1990 johnson 150

[whisker]

hi guys,
i was giving a johnson 1990 150. it runs but low compression on one cylinder. i was thinking of tearing it down and rebuilding it. i have rebuilt engines before but not outboard. are these engines hard for a newbie to rebuild. also what special tools if any would i need.

 

[tashasdaddy]

Re: 1990 johnson 150

i would mount it on a very substantial stand, or transom and do a decarb. this may clean up what is causing it. if decarb does not clear it up pull the head, possible blown head gasket, it will have to come off anyway. $20 head gasket may cure it. unless, you find otherwise, they should last for 40 years with out a rebuild.

i like this method.
Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck

 

[baiwan]

Re: 1990 johnson 150

It's a piece of cake. Just have to make sure not to break bolts.
I enjoy rebuilding my 90 hp now without a manual and difficulties in getting spares. Broke only 3 bolts so far and expect to have another two.

 

[JB]

Re: 1990 johnson 150

Please be more specific about your compression.

Too often people get paranoid about compression and jump in to fix stuff that ain't broke.

 

[whisker]

Re: 1990 johnson 150

hi jb,
all the numbers are a little low in my opinion. left bank 81-85-75.. right bank 90 91 91..what u think

 

[JB]

Re: 1990 johnson 150

I don't think it needs a rebuild. I think it needs a decarb and another compression test.

Those big V6s often show an average compression around 85-90psi when still sound.

 

[whisker]

Re: 1990 johnson 150

so you are saying thats close to normal. im use to the mercs. my last merc has compression over 135 in all 4 cylinders. what is factory specs on that big boy when it was new.

 

[whisker]

Re: 1990 johnson 150

also i was told it was hard to start but did run. was told carbs had already been cleaned,new plugs,etc..

 

[tashasdaddy]

Re: 1990 johnson 150

unless they were properly cleaned, they are worth looking at. human error also makes them hard to start. not using the proper starting procedure, or the primer solenoid not working.

http://forums.iboats.com/showthread.php?t=225510

 

[JB]

Re: 1990 johnson 150

There is no spec on psi, Whisker. Guages, conditions and technique vary too much,

 

[Dhadley]

Re: 1990 johnson 150

It also depends on what model 150 it is and which heads & head gaskets are on the motor. I wouldn't worry about it too much. A good decarb and see how it runs.

 

[jonesg]

Re: 1990 johnson 150

Your model number might indicate it to be a commercial variant, they are designed to run lower compression.

ahh but you didn't post the model number eh? hehehe

those numbers aren't far off mine which starts ez, idles very well and has good power. I bet those numbers will come up with a seafoam treatment.

 

[whisker]

Re: 1990 johnson 150

thanks for all the help,

if i think this motor is good it will replace my merc 115 2+2 carbs. will there be a performance increase? enough to justify the trouble anyway..also i need new wring harness for johnson anyone know where i can get good deal on those. thanks

 

[jonesg]

Re: 1990 johnson 150

Try craigslist....or ebay for cheap controls.
You can find the service manual on ebay too. I got mine for $40.


I don't know how they all compare but any decent 150 is going to beat a 115.
My reason for buying Johnson was due to the level of expert help available here.

 

[JB]

Re: 1990 johnson 150

The 150 will offer a significant increase in performance, Whisker.

 

[splitshot]

Re: 1990 johnson 150

Definately get a manual they are very very handy..do the decarb, if no improvement pull the heads if pistons are chewed up then you can tear it down if not then you can put the heads back on and run it !!

 

[whisker]

Re: 1990 johnson 150

i got model number on my outboard.. it is j150 txesb..does anyone have any info on this.

 

[cdnfthree2]

Re: 1990 johnson 150

Since they're all so close I think they've all gunked up over time together. once u decarb u will not know what hit u. If it improves, repeat the decarb process. Motor is probably great. My 150 is a major power house for my 19footer and a gas hog too, but your going to love it anyways. After two consequtive decarbs, I had alot of cleaning to do below my exhaust but man did it do alot for the performance.

 

[splitshot]

Re: 1990 johnson 150

J=Johnson 150=150 horsepower X= 25"shaft es= 1990 (year it was built) dont know about the "t" and the "b" others should be along to help

 

[whisker]

Re: 1990 johnson 150

is this a looper engine?