86 Johnson 150 stumble

[wtp]

I had a whole bunch of problems with this 150. Long story short I tore the whole motor down and put all new power head gaskets in. New carb kits and jets. New valves below the carbs (can't remember what there called) New coils, power packs and stator. New voltage regultor and also plugs. Everything is OEM except stator and power packs. Reed valves are better then what the manual says is acceptable. Compression is good. Runs great at anything over idle. Seems to idle good but take off stumbles alittle. Sometimes it stumbles just for a second or two and planes right out. sometimes it will stumble for 4 to 6 sec and takes right off. It's weird but runs great at mid and top end. I know your gonna ask so I'll tell you. I've been through these carbs a total of 5 times. Every hole is spotless. jets are new. carb floats are set to level when held up side down and 7/8 drop when turned over. VRO has been removed and 2 pumps installed. All new fuel lines. New primer bulb. I'm not completly certain but I think the link n sync is right. Starts good, runs good but just that darn take off. Running QL16V plugs. Was told to try have the timing advance a couple degrees before the throttle plates start to open. That did nothing and is why I'm thinking fuel. Out of ideas.

 

[emdsapmgr]

Re: 86 Johnson 150 stumble

Did you replace the stock metal reeds with composite reeds? Usually the composite reeds come with instructions to change the carb jetting slightly since they will flow more air than stock metal reeds. When the engine starts to stumble just off idle, try pushing in on the key. That will richen up the fuel mixture somewhat. If the engine picks right up when priming with the key, then the engine is probably running lean at just over idle. Have a look at the mid jets.

 

[wtp]

Re: 86 Johnson 150 stumble

reeds are stock. All the jets are new oem replacements. I will try push in the prime this weekend when I'm out. I think it might be running rich but will for surely give it a try this weekend. The bad part is these carbs have no adjustments.

 

[wtp]

Re: 86 Johnson 150 stumble

anybody?

 

[emdsapmgr]

Re: 86 Johnson 150 stumble

Any reason your replaced the jets? Usually they do not require replacement, just clean and reuse. OMC made two 150's that year, the base 150 and the high performance 150S. Which model is the one you have? Did you rejet to the same factory specs for your model? Are you running stock heads?

 

[wtp]

Re: 86 Johnson 150 stumble

Any reason your replaced the jets? Usually they do not require replacement, just clean and reuse. OMC made two 150's that year, the base 150 and the high performance 150S. Which model is the one you have? Did you rejet to the same factory specs for your model? Are you running stock heads?

I was told that over time the jet holes can get over sized so I replaced them when I put the oem kit in. I have the S model and replaced them with what is suppose to be in there. Mine also were kinda crappy looking. You can tell they were removed before. Yes they are stock heads.

 

[emdsapmgr]

Re: 86 Johnson 150 stumble

The GT model is a nice engine. When you went through the carbs, did you spray an aerosol carb cleaner through each passageway before you reinstalled the jets? Did you compare the spray coming out of the hole of one carb with the spary coming out of the same hole of another carb? Not unusual for dried fuel to clog/restrict a passageway-you can't see inside the passageway, so it's difficult to tell.

 

[wtp]

Re: 86 Johnson 150 stumble

they soaked over night in a bucket of carb cleaner and blew 120psi through every hole in that carb. even the ones under them 2 aluminum plugs.

 

[wtp]

Re: 86 Johnson 150 stumble

would it hurt anything if I tried it with only one fuel pump. Right now i'm running 2 pumps like whats on the 1983 150hp

 

[shawn1]

Re: 86 Johnson 150 stumble

I have the same problem with my gt 150.It starts great and runs great till about three thousand then spits and bogs till it warms up then runs great.does it every time.Whats the cause for this?Does it have to warm up.Motor runs great when its warm..Help

 

[wtp]

Re: 86 Johnson 150 stumble

mine is only on take off so I'm guessing it sputters until maybe 1500rpm.

 

[wtp]

Re: 86 Johnson 150 stumble

I dropped to 1 fuel pump and it seems to be pretty good. Very slight sputter now, i mean slight. I think I'll just leave it now. I'll use it for the rest of the year and fiddle a little more with it in the spring. I'm almost out of time to enjoy it this year.