Johnson 120/140

[lakerunner]

I was wondering what would be required to upgrade a 1990 120 Johnson to 140 hp. The specifications in the manual (bore,spoke,pistons,) are the same so where does the extra 20 hp come from (Carbs,jetting,porting)?<br /><br />Lost compassion on #2 and looking at rebuild anyway just as well pick up a few more ponies on the way if possible.

 

[Dhadley]

Re: Johnson 120/140

The difference is in the reeds. Install Boyesens and you'll have it. Dont expect to see any difference unless you have a boat that responds very well to small torque increases. If you are set up to turn less than 6000 rpm, dont expect to see any difference.<br /><br />Good luck!

 

[93bronco]

Re: Johnson 120/140

nice motor easy to work on, if you dont have a parts and omc repair manual i would get one. ebay has them all the time. i think the next time i need a rebuild im going to try this site. they have one vendor(#4) that will give a up to a 24mon no fault warranty. at $2124.00 not including core charge is pretty fair w/ 12mon no fault. good luck

 

[ob]

Re: Johnson 120/140

lakerunner , The carburetors on the 120 hp verses the 140 hp are identical with the exception of the intermediate orifice size.The 120 takes a #50 and the 140 uses a #54.You can refer to this drawing for location.Intermediate orifice is #19.<br /> 120/140 carb

 

[93bronco]

Re: Johnson 120/140

after looking back in parts manual the reed box assemblies are different along with the intermediate orifice as stated above.<br />but it also shows that the intakes are different as well as the manifold screws from 120 to 140.

 

[dpminc]

Re: Johnson 120/140

Had some spare time, and looked it up. The manifold is also different.

 

[Terry H]

Re: Johnson 120/140

The only other item I find different is the exhaust tuning megaphone...Dhadley is right on with the reeds on this one...you can gain alot of power by changing to the Boyesen reeds, and having a good link & sinc on this motor...just a Thought

 

[lakerunner]

Re: Johnson 120/140

Thanks for all the info.<br /><br />I have the omc service manual but not the parts manual.<br /><br />Someone had told me the reeds were different (5 for the 120 and 6 with some type of coating for the 140).Looks like I'll need to scout around for a 140 or at less the induction system off of one.<br /><br />I'm going to attempt as much of this overhaul as possible myself. Really just like to see what makes things tick and why.<br /><br />Ya D the engine was turning a little over 5500 when it dropped the cylinder. Not sure if it went lean or what. The other cylinders look perfect. Had 130 psi of compassion on all the cylinders before. I had checked them that morning. Fresh gas, oil, and new plugs. Just singing along and bam.

 

[Hooty]

Re: Johnson 120/140

I'd sure find out what caused the one cylinder ta puke so it doesn't happen again.<br /><br />c/6<br /><br />Hooty

 

[rickdb1boat]

Re: Johnson 120/140

According to this site, the same reed box is used in both the 120 and 140.<br /><br /> web page

 

[HotRude]

Re: Johnson 120/140

Lakerunner I might be abel to help you. I just rebuilt one and changed it from a 120 to a 140. And did some cheap hi performance modifications. If you would like to e-mail me at, Janieron@cs.com . I can get you all the info. and specs. you'll need.

 

[lakerunner]

Re: Johnson 120/140

Hooty that is one of the reasons I'm taking my time breaking it down. So far the intake system and all the electronics or off. All four bowls were full of fuel. The electronics look ok but I haven't test any of it yet. Did find one thing wierd. There are four bolts that go though the intake into the intake runner just behind the reed cages three had 1/8 inch gobbs of silicon hanging in the passage. On the blown cyl it was missing. I wonder what a chunk of silicon would do when compressed and ignited?<br /><br />Rick thanks for the link. I checked it out and it gives two different numbers for the reed box and intake manifold. The number cast into mine is 328627. I'm not sure what that number relates to.<br /><br />HotRude you have mail.

 

[mattfl_34]

Re: Johnson 120/140

I have a 1989 Looper 140 that NEEDS to be re built that I can let you have for a price if you need parts.. <br />Im in Florida its in Central Florida<br />mattfl_34@msn.com<br /><br />I replaced it with a 2000 Johnson 150 and love it.

 

[HotRude]

Re: Johnson 120/140

Hey Matt_fl34 how much for the 1989 140 h.p.

 

[lakerunner]

Re: Johnson 120/140

HotRude what type of boat are you running? <br />Are you still running the VRO?<br />I still have it connected. Don't think it had anything to with dropping the cyl but I'm going to disconnect it now.<br /><br />I'm running a 1990 18' Hydra-sports.<br /><br />Looking to add a 6" jack plate when the rebuild is complete.

 

[HotRude]

Re: Johnson 120/140

I have a 1991 Skeeter Fish & Ski, 17', 6" jackplate. I have my VRO unhooked (my personal preference). How fast did your boat run before motor messed up?

 

[lakerunner]

Re: Johnson 120/140

With a very lite load maybe 50. The speedo doesn't work very well lol and never had it on gps or radar. Running a 13 3/4 x 20 Raker. All trimmed out the engine was turning 5600. The boat doesn't have a true pad.

 

[lakerunner]

Re: Johnson 120/140

Matthew you should have mail.<br /><br />HotRude We're heading up to St Louis Friday.<br />How's the weather up there?<br /><br />P.S. Did you replace the exhaust tuner also?

 

[HotRude]

Re: Johnson 120/140

Lakerunner, we had about 2" of snow Sunday night and its very cold here. No, the engine tuner and tuneing megaphone are the same.