1987 Johnson GT 150 VRO

[blueghost]

I have problems with engine running very rich at idle. Compression is 95 psi on all cyls. VRO unit has been disconnected and plugged properly. <br />I have meticulously cleaned the carbs twice (no problems found). I have performed a "link and sync" (all was OK, no adjustments were necessary). Plugs all show to be equally wet (not dry) with moisture (fuel, not water).<br /><br />I do have a JohnnyRude manual, which I have tried most everything suggested. Unfortunately they do not discuss the "not using the VRO and using pre-mix" scenario.<br /><br />When cold and at idle, engine runs slightly rough (as most older 2 strokes do) and is very rich (lots of smoke) and often dies.<br /><br />When warmed up to normal operating temp for a few minutes, then slowed to idle, engine will usually die and must be restart with high idle lever pulled up (very frustrating at the ramp).<br /><br />I bought the boat and engine last year from a friend who had already been pre-mixing the fuel due to concerns and fears about the VRO system. He could not remember whether the engine developed this problem after removing the VRO or if it happened before the removal.<br /><br />Does anyone know if the idle orifice jets need to be resized after disconnecting the VRO? The ones in this engine are stamped with 30, which I assume is .030 inch, judging by the apparent visual size. Does anyone know if this is the proper size orifice jet for an elevation of 500 to 1000 ft above sea level? Any other suggestions? I have looked for all of the obvious problems. Help! Sorry for such a long post.

 

[rodbolt]

Re: 1987 Johnson GT 150 VRO

Hello<br /> is this engine a crossflow? I think it is. If it is does it have Plastic(minlon) fuel bowls?<br />let me know how many carbs it has 3 or 6 and about the plastic bowls

 

[Duck Loads]

Re: 1987 Johnson GT 150 VRO

This sounds like what happened to me this past summer with my '89 GT 150. The orifice sizes are in fact what they are marked. My Book calls for No 30 intermediate (0.030") and a No. 65c high speed (0.065") orifice. Is your throttle roller in good shape. the outer clear rubber cover on mine had deteriorated and fallen of. <br /><br />If you are sure your carbs are set up correctly (floats, sync & link, etc.) Thyen take a look at your recirc valves that are screwed into the manifold behind the carbs. You can see them, but you will have to remove the carbs to take them off.<br /><br />Mine were plugged up pretty bad. I used denatured alcohol and a tooth brush to clean the carbon off the screens. Get a syringe and suck alcohol through them to clean out the insides. New ones are still available, but they are about $10 each. Make sure they only flow in one direction. After this service, my GT 150 ran good as new. The $30 I paid for a factory workshop manual and this board is wortho mucho. <br /><br />Good luck,<br />Duck Loads

 

[blueghost]

Re: 1987 Johnson GT 150 VRO

Rodbolt,<br />It has three carbs with plastic bowls on them.

 

[blueghost]

Re: 1987 Johnson GT 150 VRO

Duck Loads,<br />I failed to include the fact that I have already replaced the recirc valves & checked the lines. I also already have a factory manual, but it hasn't helped much in the assesment of the problem yet.<br /><br />Are you still using the VRO or are you pre-mixing?

 

[OBJ]

Re: 1987 Johnson GT 150 VRO

Blueghost.....are the bowls leaking around the gasket area? Take a look and see. Squeeze the primer bulb up snug and keep slight pressure on it while you look at the bowls. The plastic bowls tend to warp after a while and leak.

 

[ob]

Re: 1987 Johnson GT 150 VRO

BlueGhost ,was the engine running fine with VRO connected and just started this after disabling?If in fact all plugs are wet with fuel after failed run attempt,I would surmise that your problem is leaky needle valve or floats set too high,or misfiring ignition.Have you checked for strong spark at cranking?Should jump an easy 7/16" with bright blue spark on each plug lead.<br /><br />Just for the record I think the 150 GT is a loop charged engine.<br /><br />As OBJ asked as well,Will the primer ball pump up and hold firm?

 

[Duck Loads]

Re: 1987 Johnson GT 150 VRO

That Gt 150 is a 90 deg crossflow motor. <br />Good job in replacing the recirc valves. <br /><br />Do this. Remove the air box cover from the carbs. Squeeze the fuel bulb good and tight while watching the carb throats. There are two brass carb vent tubes coming out straight out at you. Can you see any fuel coming out of, or just in, the vent tubes? If so, then your floats needles are not seating. <br /><br />Did you use new kits with new needles and seats and floats? My original needles looked perfectly fine, but they would stick open sometimes and closed sometimes. Any restriction in the idle air orifices? How about a pin hole in the fuel opump diaphram? This might allow fuel to be sucked into the crakcase. Just for fun, have you been through the ignition compoments checks in your manual?<br /><br />By the way, I also pre-mix my fuel/oil.<br /><br />Good luck,<br />Duck L.

 

[rodbolt]

Re: 1987 Johnson GT 150 VRO

Hello<br /> try this simple test. with the engine trimmed all the way down and at an idle start trimming it up. if the Idle speed and stability start improveing with a lot of trim up( keep water intakes in water) then I would pull the fuel bowls and place a straight edge across the back side at the fuel transfer area. these bowls do warp quite a bit and the symptoms are wont idle idles better if the engine is trimmed up. good luck and keep us posted. PS I have surfaced some but it is best to find metal bowls. that is another subject

 

[blueghost]

Re: 1987 Johnson GT 150 VRO

Outboard Jim,<br />It doesn't appear to be leaking around the bowls, however I'll recheck them to make sure.

 

[blueghost]

Re: 1987 Johnson GT 150 VRO

OB,<br />I'm not sure if this was a gradual problem or if it happened quickly. It has done this since I bought the boat and engine last year. The previous owner didn't recolect the time it took for the symptoms to occur.<br /><br />I did find out however that it had set (due to previous owners house burning and the rebuild of a new house) for almost 2 years.<br /><br />I'll recheck the spark for verification.<br /><br />I do have a couple of questions which I'll place here for any of you guys to explain. What is the definition of a "looper" or "loop charged" engine? What is a crossflow design? What are the differences?

 

[blueghost]

Re: 1987 Johnson GT 150 VRO

Duckloads,<br />Yes, I know which bowl vents your talking about. I'll do that and note the results. I did not replace the needle and seats when I checked the carbs. I checked as much of the ignition sys as possible with the limited equipment that I have.<br /><br />All of the idle passages and orifices are clear and clean. I thought about the pump diaphragm some time back so I pulled slight vacuum on pump and it appeared to hold, so I don't think there is a problem there.<br /><br />On my reply back to OB I asked a couple of questions, which may answer this one. Do the three carbs serve the individual sets of cylinders or is there internal cross-connection behind the reed valves?

 

[blueghost]

Re: 1987 Johnson GT 150 VRO

Rodbolt,<br />I'll try tilting the engine. I have heard of this before, but I guess I really haven't placed my attention on it (when I get to the lake I just kinda loose my focus and gotta go fish). If the bowls are the problem, are there metal aftermarket bowls or OEM bowls available?

 

[Duck Loads]

Re: 1987 Johnson GT 150 VRO

Well B'ghost man,<br /><br />When you get this thing figures out, you'll know nore about that motor then you thought you ever would (or wanted to). <br /><br />My float bowls are also plastic. When I rebuilt mine, They leaked like a sieve. I had to take them back apart and resurface them. I used 120 grit paper on a thick plate of glass, and it worked ok. I understand that the replacements are metal. Perhaps next time.<br /><br />It is my understanding that one carb throat feeds one cylinder. I might be wrong, but looking at the exploded view of the powerhead, it looks like both carb throats are separated in the intake manifold.<br /><br />Good luck,<br />Duck L.

 

[blueghost]

Re: 1987 Johnson GT 150 VRO

Duck Loads,<br /><br />Maybe I'm missing something, but if the bowls were warped, wouldn't that allow air in or fuel out? If fuel is escaping that shouldn't load the engine at idle, and if air is getting into the bowl, it would just vent out, not effecting it at idle?<br /><br />I haven't had a chance to work on it the last few days, but I plan too this week in the evenings.

 

[Duck Loads]

Re: 1987 Johnson GT 150 VRO

I do believe that if the float bowls are warped and leaking then that's all you've got. Poof, You have a fuel leak. I don't think you will have any drivability problems until the thing catches fire and goes ka-boom ( oh shoot). <br /><br />When you get a chance, look at the brass float bowl vents while you hold pressure on the fuel bulb. I'm still hoping that you're float needle & seats aren't sealing letting fuel out the vents. Fun ain't it . I hope to see a positive post from you in a few days.<br /><br />Good luck,<br />Duck L.

 

[kclark1963]

Re: 1987 Johnson GT 150 VRO

Well I can tell you that on my 2000 Jonny 115 I had that problem and it didn't leak fuel but did cause a problem on that cylinder though i believe it was a starve problem if i remember right. Hope this helps <br /><br />Kevin

 

[rodbolt]

Re: 1987 Johnson GT 150 VRO

Hello<br /> yes one throat feeds one cylinder. and yes metal bowl kits are avalible but try to find a used set of bowls from an older v4/v6 crossflow.the jet physical locatin changed some but if you put all your old jets in a diffent bowl the minor relocation of the access to the jet does not matter. the new bowl kits will require you to either rethread the mainjet holes or buy all new jets.I have seen numerous bowls leak fuel to the bowl area bypassing the needle valve and never leak a drop outside.it may be time for a kit in each carb . the differnce in a looper and a crossflow is the metod of incoming air/fuel delivery to the intake ports in the cylinder walls.<br /> cross flow engines can be ID'd by the transfer port covers, one at each cyl on the outsides of the cyl banks each cover is held on by 6 bolts. <br /> good luck and keep us posted

 

[blueghost]

Re: 1987 Johnson GT 150 VRO

Well guys, (Duck Loads, Outboard Jim, OB, Rodbolt, Kclark) I am finally back. I have been busy with a couple of weddings (one of which was my daughters), working, and several other projects. I took my carbs off the engine last night, disassembled them today, and have found that the bowls are warped approximately .020", maybe more. I plan to check on new ones tomorrow, but have a fish trip planned Saturday, so just in case I am in the process of sanding them, which I think will work until I can get some new ones in. Hopefully this corrects my problems. I'll keep you posted.