90HP Johnson Running Rough *Pics & Video*

[Haffiman]

Re: 90HP Johnson Running Rough *Pics & Video*

Before tearing anything down and throwing money, do some more 'testing'.
!: Decarb the engine by using (BRP) Engine Tuner or Sea Foam.
2: Take the engine for a spin with front carb cover off and study the carbs throats. Are all main jets kicking in and giving equal amount of fuel?
PS: Running in the yard on muffs is mostly a waste of time when it comes to performance problems. Get the boat in water. Muffs are for flushing salt etc out of the engine only!

 

[Stryker23]

Re: 90HP Johnson Running Rough *Pics & Video*

well idk if it gotten louder, just has a different sound to it. The motor kind of shimmy's when under load. I'm going to order 4 new coils off here. Then rebuild the carbs. So i need a rebuild kit or can i just disassemble and clean and reassemble? Its like when i give it full throttle it only revs to about 2500-3000 rpm and wont go any further. here is a video of it idling, how does it sound to you guys? Is it normal for water to be spraying out of the two top exhaust ports like it is? Let me know what you think!

http://s33.photobucket.com/albums/d75/atvkid4eva/?action=view&current=90hpJohnson.mp4

 

[Haffiman]

Re: 90HP Johnson Running Rough *Pics & Video*

Looks like a dead cylinder. Water will come out of the two holes only when thermostat opens.
Add to my comment above:
Check engine temp and temp balance between cylinders. Engine temp at idle around 145F.

 

[glengold]

Re: 90HP Johnson Running Rough *Pics & Video*

yes, water should spray out those ports when the thermos open up. You shouldn't rev over 2000 in neutral, that is hard on the motor. Their designed to rev that high UNDER LOAD. Like stated before, new wires, coils should solve your spark issue. Decarb if you have never done it before, I recently gained 600 RPM after a decarb on an old 55 hp. Go through the carbs, one trick is if the gasket is black they have never been rebuilt. If the gasket is brown then they have and the gasket should be reusable, depending on how old it is. Be sure to clean out the jets and check the needle and seat. You may have a stuck needle, not allowing fuel into that carb. Good luck, take your time and do it right.

 

[Stryker23]

Re: 90HP Johnson Running Rough *Pics & Video*

it seems like water comes out of those ports as soon as i start the motor, is that normal? shouldn't the thermostats stay closed until they reach the required temp to open? And when you say it seems like a dead cylinder are you saying that the coils could still be my problem?

 

[Haffiman]

Re: 90HP Johnson Running Rough *Pics & Video*

Check engine temp, but if water is coming out immediately after you start the engine your thermostat(s) are most likely stuck open or missing??
If the coil is the problem, or something else, difficult to say, but do following test:
Pull out the plugs and bundle them together and ground, or even better, hook up a 4-lead spark tester.
Crank the engine and monitor that the plugs sparks in sequence 1-2-3-4 and only like that. You may even take side by side with 2 plugs at the time.
If 2 plugs sparks at the same time (1 -1,3 -1 -1,3), your powerpack at that side is most likely 'gone'.

 

[Stryker23]

Re: 90HP Johnson Running Rough *Pics & Video*

I dont remember water coming from those exhaust ports when the motor was running good when i first bought it.

 

[RandyJ]

Re: 90HP Johnson Running Rough *Pics & Video*

Kinda makes me wonder if the exhaust isn't stopped up. I had an old mercury 50 hp that I got a deal on because the owner (a well known shade tree outboard mechanic) couldn't figure out what was wrong with it. When I tore it down for parts I found the gasket between the lower unit and leg had gotten out of whack and was blocking the exhaust. With a blocked exhaust an engine will crank good and do fine until you open the throttle to rev it up... it will start to sound "different" and be sluggish and won't rev very high.

 

[Stryker23]

Re: 90HP Johnson Running Rough *Pics & Video*

but wouldnt a blocked exhaust make it run bad on the muffs as well? I think if it was blocked it would be a problem in or out of the water?

 

[RandyJ]

Re: 90HP Johnson Running Rough *Pics & Video*

The one I had ran fine at low RPM. Partial blockage will allow the exhaust to get out easily until it exceeds the capacity of the exhaust circuit. At low rpm's you'll hardly know the difference. I got familiar with this when old chevy's that had lined exhaust systems would run through water with their exhaust hot. The outer pipe would contract which would cause the inner pipe to collapse and partially block the exhaust. The car would crank and run fine but had no power and wouldn't rev up. If my poor memory serves me correctly... the spark plugs would get nasty too....

 

[Stryker23]

Re: 90HP Johnson Running Rough *Pics & Video*

how would i go about checking this? im not to familiar with these outboards

 

[Haffiman]

Re: 90HP Johnson Running Rough *Pics & Video*

Forget it, not relevant on this engine.

 

[Stryker23]

Re: 90HP Johnson Running Rough *Pics & Video*

Alright.also can you describe the decarb process? and do i wanna do this before or after i clean the carbs? So you guys would recommend just cleaning them or should i order the rebuild kit when i order my coils today?

 

[Haffiman]

Re: 90HP Johnson Running Rough *Pics & Video*

May I suggest you do the recommended tests on your ignition system and temp control before starting to order parts. Might save you quite some money knowing WHY you do what you intend to do. I do not believe that the carbs are the main problem until you may verify that they are not 'working'. The look on your video indicates one 'dead' cylinder and so do the max rpm. Is it a dead coil, a defect power pack or a spark jumping to the lower cowling latch??
However if you feel like pulling the carbs, please do.
Decarb: Run the engine really warm on idle. Remove the front cover of the carbs. Start the engine and spray a complete can of BRP engine tuner into the carbs. Keep the engine alive with manually operate the throttle plates. Leave the engine for an hour or more, start, in gear, about 1.3 throttle until engine clears up -then full throttle for 10 minutes to burn clean. However if you still have a dead cylinder - you might burn down a piston or more.
Get the engine run on all cylinders first!!!!!

 

[Stryker23]

Re: 90HP Johnson Running Rough *Pics & Video*

okay i will do some more testing. I am gonna replace the coils tho because regardless they need it. One other thing i noticed was that when i pulled the new plugs out to do my compression tests one of the plugs was completely dry and the others were a bit wet. Does this say anything? Id have to pull them again to verify.

 

[Stryker23]

Re: 90HP Johnson Running Rough *Pics & Video*

should i buy the sierra coils or spend a few bucks more and get the OEM ones? Any recommendations?

 

[Stryker23]

Re: 90HP Johnson Running Rough *Pics & Video*

well the OEM ones are a bunch more, so im just gonna get (4) sierra coils.

 

[Sprky]

Re: 90HP Johnson Running Rough *Pics & Video*

I posted how to figure out your problem. It gets even simpler when you are on the water.

 

[Stryker23]

Re: 90HP Johnson Running Rough *Pics & Video*

Sprky- I tried to do what you said, but when i went back to read your instruction it was only (...........). repost it and i will give it a try this weekend

 

[Sprky]

Re: 90HP Johnson Running Rough *Pics & Video*

Call and I wil walk you thru it. Too many variables.

Chris 512-264-3124