87 Johnson 40HP VRO starting/running question

[strosk]

Hey guys, my Johnson isn't starting/running properly. Let me give you the run down...

Went on vacation 3 weeks ago. The motor ran great, every day, for a week. Come home and put the boat in the garage and didn't touch it for 2 weeks. This past Thursday, charged the trolling motor battery for a fishing trip this past weekend. When I got to the lake and was preparing to launch, my tilt/trip didn't work. I quickly figured out that the key was left on and my cranking battery was dead. OK, so I swap the cranking battery with my trolling motor battery and I launch the boat. At the dock I use my normal starting procedure, but after 4 or 5 minutes I figure out that the motor isn't "warming up" like usual. It will not stay running if I put the warming warm up lever down, and also will not run unless I continually press the fuel primer. I checked the fuel connections, primer ball and vent. All seems normal. I'm sure you guys don't need the story leading up to the problem, but wanted you to have the whole "picture" from the time it ran great to the time it didn't. Thanks for any help you can give me while I continue to research...

 

[jtexas]

Re: 87 Johnson 40HP VRO starting/running question

...At the dock I use my normal starting procedure, but after 4 or 5 minutes I figure out that the motor isn't "warming up" like usual. It will not stay running if I put the warming warm up lever down, and also will not run unless I continually press the fuel primer...

using the primer to flood a warm engine should kill it immediately; if it doesn't, it's because gas isn't getting from the carb into the cylinder. sounds like you've got a blockage in one of your idle jets.

click on the "top secret file" at the top of this forum, follow the link to "carb cleaning and rebuild" for instructions on fabricating a jet removal tool. Don't try an ordinary screwdriver, it's too easy to mar the soft metal, which would screw them up.

 

[strosk]

Re: 87 Johnson 40HP VRO starting/running question

Jtexas, you're right. After a few minutes of running, the engine would stall, even using the primer. Up until that point, I had to use the primer to keep it going. It's pretty picky about starting procedure, and usually takes a couple minutes for the motor to warm up, so I wasn't that worried until 3 or 4 minutes in. I will start looking in the direction of carb cleaning. Just to clear my mind, is there anything that could have happend by leaving the key on?

 

[jtexas]

Re: 87 Johnson 40HP VRO starting/running question

The only connection the keyswitch makes in the "on" position is to connect the battery with switched accessories (just the stuff that only gets 12V when the key is "on"). Unless you have a radio or something on that circuit, battery must have drained through the tachometer and whatever other gauges you have.

 

[Scottycat]

Re: 87 Johnson 40HP VRO starting/running question

It's either your low speed circuit, your plugs, your compression or your gas is bad.

The low speed is the one on top of the carb on the face. You may have to file down a small flat head screw driver to get it out.
No idle?

Drop that carb and clean it good, in acid.
Replace the gaskets, fuel needle and seat.
No idle?

Drain your tank. Re-fuel with high test and new oil.
No idle?

Check that compression. ( I have a a 50 VRO, 145 psi each cylinder)
No idle?

Shoot it.

 

[Scottycat]

Re: 87 Johnson 40HP VRO starting/running question

oh and he mentioned he left his key on, that is why the battery was dead.

 

[strosk]

Re: 87 Johnson 40HP VRO starting/running question

Scottycat, thanks for the advice!

I drained and replaced the oil in the reservoir 3 weeks ago and I've run through 3 or 4 tanks of gas since then as well. I've also been using Startron fuel treatment to stabilize the ethanol. I can count those things out right away.

It makes sense to clean and rebuild the carbs. I'll start down that road. I've been wanting to rebuild them anyway. They were professionally cleaned, about three years ago when i bought the boat and the mechanic said he had to do it twice they were so bad. The boat had sat for 4 years with fuel in them. It's ran fine since then, though. It's just odd to me that the motor ran great, then failed while sitting in the garage.

I'll check the compression and change out the plugs as well.

Jtexas, thanks for the battery info. It must have been my trim gauge that drained it. Just wanted to make sure there was nothing electrical that could have "burned up" leaving the key on like that. Thanks!

 

[Scottycat]

Re: 87 Johnson 40HP VRO starting/running question

You will be a carb ace when this is over.

I can have my carbs off and dissassembled in 15 minutes, and I am giving myself 5 minutes to drink a miller light.

You'll see.

Just make notes the first time and only take one carb apart at a time, until you get comfortable with the locations.

 

[strosk]

Re: 87 Johnson 40HP VRO starting/running question

I got pretty good at removing and cleaning an ATV carb, so hopefully it's not much different. Maybe with a little luck I can get the motor to idle better as well. It's never wanted to putt putt along without stalling out. The boat mechanic said that engines never been a good idler, but I know it should be better. I've just lived with it up until now.

Since I'll be at this a little longer, I better grab a sixer of bud light lime

 

[strosk]

Re: 87 Johnson 40HP VRO starting/running question

Hope someone is still watching this... a little slow, but I have an update.

Ordered the carb rebuild kits from iboats, should be here any day. In the meantime, I wanted to be sure I was getting gas to the carb. Pulled the fuel line off the top carb and cranked the engine. Fuel squirting everywhere, so I think it's good to the carb. Next, I pulled the bowl drain screw. I expected fuel, but nothing come out. Shouldn't there be some fuel in there? I then started taking pictures of everything cuz this will be the first time I pulled the carbs off. When I got looking, I noticed a crack. I'm not sure how to post a picture, but I will try to explain. Looking at the carb throat, there's a brass rod that goes up through the middle of it. The rod goes through a brass insert in the bottom of the carb throat. The brass insert is what's cracked. I would think the rod should be centered in that insert, but in both carbs, it's right up against the front of the insert, so much so, that I think the pressure of it being jammed against the front is what crack it.

Let me know what you guys think...

***UPDATED with picture***

 

[jtexas]

Re: 87 Johnson 40HP VRO starting/running question

Did you prime the fuel line with the primer bulb before starting your tests? If so, when you pulled the fuel line off the carb, the gasoline probably drained out of the bowl. Try this: squeeze the primer bulb till firm, then take the drain screw out. If there's no gas in there now, you'll know for sure that the float valve is stuck shut. There's a replacement in the kit, change out the needle and seat both.

Those inner nozzles deliver fuel to the idle jets at the top of the venturi; it doesn't really matter where they ride inside the outer, they take up the same amount of space regardless.

Somebody correct me if I'm wrong, but I don't think the inner nozzle is heavy enough to crack the other, no matter how hard you knock 'em together.

I'm having a hard time figuring out what effect that crack might have...seems like it would affect high RPM if anything.

 

[strosk]

Re: 87 Johnson 40HP VRO starting/running question

Thank you everyone for your advice. Both needles were stuck shut when I pulled the carbs. The top carb had fuel residue, but the bottom carb hadn't seen fuel for some time. I cleaned both thouroughly, replaced everything I could from the kit and the motor is running just as good as she always did for me.

This was the first time taking apart these carbs. I noticed there doesn't appear to be any low/high speed adjustment. Very simple carbs, but how would I ensure my idle is correct?