1986 johnson 90 hp engine problems

[mike8282]

hey guys i have 86 johnson 90 hp, ive replaced all spark plugs, put in a new fuel pump, filter and fuel lines, cleaned the carbs and replaced all gaskets, using good fuel and right fuel ratio. but the motor is hard to start and runs rough at idle. theres no corrosion on any of the wires. but when i checked to see if the plugs were getting spark i noticed that the top two plugs were dry and black and the bottom two plugs were wet and black. i havent done a compression test yet but i wanted to know what the problem might be?

thanks

 

[emdsapmgr]

Re: 1986 johnson 90 hp engine problems

You may not have spark on the bottom two plugs. Put an inductive timing light on the plug wires. All 4 should show the same flashes from the gun. You will be able to see weak spark, no spark or intermittent spark through those flashes. Check your compression to make sure it is good before you put any repair $ into it.

 

[mike8282]

Re: 1986 johnson 90 hp engine problems

I had great spark on each plug. I also did a crompression test 1# 90 2# 120 3# 110 4# 110. The number 1 cylinder looks like it's running dry and lean. Would this be a carb problem?

 

[emdsapmgr]

Re: 1986 johnson 90 hp engine problems

Absolutely. If the engine was not put up for storage properly, the leftover fuel may have dried up in some of the carb passages. When this happens, the dried fuel can restrict fuel passages, causing running issues. Get two carb overhaul kits and a can of aerosol carb cleaner. You will want to blow out all the passageways of the carb bodies, comparing the aerosol flow rate from one passageway on one carb to the same passageway on the other.

 

[spingley]

Re: 1986 johnson 90 hp engine problems

I had the same problem as you and after replacing just about everything, including rebuilding the carbs I noticed that the throttle plates on the top carb were open a lot more than the bottom carb, after doing a somewhat link/sync it ran and idled great.

 

[Chinewalker]

Re: 1986 johnson 90 hp engine problems

Also - you say you replaced the fuel pump. That motor originally had a VRO pump, which incorporated the fuel pump. Has your motor been converted to standard fuel pump and mixed fuel?

 

[mike8282]

Re: 1986 johnson 90 hp engine problems

I noticed that my bottom plate was a little more open than the top and I adjusted them but still had some trouble getting the motor. But as soon as it startEd it would idle fine. But as soon as I shut it off it wouldn't start right back up it took a couple cranks. I think there might be some rsitance in the fuel line going to the top carb cause it seems like the bottom carb is recieving more fuel than the top. I've also cleaned the carbs but I'm thinking about taking them off again thoroughly cleaning out all the passage ways. And what's the best way to lube the lower unit? Yea i put in a new non vro pump and I'm pre mixing with a ratio of 50:1

 

[Chinewalker]

Re: 1986 johnson 90 hp engine problems

#1 cylinder compression seems a little off. I like to see no more than 5% variance between cylinders and you've got about 30% between lowest and highest.... Might be worth rechecking, as that could certainly cause rough idle.

 

[mike8282]

Re: 1986 johnson 90 hp engine problems

I retested the compression and the first cylinder is still about 95 but at top end all four cylinders are around 110-115. Also what's the best way to decarbonize without having to pull apart the motor?

 

[kenmyfam]

Re: 1986 johnson 90 hp engine problems

Also what's the best way to decarbonize without having to pull apart the motor?

Seafoam. See the "Top Secret Files" at the top of page one of this section.

 

[mike8282]

Re: 1986 johnson 90 hp engine problems

Now that I solved the starting and idling problems my outboard won't go after pushing the throttle full forward, It doesn't bog down. It just seems like the motor doesn't want to go. And it doesn't make sense. I put new fuel, spark plugs, all new fuel lines, cleaned the carbs, choke solenoid works, spark plugs have good spark. It starts up fine but it starts idle rough after awhile. I added seafoam to fuel at the right mix ratio, I don't know if this could be the cause of the motor running sluggish at top end or what. It does seem to smoke alot more now that I added seafoam to fuel but I just figured that was from carbon built up in the motor.

 

[emdsapmgr]

Re: 1986 johnson 90 hp engine problems

Have someone constantly prime the fuel hose bulb and see if it will run high speed.

 

[kenmyfam]

Re: 1986 johnson 90 hp engine problems

Yea i put in a new non vro pump and I'm pre mixing with a ratio of 50:1

O.K. So what pump did you put in ???

 

[mike8282]

Re: 1986 johnson 90 hp engine problems

I'll give that a try and I'll let u know if it works or not. I'm kinda thinking it could be that the pin that holds the float and the needle together could be adjusted wrong and it's not allowing enough fuel in to the carbs but I'm not sure. I bought the non vro from pro marine, the part number 8402-1

 

[kenmyfam]

Re: 1986 johnson 90 hp engine problems

I'll give that a try and I'll let u know if it works or not. I'm kinda thinking it could be that the pin that holds the float and the needle together could be adjusted wrong and it's not allowing enough fuel in to the carbs but I'm not sure. I bought the non vro from pro marine, the part number 8402-1

How about a photo of the pump ???

 

[mike8282]

Re: 1986 johnson 90 hp engine problems

i couldnt get a photo to upload but heres an up date, i put new spark plugs in and now the motor idles perfect shifts perfect with muffs on but when i take out to the lake it seems like back pressure from lake water makes the engine idle sluggish and wont reach full throttle. do you think it could be a timing issue?

 

[millsroofing]

Re: 1986 johnson 90 hp engine problems

hi not sure how to start new thread.so .......
i just bought a 2000 javelin venom f/s 17 with a johnson 115 and it doesnt have any batterys.what kind of batterys do i need for it? ,it has a 44 thrust trolling motor.

 

[mike8282]

Re: 1986 johnson 90 hp engine problems

optima marine batteries are good but pricy. but any deep cycle marine will work