150 johnson stalls

[Stinkbait]

Got a 89 STL150 V6 Johnson, runs great at first then the rpm drops off. Have replace plugs, gas lines from the tanks to the motor up to the VRO. Has been decarbed. Carburetors have been tuned. I don't have a clue unless the electronics has a problem after the motor gets hot. Motor is in mint condition. Less than 300 hrs run time and has been stored in climate controlled shop when not in use and no water in gas tanks.<br /> My mechanic said it might be the VRO. Any ideas?

 

[R.Johnson]

Re: 150 johnson stalls

You have to start right at the basic's here, compression, ignition, fuel. You will need a manual, plus the proper tools. A VRO would certainly not be the fisrt thing yhat would pop into my head.

 

[MCM]

Re: 150 johnson stalls

How far off do the rpms drop? by half or just a little?

 

[Stinkbait]

Re: 150 johnson stalls

Hi R.Johnson,<br /><br />compression, ignition all check out good.<br />fuel tanks drained and cleaned, new oil mix.<br />The motor runs great at 5200 rpm for about 10-20 minutes, then the rpm drops off to 4000 or less, motor startes to shake/vibrate and has once came to a complete stop but remained idling. Once in the shop I trimmed the motor up to max and fuel ran out of all three carburetors.

 

[Stinkbait]

Re: 150 johnson stalls

MCM<br /><br />I have been running it at max rpm about 5200 for testing. It usualy drops down about 4000 rpm, once it came to a hault but continued to idle.<br /><br />I'm fishing for a fix before I turn it over to a mechanic, $75.00 an hour adds up quick. I'm a fair mechanic myself but this one's got stumped.

 

[MCM]

Re: 150 johnson stalls

Well some ign. parts can become temperature sensitive before failing completely. Does it only do this after warming up? does it run normally if given a chance to cool off?

 

[Stinkbait]

Re: 150 johnson stalls

After it has started doing what ever it is doing it never runs good again, well after I go through everthing again it run great. I 've only had three test runs and they all do the same thing, even after replacing parts and cleaning everything. It is 65 miles to the lake so trips are few and far between.

 

[MCM]

Re: 150 johnson stalls

Have you got a set of muffs for the motor so you can run it without going to the lake? also what kind of electrical test equipment do you have? have you got the service manual for the motor? sounds like you probably do.

 

[Stinkbait]

Re: 150 johnson stalls

I got a manual, Flute meter, motor muffs, compression gages.<br />I have never got the motor hot enough to start the problem. I'm not sure about running for a long time without the foot in the water.?????<br /><br />It will run good after cleaning the plugs using the muff but there again it don't get hot. This is why three trips to the lake...heat it up.<br /><br />I do thank all of you for your replies....looks more and more like I'm going to have to turn it over to the mechanic, you know the one that has that smile like a mule eating briers when you hand him the keys. <br /><br />I think I'm calling it a day and go home and work on my boat. By the way is there anybody out there that knows where they put all the bass at lake Oconnee, Georgia. If I ain't fishing I ain't happy. You guys have a great weekend, I'll check back Monday...............Michael Abbott in GA.

 

[MCM]

Re: 150 johnson stalls

This might be a long shot but its possible.<br /><br />Vapor Lock And Difficulty Restarting A Hot Engine<br /><br />"Vapor lock" is loss of power or engine shutdown due to gasoline vaporization in the fuel system. Vaporization prevents the fuel pump from delivering sufficient gasoline to the engine. Factors favoring vapor lock are high ambient temperatures which accompany high power output. Sometimes vaporization occurs after the engine has been intentionally stopped because of the cessation of mechanical cooling and fuel flow. In this case, the hot engine will be difficult to start.<br /><br />Vapor lock and hot restarting have been reoccurring problems for engine manufacturers. Some manufacturers are concerned that oxygenated gasoline will aggravate these problems because adding either ethanol or MTBE to gasoline increases volatility.<br /><br />The volatility of gasoline sold in each area of the country is tailored for the expected ambient temperature range. Buying smaller amounts of gasoline more frequently make it more likely you will have a gasoline of the correct volatility.<br /><br />Your owner's manual may suggest additional ways to avoid vapor lock. Remember that some situations lead to vapor lock more often than others. One is running an engine at full power for an extended time on an unseasonably warm day. If vapor lock does occur, it will probably be necessary to allow the engine to cool before it can be restarted

 

[Walker]

Re: 150 johnson stalls

Well, first thing I'd do is replace the water pump. Then I'd pull all the coils and clean their grounds and where they ground to the block. The reason I say replace the water pump is your motor should reach operating temp even on muffs. If ots getting hoooter while you run at throttle your water pump isprobably weak.

 

[MCM]

Re: 150 johnson stalls

Or t/stats could be stuck open as well.

 

[R.Johnson]

Re: 150 johnson stalls

Forget about vapor lock on a outboard motor! By the time an engine becomes that hot under the engine cowl, the engine is long gone.

 

[MCM]

Re: 150 johnson stalls

Well that was just something I ran across and copied and pasted from maxrules.com website. No personal experience with it except in an old Ford.

 

[Stinkbait]

Re: 150 johnson stalls

I'm back...long weekend. <br />I think I have isolated the problem, but not sure what's causing it. #1 plug is always covered with carbon after running and the motor rpm drops. Will swap coils around to see if that's it and get a new set of plug wires, they are old. The water pump was rebuild a few weeks ago, it was working fine just old.<br /><br />There is one device that I'm not sure what it is. It is located above the VRO and the fuel line from the VRO to the carbs has a "T" connecting it to this device. Guessing I would say a pressure guage or a fuel sensor. Has a couple of wires connected to it. Not shown are mentioned in my manual, at least I haven't found anything.<br />Any of you ever fished in GA.

 

[angus63]

Re: 150 johnson stalls

It may be a vacuum sensor for a fuel restriction. My 95 175HP has one.

 

[Stinkbait]

Re: 150 johnson stalls

It is on the pressure side of the VRO. If I remember correctly I have alarms that sound whem low fuel or no fuel and I don't have sensors in my tanks

 

[Walker]

Re: 150 johnson stalls

Check the recirculation valves, especially the one that goes to the cylinder that carbons up the plug.

 

[angus63]

Re: 150 johnson stalls

http://www.ishopmarine.com/ishop/jsp/AsplIsmCcatViewBase.jsp?reqFor=29&req4Browse=1&lvlCode=5&pCode=C0195285&path=BMC~A0000021~M0010086~M0010110~M0010112~C0195285&isForSupStore=fal se&cCatFilter=&eCatSupFldr=<br /><br />Check out the link above, sure sounds like the vacuum switch (item #10)you are describing. Only electrical device in the fuel system after the VRO. Like Walker said, a syringe with alcohol will clean up those recirc valves and really help the idle condition.<br />Good luck

 

[gatorred]

Re: 150 johnson stalls

gee plug oil line disconect wire and put oil in gas tank 50-1 is cheep fix if pump works no more oil injection it's in omc book more for doing that