1989 johnson 120 runs 2500rpm at full throttle

[buggyman20]

I have a johnson 120 1989 year. I put new kits in all the carbs. Fresh gas. I can squeeze the bulb till it gets hard. I see no leaks. When I took it to the lake it ran good for about 15 min. then it died. It started back up but will not get above 2500 rpm with the throttle all the way down. I got it on the trailer I checked the fuel filter it was full of gas and when I got home I took the plugs out of the float bowls and they were full of gas. While cleaning the carbs I shot cleaner in every hole in the carbs to clean them out. Any ideas?

 

[jonesg]

Re: 1989 johnson 120 runs 2500rpm at full throttle

It was probably overheating and you never noticed.
A temp guage is a handy thing to have next to the tach.
It went into SLOW mode, the powerpack limits rpm at 2500.
When you run it again it will be ok until it gets hot.
www.outboardbooks.com
How old is the water pump?
Thermostats?

 

[buggyman20]

Re: 1989 johnson 120 runs 2500rpm at full throttle

The impeller is less than 2 years old. What would be a good temp meter to buy? It has a strong stream of water coming out of the tube at the back of the motor. should the overheat buzzer go off? Thanks

 

[reeldutch]

Re: 1989 johnson 120 runs 2500rpm at full throttle

check the compression.

 

[noelm]

Re: 1989 johnson 120 runs 2500rpm at full throttle

before you start going crazy replacing bits and pieces, first off, we need to know was it OK before the carby rebuild? have you checked that you put everything together properly and you are indeed getting the throttle fully open? is the timer base correctly connected and adjusted, is the fuel vent open and clear? if you have a self inflicted fault, do not make it much worse by fooling around with stuff that may be perfectly OK.

 

[reeldutch]

Re: 1989 johnson 120 runs 2500rpm at full throttle

well he said it was running great for about 15 minutes that indicates that the trothle valves were open and everything was working fine.

he could have have an overheat and go in slow.
or he could have run the engine lean and blew a cylinder or 2.

i would defenatly check compression and go from there.

 

[buggyman20]

Re: 1989 johnson 120 runs 2500rpm at full throttle

I have not ran it much the last year or so but when I did it would be sluggish out of the hole. Once it got on plane it would run ok except for spitting and cutting out at top end. But it never died going wide open. After it died it started back up but it would not have enough power to get on plane. It sounded like it was bogging down. I took out one of the jets and it was clogged up. I thought I would clean the carbs out and it would run ok. Like I said I have no fuel leaks that I can find. It acts like a merc I used to have would when the o-ring at the fuel screen busted and leaked. Thanks

 

[reeldutch]

Re: 1989 johnson 120 runs 2500rpm at full throttle

oh boy do a compression test

 

[noelm]

Re: 1989 johnson 120 runs 2500rpm at full throttle

yep, by the sounds of this a compression test is in order, also note the condition of the plugs when you pull them out, if one (or more) is odd to the rest, take note of the compression in that cylinder especially.

 

[buggyman20]

Re: 1989 johnson 120 runs 2500rpm at full throttle

What should the compression be?

 

[SparkieBoat]

Re: 1989 johnson 120 runs 2500rpm at full throttle

hopefully over 100 psi but anything over 80 should run fine as long as all cylinders are with in %15 from lowest to the highest. %10 is way better.
after compression check, get a spark gap tester (less than $10 at auto parts store) check fire. (remove all plugs to check fire.) If compression is good and fire on all cylinders are good, then check all fuel lines and filters, next thing to check would be the fuel pump. My $$$ is on a bad fuel pump.

 

[buggyman20]

Re: 1989 johnson 120 runs 2500rpm at full throttle

I just did comp. check cyl 1 was 115, 2 was 118, 3 was 115, 4 was 125. I did run the engine about 5 minutes to warm up. I noticed the number 3 plug was not as wet as the other three. Like I said I went several years without using the boat a lot. Any more ideas? Thanks for all the input so far.

 

[reeldutch]

Re: 1989 johnson 120 runs 2500rpm at full throttle

so basicly what you are saying is that the carbs are clean and according to the compresion test internal parts are good.

i would run it on a plastic 6 gallon fuel tank with the vent open and run it wide open, checking the temp every few minutes while underway.
also before you go make sure the overheat alarm is working.


good luck

 

[buggyman20]

Re: 1989 johnson 120 runs 2500rpm at full throttle

I will try that. If I have a steady stream of water out the back would that be a sign the impeller is working ok? It idles great. What about the fuel pump in the VRO pump? No fuel leaks. If you can think of anything else please let me know. Thanks

 

[SparkieBoat]

Re: 1989 johnson 120 runs 2500rpm at full throttle

just because you are getting a stream out of the tell tell hole does not mean that the impeller is ok. You should replace your impeller every couple of years or so, some guys replace it yearly when they change the foot oil also. also have you tested the spark with a spark gap tester?? should be a hot blue streak at 1/2" gap. also I still think you got a fuel pump issue, have you tried pumping the fuel bulb while running to see if that helps, if its the fuel pump it should surge a little when you pump the bulb, also it could be a bad power pack stuck in SLOW mode if you get exactly 2500 rpms with no surging. so I think fuel pump or power pack

 

[buggyman20]

Re: 1989 johnson 120 runs 2500rpm at full throttle

I read another post about a thermostat being stuck closed. Can you tell me if there is a thermostat on a 1989 120 Johnson. if so where is it? I am getting a spark tester tomorrow. Thanks for the info about the gap, I did not know that. What about a coil that the plug wire goes to going out? Just checking out all the options. Thanks

 

[SparkieBoat]

Re: 1989 johnson 120 runs 2500rpm at full throttle

yes it has 2 thermostats, located above your top spark plug on each head. I think it has 4 small bolts holding the housing. here is a link to an exploited view..you really need a manual.
http://shop2.evinrude.com/ext/index.aspx?s1=a5f81aa6c104e4984e1e7b224f0d765e
be sure to get a new gasket for each, you could try removing the t-stats, and testing, but it is probably time for a change anyway, I cant remember if we talked about it but if it has been a couple of years change out the impeller also.
the gap tester will go where the spark plug should plug in at, this will test each coil. remove all plugs and test one wire at the time, be sure other plug wires are away from the block while testing to avoid arcing out.

 

[buggyman20]

Re: 1989 johnson 120 runs 2500rpm at full throttle

I had a good spark on all wires. How hot should the cylinders get when running at 3000 rpms for about 5 to 7 minutes? I put a digital thermometer on them and it read between 148 and 151 degrees. That seems a little hot to me for such a short time. The lower unit was in a tub with water from a hose being put in the tub. Toward the end of the time it did start to spit and cut out more. I squeezed the bulb but there was no change.

 

[reeldutch]

Re: 1989 johnson 120 runs 2500rpm at full throttle

you can really test it in a bucket.
you got to put it in gear and put a load on it to really test it.

148 to 151 is good.

temperature around 180 is overheating and could set off slow mode.

what you have to do is make it happen again in the water and check the temp.
use a 6 gallon tank.

a clogged vent could restrict fuel system cousing starvation at high speed and not at low speed.

 

[SparkieBoat]

Re: 1989 johnson 120 runs 2500rpm at full throttle

ditto that, I still think you may have a faulty power pack.