Johnson 150 won't run faster than idle speed

[sullivanjm]

I have a 93 Johnson 150 that I use about every 4-5 weeks. Last time I took it out, I had a loose battery cable, so when I went out yesterday, it had been about 2 months since I had the motor running. It usually takes a few tries to crank it since I don't use it every week, but once it cranks, I have no problems. Yesterday was different!<br /><br />I can crank the motor, and if I don't put it in gear, I can idle it up to over 4000-5000 RPMs. However, when I put it in gear, it will only run at about 1500 RPMs, and won't get up any speed. After running at 1500 RPMs (in circles trying to warm the engine up) for about 5 minutes, it will die and I have to repump the fuel bulb and wait a minute or two to restart it (like it's flooded or something). I'm not a mechanic, but have the manual and have basic engine knowledge. Any suggestions for a "quick fix" try before I sink money in a mechanic to troubleshoot this?<br /><br />Thanks!

 

[JB]

Re: Johnson 150 won't run faster than idle speed

Ahoy, SullivanJM. Sounds to me like you are running on 2 to 4 cylinders on that V6, which suggests that you have lost a carb or a powerpack.<br /><br />You can ID a carb problem by spraying WD-40 in to the throats while the engine is misbehaving. If the cylinders come on, that carb is not performing.<br /><br />To ID an ignition problem, the best method is an ignition tester. Your V6 has two, independent systems, one for each bank. If you determine that one bank, or one cylinder is not getting spark, you can ID the bad part by substitution.<br /><br />Good Luck!<br /><br />Red sky at night. . .<br />JB

 

[DJ]

Re: Johnson 150 won't run faster than idle speed

Sullivajm,<br /><br />It's fuel related. Did you just fuel it before this occurred? If so, I would be suspect of the fuel you got.<br /><br />If not, borrow a seperate six gallon tank and a fuel hose. Try running it with that. If it runs OK-you know you've got a problem with something between the fuel tank and the engine.

 

[Backlash]

Re: Johnson 150 won't run faster than idle speed

Hey Sullivanjm,<br />Like JB says.....It's hard to "hear" a dropped cylinder unless the engine is under load. It might idle just fine on 4 cylinders but can't make power on 4. <br />Backlash

 

[sullivanjm]

Re: Johnson 150 won't run faster than idle speed

Great feedback so far. Thanks.<br /><br />Here's the latest. Just went and put it in the water and set it at 3000 rpms. When pulling 3 of the 6 spark plugs, the RPMs didn't drop, but I still had a spark. (So it shouldn't be the power packs.) I had the compression checked and they all checked out at 100-105. The fuel is about 2 months old, but the tank is completely full, where I keep it.<br /><br />So...looks like the carburator(s). Bad thing is there are 6 of them. My next step is to try to clean them instead of pay the $400 to have them rebuilt. Any more comments or suggestions?

 

[sullivanjm]

Re: Johnson 150 won't run faster than idle speed

OK - the problem is now fixed. Before I explain how, I want to say THANKS for those who helped. This is an awesome web site, and although I'm a first time user, I'm a dot com executive, and this is a site that provides some real value to boaters. KUDOS to iboats.com!!<br /><br />I am not a mechanic, but I called a friend and he walked me through a very easy procedure for cleaning the carburators. If you remove the sound muffler, you have easy access to all 6 carbs. On the bottom of each one is a screw that drains the lower carb pan. Take each of these off. Pump the fuel bulb and if gas comes out the hole where the screw was, that carb is NOT blocked. You can replace those screws. On the blocked (or gummed ones), get a can of Berryman's B-12 Carb Cleaner, and spray it into that lower pan. (I used a regular drinking straw as a funnel, which fit perfectly in the hole.) Leave the straw and fluid in the lower pan for a few minutes. The B12 will break down the gum in the carbs, and clean them out. Pump the fuel bulb again, and you'll see if one of the carbs breaks loose, because fuel will start coming through that lower pan again. Finally, if you still have one or more stuck (which I did), you can take a screwdriver and tap on the plastic tube that feeds into each carb from the fuel line. Tap on the tube where it enters the gummed carb while you are pumping on the bulb (and have pressure on it) until it breaks loose. It will take 10-20 taps, but this is how I broke lose 2 of the 3 of mine that were stuck. It was also recommended to me to go ahead an add a can of Berryman's B12 (the pour can instead of the spray can) directly to the gas tank and run the boat for while to finish cleaning out those gummed carbs. That's about it. Hope this helps someone out there.<br /><br />Good luck fishing!

 

[johnkc]

Re: Johnson 150 won't run faster than idle speed

what is the carb cleaner going to do to the plastic and rubber parts in the fuel system ,the engines that i work on have metal carbs.

 

[MGuckin]

Re: Johnson 150 won't run faster than idle speed

Glad that trick worked for you. I used that for automotive applications. Unfortunetly, outboards are a bit different. High speed jets (sealed on mine) and low (idle) speed orifice. Sounds like your floats or needle valve were stuck and it worked.<br />Metal carb is new to me. Those that I have seen are white metal, lead/aluminum alloy or all out aluminum and maybe some brass seats. <br />I am not saying that there isn't, but I have never used a carb cleaner or solvent that damages rubber or plastic but it might tarnish the carb casting.<br />Edited: and or blemish the finish.<br />But I dismantle them first usually. <br />

 

[MERCMAN]

Re: Johnson 150 won't run faster than idle speed

WHAT WILL THE CARB CLEANER TO THE GASKETS YOU ASK. IT WILL EAT THE RUBBER BOWL GASKETS AND WILL DILUTE THE OIL AND WASH THE OIL OF OF THE BEARINGS.

 

[johnkc]

Re: Johnson 150 won't run faster than idle speed

metal carb -carb made of metal wether it be white metal, lead/aluminum alloy,all aluminum,or brass. not made of plastic/space age material. sometimes i don't explain my self well <br />and therefore won't it eat the fuel pump diaphragm,and the primer bulb, and the fuel hoses?

 

[jungnim2]

Re: Johnson 150 won't run faster than idle speed

no hi have a v6 loper the have 6 plastic carbs the gung up you need to put a valve on the gas line to stop the gas wen you store the motor let him run out of gas

 

[petryshyn]

Re: Johnson 150 won't run faster than idle speed

The automotive carb cleaner in an aerosol can is much the same as lacquer thinner. In my experience, it will viciously attack non-baked painted finishes, varnish, magnetic wire insulation, grease, rubber, plastic, nylon, styrofoam and other synthetic products. It is meant mostly for outside cosmetic cleaning and throttle bore cleaning on 4-strokers. The stuff is wonderfull when used apropriately, but you'll suffer its wrath if you spray sensitive components!! <br /><br />my .01 cents worth.....

 

[MERCMAN]

Re: Johnson 150 won't run faster than idle speed

IT IS RECCOMENDED THAT YOU LEAVE FUEL IN CARBS AND TREAT FUEL BECAUSE IF YOU RUN THE FUEL OUT OF CARBS IT IS NOT GOING TO PICKUP ALL THE FUEL FROM BOWLS THEREFORE CAUSING THE REST OF THE FUEL TO EVAPORATE AND LEAVING THE OIL TO TARNISH THE BOWLS THE MAIN JETS AND THE IDLE AND OFF-IDLE TUBES IN THESE PATICULIAR MAYLAR CARBS.

 

[clanton]

Re: Johnson 150 won't run faster than idle speed

Removing the float bowl drain screw, pumping the primer bulb,until fuel drains out of the drain, DOES NOT clear the main jet. This method only clears the float needle and seat.<br />Filling the float bowl with carb cleaner will not always desolve the varnsh and trash, completely where it will pass thru the main jet, sometimes the trash will float around inside the bowl, and later plug the jet,if you are running 5000 rpms whens it pulgs the jet, lean condition and burnt cylinder, BUT what every method you choose and it works for you use it.