1991 40hp Johnson

[cpinkert]

Hi everyone,

I've used this site a couple times to find answers, but I can't figure out the issue I'm having with my motor.

Basically, last fall I was going full throttle and the engine bogged down (not sure if that is the proper terminology, but it basically just cuts out without dying). I thought I hit a log. I tried getting back up to full throttle, but the engine wouldn't go over a certain RPM without cutting out (boat normally goes 25mph, would only go 6mph before reaching cut out point).

I replaced the fuel filter first, fuel line bulb next, spark plugs after that, and then bypassed the VRO pump and installed a fuel pump and mixed the gas in the tank after the first three things didn't fix the problem. None of these things fixed the problem, and the last time I had the boat out last fall it wouldn't keep running unless I kept on choking it. I read on here that having to continuously choke the engine is a sign that the carbs are clogged, so I brought it to a mechanic this spring and he cleaned and adjusted the carbs. It ran great the first time I had it out. However, I've now had it back into the mechanic 3 times because the problem continues to come up. Every time, the engine works great for a while before the problem shows up again. Sometimes the problem only happens once in a day. Those times, I'm typically almost to where I'm going, fish for a while, then start it up and it's fine and runs great. Other times, the problem is an all day thing and I end up going 6mph back to the access.

Any ideas of what might be going on and what I could try next? Somebody I was talking to said it sounded like the fuel lines might be collapsing. Seem reasonable? Should I just try replacing the lines? Is it possible that something is clogging up the fuel line opening in the gas tank?

I'm confused and frustrated, any help would be appreciated.

Thanks in advance,

Chris

 

[tashasdaddy]

Re: 1991 40hp Johnson

welcome to iboats. ok, we need to do some trouble shooting, instead of throwing parts at it. have you check your spark when the motor is acting up? have you checked to see if the fuel line bulb is collasping (going flat). are you sure the vent on the fuel tank is open, or if built in tank, not clogged? also if running a built in tank, do you have a fuel/water separator?

i'm leaning toward a spark problem. coil or power pack getting warm and failing.

i have a 93 40, same motor. you are our eyes and ears, the more complete you answer the questions, the better the advice.

 

[cpinkert]

Re: 1991 40hp Johnson

I haven't checked the spark when the motor is acting up. How do I check that? Pull the plug, leave it attached to the plug wire, turn the key and check for spark?

The bulb is not collapsing.

I am not sure the vent on the tank is open, haven't checked it, but I'm assuming it is because I've owned this boat for a couple years and used it a lot before the problem arose. I did try running the motor with the gas cap off, didn't help. Not sure if that does the same thing as a vent on the tank? I'll pull up the floorboard and check the vent tonight to see if it is clogged.

I'm not sure if I have a fuel/water separator. Is that something that comes standard on some motors or is it an add on. I have the repair manual and the owners manual for this motor so I can probably check on that.

 

[tashasdaddy]

Re: 1991 40hp Johnson

fuel water separator, looks like an oil filter, usually mount on the transon, or in the splashwell. built in tanks are noted to collect water. take the boat out run close to the launch, get it to act up. now with it running, and insulated pliers, remove a spark plug wire. you should notice a change in the way the motor runs, replace wire, and do the other one. that motor will run on only one cylinder.

if you get no change on one. and the engine dies, when the wire is removed, the coils that did not have any change, is 99% the culprit, and needs to be replaced.

after you get it running, get a separator.

 

[cpinkert]

Re: 1991 40hp Johnson

Took the boat out last night, got it to act up, and removed the plug wires one at a time. Neither caused the motor to die. Anything else I could try?

 

[dimock44]

Re: 1991 40hp Johnson

Chris
My boat acted pretty much the same. I found Crap in the gas tank that looked like black dirt. I strained the gas through a paint strainer and the black stuff was rubber from the inside of the filler tube. Stick your finger down the tube and rub the inside of the rubber hose. Guess it would collect on the pickup strainer and then release later. Cleaned the tank and replaced the filler tube (napa). If you can remove the tank or see into it its worth a check. Good luck and let us know

 

[cpinkert]

Re: 1991 40hp Johnson

Well, I hooked up a different gas tank and took it out last Friday, same results. I do have a question regarding the coil tests. You said to test the motor while it was having the problem. When I tested it, I took the boat out, the engine did the same thing, I put it in neutral and pulled the wires off one at a time. However, the motor wasn't having the problem when I tested it because it was at lower RPM's. Should I leave the motor going at high RPM's so that it is cutting out when I test it? I'm assuming yes, but how do you do that? Sometimes after the motor has the problem I put it in neutral and it is fine at higher RPM's. If I leave it in gear, I run the risk of getting thrown off the boat! lol.

Anyway, I'm still not sure what to do. If there was a problem in the coils, would it likely be the ignition coil? I'm looking at the SELOC manual I have for my motor and it mentions a charge coil and power coil. The ignition coil I found for my boat looks like it would be an easy fix and relatively cheap if that didn't turn out to be the problem. ~$25

Any ideas?

Thanks,

Chris

 

[cpinkert]

Re: 1991 40hp Johnson

bump

 

[cpinkert]

Re: 1991 40hp Johnson

Well, I broke down and took the boat in to a mechanic. He said the high speed went out in the stator and something else under the flywheel and put in a conversion kit. The motor runs great now, but it seems to have developed a new issue and I'm wondering if the mechanic messed something up. Basically, the motor doesn't shift into reverse. When I was taking the boat off the trailer last night it didn't shift into reverse right away. Rather, it revved up a bit and then it dropped into reverse. Didn't sound good at all. I tried it again after I parked the truck, same deal. I've never had a single issue related to shifting with this motor before this, so I have a hard time believing it just developed while it was at the mechanics for a month.

I'm wondering if doing the work I mentioned above requires anything related to the gears to be removed from the motor or adjusted. When I called the mechanic this morning to let him know what was going on he immediately became defensive and said we only worked on the electrical, we didn't do anything with the gears. I have a hard time believing this guy because when I was picking up the boat yesterday his daughter (who worked on my motor) said she got it up to 3000rpm on the trailer and they didn't water test it, but the owner of the shop was trying to tell me they brought it out to the lake and ran it. Maybe they were saying the same thing and just left it on the trailer at the lake, but if they have water muffs why would they do that?

I'm not sure I want to bring it back to this mechanic. What do you all think?

Thanks in advance,

Chris