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1998 Johnson 150, Still having issues

D

Davem02

Contributing Member
I just want to first say thank you to those that posted on my other threads with tips and suggestions.

After replacing the following this weekend, the motor still will not idle very well, and I have to push the ignition key in to load it on the trailer.

Replaced the following:
Both gaskets from Manifold's to power head
Both Gaskets (Spagetti type) from throttle bodies to manifold
Carb side cover gaskets
Carb to throttle body gaskets.
12 O ring gaskets on fuel manifold into the throttle bodies
2 O rings on VRO elbow into fuel bracket
2 lower fuel lines going from VRO into fuel bracket
Fuel bracket
New needle and seat in vapor separator, adjusted float according to manual.
Torqued all bolts and screws according to manual
Adjusted idle needles 5 turns from seated position, according to manual. Adjusted another half turn counter clockwise at the lake. Engine still sneezes (not as much as before) and will run a little longer in idle, than before.

That is what I've done thus far. WOT runs great. Idle and idle speed suck. It does not use as much oil as it was, and certainly not smoking as bad as it was before now either. So that at least changed. Unless I can figure this issue out myself, I guess I'm gonna have to break loose $2200 to have a professional fix it. If it can be fixed. I'm at a loss here, & very frustrated.
 
Dave.... Having retired in 1991, I'm not acquainted with the design of your 1998 model 150. However, I do want to mention about a OMC V6 150 model that was manufactured (I think) back in the 1980's. There was a ever so slight warpage between the intake manifold and the crankcase that resulted in a impossibility to have the engine idle properly. OMC came out with a cure in the form of a bulletin.

The cure was simply to double gasket the area containing the warpage. I don't remember how many engines I installed two gaskets between the manifold and the crankcase, but I do remember that it resulted in a excellent idle.
 
Totally different mota....no need to double gasket/s. Need to get a OEM manual and set the carbs in the water as described as 5 turns is just a starting point.
 
Okay, I did adjust them out to 5 1/2 turns while in the water with no result, but I'll take it back to the lake and adjust again. The issue I was having today was that the damn motor wouldn't stay running long enough for me to adjust the needles to really notice a difference. So how far out should I adjust before it becomes apparent that those aren't the issue? I know the starboard side upper most carb before I started all this was out 6 3/4 turns from seated position. I do have the OEM manual.
 
After speaking with a Johnson mechanic, he suspects the VRO. I've kinda felt this was the issue as well. Of course there are no 100% guarantee that this will cure the problem. I'm still going to take it back to the lake and try adjusting the idle needles out some more. I'm also going to use some decarb stuff I got at my johnson dealer. It goes into the fuel tank and its a shock treatment. I bought new plugs for after this is completed. I've also ordered a new VRO. If these steps clear the issue, I'll return the new VRO. If not, I'll install the new VRO and see what that does.
 
I still think you have a restricted/blocked fuel delivery regarding the idle circuits in the carb system. This includes the carbs AND the throttle bodies.
I do not see on this post that you cleaned the throttle bodies. How many holes were there down in the calibration pocket of the throttle bodies?
How big were the holes? They are VERY VERY easy to overlook. On my V6 looper, there are 5 holes. Not sure on your model.

Another place you could have idle fuel restriction is in the small brass tube that extends from the carb upper down into the bowls. It is a small brass tube that tapers at the top to a much smaller diameter. Those tubes are the source of all the idle fuel the engine pulls.

FWIW, I have had the EXACT same symptoms you describe on the V6 loopers I have worked on. My own included.
 
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What other trouble shooting has been done ?-----------Compression tested ?------------And does spark jump a gap of 3/8" or more on each lead ?
 
There were three holes down inside, & one on the side from what I remember. I shined a light up through the throttle body from the other side & could see clearly all three holes. I used a little carb cleaner on the other one. They appeared to be clear.

A compression test was done. There was one cylinder that was lower than all the rest, I believe it was cyl 6. Highest was 130 lowest was 115
I'm going to Autozone tomorrow and getting a spark test board to make sure I'm getting proper spark.
 
Daselbee, I cleaned the throttle bodies pretty good. I removed the small metal plates and gaskets on the side of the throttle bodies. I shined a light and could clearly see through all the small holes down inside. I sprayed carb cleaner through those and the hole on the side wall that goes into where the butterfly is. All appears to be clear there. When I rebuilt the carbs, and sprayed carb cleaner in those brass tubes, and observed it coming out the other end. There didn't appear to be any blockage.

Today I added Yamalube Ring Free to my fuel tank, not quite enough to do a shock treatment, but close. I took it to the lake and adjusted the idle needles out some more. I'm at 6 1/2 turns now. The motor did seem to idle better, but is hoving between 700-1000rpms idle. The motor wanted to die once put in gear unless I gave it more throttle. Also noticed that right at take off, the motor seems to be running rough & there is a very slight hesitation. WOT, runs awesome. Its also smoking more than I feel it should (could be due to the Ring Free though). Autozone didn't have any decent spark testers. Can anyone recommend a certain brand or type? I guess I could just use a paperclip or something like that & ground it on the motor?? I have a new VRO coming, so I'll wait until I run all the Ring Free out to install it. I'm also going to take it out again tomorrow and adjust the idle needles out some more.
 
One other thing I forgot to note. I pumped the fuel bulb up yesterday after I got back from the lake, just to see if there were any visible leaks. There were none. I went to work & when I got back after midnight I checked the bulb. It was still hard, no leak down.
 
OK Dave, my last post on this thread. I will back off.

You say you saw one hole the passes thru to the throttle bore, right at the butterfly.

I have 5 holes like you describe on my 200 looper. I find it nearly impossible that a 150 only has one hole that goes thru to the throttle bore.

I suggest you look again. If all is clear, so be it. I think you missed some very tiny holes.

Good luck.
 
No need to back off, I may have indeed missed something in there. As much of a pain the the butt it is to remove all the carbs, I'll do it just to make sure all the holes are clear. Installing new VRO tomorrow too. Thanks for the help.
 
Dave, just pull off one side plate on the TB. Get a good flashlight and look in there. All the holes I am referring to pass thru from that pocket into the throttle bore. They go thru right at the butterfly location. It should be easy to see if you missed some holes. They are very very tiny, and if clogged, are very difficult to even see.

If you see the holes I am talking about, then you can decide whether you need to pull the carbs again.
 
Who has a 150 or 175 throttle body that could inspect the calibration pocket under the metal plate and verify the number of holes?

Someone does......
 
Thank you, I will take a looksee at the starboard side throttle body. Those are easy to get to. I replaced the VRO today. Definite improvement on the way it runs. Doesn't stall while idling, doesn't stall while loading on trailer. However, it still wants to stall when put in gear and idle speed unless I give it more throttle. Doesn't smoke as much & doesn't appear to be using too much oil. I did adjust idle needles out to 7 1/2 turns. Maybe a lil too much?
 
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