Need help on 1991 johnson 40 hp motor

[Boatgirl1984]

I am new to the forum and am hoping i can get some help to stop the money drain on this motor. I bought the boat used and had problems with the motor idling. I was told by a boat mechanic that was an authorized johnson dealer that i needed a new ignition module. After waiting for the backorder part i had it installed but then was told the carbs needed to be rebuilt. I had that done and took my boat to the lake where it stated right up, idled great, whet a little ways at 5 to 10 miles per hour and then opened it up to full throttle for about 10 minutes. I went into a cove and slowed to 5 miles an hour and then came back out and gave it full throttle only to have it kick into S.L.O.W. I used the trolling motor all the way back. When i was almost back i tried it one more time at full throtle and it went great. It is showing plenty of water, i replaced the heat sensor thinking it might be faulty. Took it out again today and the same thing happened. I replaced the primer bulb as it was not getting hard and the mechanic said it had a bad valve in it. I took it out again and the same thing happened. This time when it was in the S.L.O.W mode i reached back to the primer bulb and it was soft. Could there be an air leak somewhere that would cause the same issue or is that a vro issue. Please any ideas would b appreciated. The mechanic said to bring it back again and he would take it out on the Lake, but i can't even imagine what that might cost. Thanks

 

[jasper60103]

Re: Need help on 1991 johnson 40 hp motor

... The mechanic said to bring it back again and he would take it out on the Lake, but i can't even imagine what that might cost. Thanks

Boatgirl,
I wish he would have lake tested his work in the first place, and quit guessing for more things to charge you for. But I guess a tank test is what they normally do. Sorry, I'm just venting. Hopefully someone will chime in with some ideas.

 

[clanton]

Re: Need help on 1991 johnson 40 hp motor

Disconnect the temp sensor and do a test run. If ok replace waterpump, check thermostat. Not ok, check charge coil, which tech should have done, or replaced with new. Check all wires for the ignition system, very easy to pinch a wire when changing the ignition module. I would call BRP and inform them what kind of work there dealers do.

 

[Rick.]

Re: Need help on 1991 johnson 40 hp motor

Agree with above. Just to clarify things your bulb should only be hard when you first pump it. Once the motor starts running the bulb simply becomes a part of the suction hose and therefore will be soft, not collapsed, but soft. Best of luck. Rick.

 

[Boatgirl1984]

Re: Need help on 1991 johnson 40 hp motor

Thanks for the suggestions. I just replaced the temp sensor Friday. That didn't change anything today when I took it out on the lake. It still ran great for awhile then it when into the S.L.O.W. Mode where it won't allow me to go above 1500 rpms. How would the thermistat affect it? The water is going out strong, wouldn't that mean the water pump was okay? I keep trying to make sense of this. Thanks for the bulb clarification.

 

[Rick.]

Re: Need help on 1991 johnson 40 hp motor

Water flow from the tell tale is an indication your water pump is functioning. The water at the tell tale doesn't indicate the engine is cooling properly however. You can still overheat with a functioning water pump. The above comment about changing the stat. is a good one and a good place to start. If your engine is overheating you could eventually cause engine damage. Change the stat. or even temporarily try running it with no stat. just to see what happens. Once the engine is up to temperature you should be able to hold your hand on the head for a three count, that would indicate the motor is not overheating and the SLOW problem is caused by something else. Rick.

 

[Boatgirl1984]

Re: Need help on 1991 johnson 40 hp motor

Let me bring you up to date on what we have tried. After replacing the over temp. sensor and checking all of the engine wiring, we were on the lake again.* After a normal start and short distance (2 or 3 minutes) through the no wake zone, the throttle was increased to max.* The engine responded with full power and settled in at 4000 RPM and 30 MPH.* This is a 1991 17 ft. aluminum Bass Tracker PRO-17 with the original 40 hp Johnson Tracker engine).* After 2 or 3 minutes of WOT, we brought the throttle back to the neutral detent and the engine went to it?s normal idle speed of 1000 RPM.* The engine cover was removed and I placed my hand on the head.* It was barely warm???* After about 30 seconds to 1 minute at idle, the throttle was again advanced to max.* This time the engine exhibited the problem where RPM would only rise to about 2000 RPM and the engine ran rough.* We disconnected the tan wire going to the UFI ignition module believing that should remove any ground to the ignition module that might be coming from the over temp. sensor or VRO2 unit. and causing the RPM limit.* The engine still had the problem.* The over temp. sensor was then* disconnected as was the wires from the low level switch in the oil tank and the 4-wire connector for the VRO2 unit just to be extra sure the S.L.O.W. circuit was disabled and not causing the problem.* The problem was still there.* If my troubleshooting logic is correct, I?m beginning to believe we may have an intermittent loss of spark to one of the cylinders.* This possibility didn?t occur to me until we were half way home or we would have done some checking around the spark plugs and ignition coil.* Is it possible we could be dealing with a loss of spark problem to one of the cylinders?* BTW, I removed the thermostat and was able to blow freely through it so a new one is on order. One thing that is so strange is that every time I have gone to the lake to trouble shoot, the boat starts right up, it idles fines, goes thought the no wake zone and then goes great at full throttle and then idles down nicely and then when I try and go full throttle again it will not go above the 1000 pr so rpm's. If I put it in neutral and then give it gas it rev's right up. I realize the boat is not under a load at this point, but it seems that if it is having the S.L.O.W mode then it wouldn't matter. If the thermostat is stuck open it shouldn't cause it to overheat should it? Anyway I feel like I am back to square one. Any additional ideas would be appreciated. Thanks I don't know how I hit the smiley face, I certainly don't feel happy yet.

 

[Haffiman]

Re: Need help on 1991 johnson 40 hp motor

Take the UFI system and throw it faaaaar away!
Install, use old parts from a scrapped engine if possible, and install the normal external power pack!!
That said, your max rpm seems a bit low.

 

[Boatgirl1984]

Re: Need help on 1991 johnson 40 hp motor

I assume that UFI has to do with the VRO2 system. I am a little confused when you said use used parts, are you referring to the power pack, VRO2, or what? Thanks.

 

[Haffiman]

Re: Need help on 1991 johnson 40 hp motor

UFI or 'under flywheel Ignition' module was a disastrous system. In old language, Powerpack.
This is the part activating the SLOW function when activated by No Oil(VRO) and High Temp. If you get SLOW and no alarm - this unit is acting up. As it has recently been replaced, claim warranty!!
BPR came to their senses and scrapped the system and reverted back to the old external power pack. A rebuild' almost cost less than a new UFI module and lasts! Should the pack go, it is a fraction of the price of the UFI module.

 

[crestlinermusky]

Re: Need help on 1991 johnson 40 hp motor

I am guessiing that thhe VRO oil system is all intact, Get rid of it and install a normal fuel pump where
you have to premix the gas. It sounds like the oil pump is cutting out under a load and the motor is going into safe mode.
It is common for this system to go on this motor. I had the exact same motor and the same problem that was solved by removing the
VRO system. When I bought the motor in 1991 I was told by my dealer that the system would fail eventually. Two years later it did, and
I removed it and put a normal fuel pump and the motor ran like a dream untill I sold the boat in 2005.

 

[Boatgirl1984]

Re: Need help on 1991 johnson 40 hp motor

Thanks for all the good ideas. I have an appointment with the guys who originally put in the new ignition module. They are going to take it out on a lake and check it out and see if the new one is faulty. I made sure I would not be charged for their boat ride. I live about 1 hour away from the nearest marine mechanic so getting the boat to and home again multiple times is a pain in the ***. I wish I was able to do more of my own work but I just don't have the mechanical know how. I really appreciate all the info as it has helped me understand the workings of this motor. My appointment is on Friday. I will post what I find out and go from there. Thanks again.

 

[Boatgirl1984]

Re: Need help on 1991 johnson 40 hp motor

Wanted to thank everyone for the help. I had the ignition coil replaced and the thermostat and now it is all good. Took it out on the lake and it ran great. Thanks again.

 

[Boatgirl1984]

Re: Need help on 1991 johnson 40 hp motor

Well Iam back again. When I took the boat out on the bigger lake the boat went into the slow mode again. I guess I didn't run it long enough for it to kick in the last time i took it out after the new iginition coil and thermastat. I took it back down to the boat guys and they took it back out and finally got it to do it when they had it out. Turns out the motor was dropping a cylinder. The replaced ignition module was faulty. I had heard when I was waiting for the first one to come in that Johnson had a back order of 365 of those modules. I had found one in a place back east but when that one was installed it too was faulty. I then waited till they received another module and that one was also no good. When the mechanic asked the distributor they told him they hadn't had any back orders on that part and that they had plenty in stock. The mechanic told hem to go ahead and send out another module. The mechanic asked me if I ever had a problem with turning the motor off, as when they were checking out the so called bad module it wouldn't turn off the motor when the key was turned off. Now I have to wait till the new module shows up and it gets installed. At least it finally acted up with them out on the lake. hopefully Johnson got rid of all the faulty ignition modules. Anyone else have a motor that didn't turn off when the key was turned off? Thanks

 

[Haffiman]

Re: Need help on 1991 johnson 40 hp motor

The UFI modules are unfortunately 'faulty' by design. Ask your 'guys' to do what I suggested earlier, throw away the UFI and install the 'old' system!!

 

[Boatgirl1984]

Re: Need help on 1991 johnson 40 hp motor

I looked back and read your earlier post. When did they scrap the under flywheel module? Where should I look to find the one you are talking about? Are there any newer ones that are aftermarket? You mentioned a rebuild. I assume you are referring to finding an old one off a Johnson motor that had the other kind of module. Sorry, I know I sound a bit confused.