Monitor temp. Seems to be pumping fine. (But will admit, would like to see if it would operate with pure gravity flow -- pulse blocked off, like you suggest.)

Think there is a possibility that carb would work as is with an auxiliary tank? Can't believe that bladder would be sufficient, but maybe after fuel is flowing.

(btw -- thanks for the pics.)

Not suggesting going to an aux tank -- just curious about the carb. By the way, if blocking off pulse feed to test, thinking you would want to block both the hose and the carb opening.