Engine cuts out when put in neutral or reverse

[donnaceala]

I have a 1986 Mercury 35hp engine which starts up fine but as soon as I put in neutral or reverse (to get it off the trailer) it dies. I've had carbuerator cleaned and run Sea Foam (which helped 1 time but not since) but still can't get it off the boat. It will not run at an idle in neutral. I noticed that the top spark plug wire was jumping fire. So I am going to replace this tomorrow. Would the spark plug wire stop the engine from going into neutral or reverse? I am trying to get the boat (pontoon) fixed so I can sell it and don't want to put a lot of money into it. Whenever I do get it out it runs hard but just can't seem to get in to go in neutral or reverse so it can be test driven.

 

[aussieflash]

Re: Engine cuts out when put in neutral or reverse

Check your idle,sounds too low.Shouldnt you be starting it in nuetral??Or are you saying it wont idle when you choke/throttle down?

 

[donnaceala]

Re: Engine cuts out when put in neutral or reverse

The boat won't start in neutral. Have to have throttle pushed at least a qtr passed neutral and let run for a few minutes then when I pull back to neutral it dies.

 

[FLATHEAD MAC]

Re: Engine cuts out when put in neutral or reverse

Sounds like neutral switch if it wont start in neut. Tiller or console control?? if console controll might check internal wiring for possible short out when pulling back to neutral and not shorted when just forward.

 

[donnaceala]

Re: Engine cuts out when put in neutral or reverse

It is console control. We took the boat to the lake Saturday and put some Sea Foam in the carburetor thinking that this would help. It actually did stay running in neutral for quite awhile while idling. We took the boat out and road it hard for about an hour and when we came in and got close to the dock the boat cut off at low idle. Again it did not want to go in Neutral (luckily we were close to the dock) We took the boat out Sunday and it would start up fine but would not start in neutral. I had to have throttle engaged. When trying to bring it back down to neutral it just dies. Couldn't take it out since we couldn't get it off the trailer.

 

[MercMan82]

Re: Engine cuts out when put in neutral or reverse

Have you checked compression?

 

[CharlieB]

Re: Engine cuts out when put in neutral or reverse

I have a 1986 Mercury 35hp engine which starts up fine ............ I've had carbuerator cleaned ............... It will not run at an idle in neutral. .................

Very often after cleaning carbs, motors are started and carbs adjusted while on the GARDEN HOSE.

Idle mixture MUST BE reset once ON THE WATER, as the addition of water in the lower leg, and exhaust passage, causes the motor to need additional idle mixture fuel.

Take your scredriver with you, turn each carb idle mixture screw out (CCW) 1/8 turn, launch the boat and try again.

Once running on the water, idle the motor in Forward gear and readjust each mixture screw in/out til the motor runs at the best possible speed. Take your time as it can take up to a minute to burn off any excess fuel after each adjustment.

Once running/idling at 'Best Speed' in Forward gear, further open each screw another 1/8 turn to provide the additional fuel needed for crisp acceleration. Test by rapidly opening the throttle WOT. Any hesitation of bogging indicates a need for even more idle fuel, open each again just the width of the screwdriver blade slot and retest acceleration. Repeat to perfection.

Take your time, once done your motor will run great.

 

[aussieflash]

Re: Engine cuts out when put in neutral or reverse

As i said...check your idle.Another thing is possibly a stuck choke/flooding.

 

[donnaceala]

Re: Engine cuts out when put in neutral or reverse

Thanks, Captain CharlieB! I am going to try your tips this weekend. I will definitely let you know how it works out! I greatly appreciate the feedback.

 

[donnaceala]

Re: Engine cuts out when put in neutral or reverse

Thanks for all the responses!!! Based on the feedback it is either an idle problem, neutral switch, or a stuck float. I will test the idle this weekend and provide feedback in hopes this might help others with the same problem.

 

[rivermouse]

Re: Engine cuts out when put in neutral or reverse

Having the carb "cleaned" is vague. Did you disassemble it and make sure every passage way is clean?Sea foam often wont help a clogged up idle tube . Did you rebuild the carb? Also replace the wires and inspect the plugs.

 

[donnaceala]

Re: Engine cuts out when put in neutral or reverse

Having the carb "cleaned" is vague. Did you disassemble it and make sure every passage way is clean?Sea foam often wont help a clogged up idle tube . Did you rebuild the carb? Also replace the wires and inspect the plugs.

I paid a boat mechanic $250 a couple of months ago to rebuild the carb and replace with new fuel lines because I thought the problems was due to the carb. I replaced plug wires and plugs yesterday and didn't help any.

 

[donnaceala]

Re: Engine cuts out when put in neutral or reverse

Have you checked compression?

I am not sure what the compression should be for this motor since I don't have a manual. I have a compression tester but don't know what the compression should be.

 

[MercMan82]

Re: Engine cuts out when put in neutral or reverse

Sounds like neutral switch if it wont start in neut. Tiller or console control?? if console controll might check internal wiring for possible short out when pulling back to neutral and not shorted when just forward.

After my post, I Missed the part about it Running fine, from your first post. Compression should be over 100psi and within 10% of each cylinder. I agree with Mac, check neutral switch.

 

[donnaceala]

Re: Engine cuts out when put in neutral or reverse

Checked the compression. Both cylinders at 100psi. Replaced both spark plugs and wires. Took the boat out today and put it in the water to adjust carb. Adjusted 1/8 turn and tried multiple times but boat would not stay running when cranked in neutral so we never took it off the trailer. It will crank and run good in gear but boggs out when put in neutral. Since it has cranked in neutral (several times but very difficult) but won't stay idled would this be the neutral switch? Is there anyway to check the neutral switch? Is there a chance that the carb needs rebuilding again (just had it done a couple of months ago). Boat had same problem when we got it out of the shop after carb was rebuilt.

Someone that was interested in buying the boat came by to look at it and brought a mechanic with him. He said he thought it was the fuel pump. I am about ready to give this boat away if I don't set it on fire first

 

[MercMan82]

Re: Engine cuts out when put in neutral or reverse

No, if it were neutral switch, it would not start at all, which begs the question, how are you able to start if not in neutral? That's the purpose of the neutral switch correct? Most likely carbs or fuel pump or anything related to fuel. I'd bet on your idle jet adjustment. Mark the spot where it's at with a marker or something and turn clockwise till lightly seated counted the full rotations. Manual suggests starting adjustments at 1 & 1/2 turns from bottom. Check it and see where you stand.

 

[aussieflash]

Re: Engine cuts out when put in neutral or reverse

So your saying it starts in forward gear???forward gear???..didnt think that was possible.So prop spinning when starting??Im guessing your terminology is a little off.
I think your trying to say...You throttle up in NEUTRAL to start engine,then when you bring throttle back to IDLE it dies.....IDLE is not NEUTRAL....If this is whats happening then start with your idle adjustments.The best investment for you is a MERC service manual....PRICELESS!!

 

[donnaceala]

Re: Engine cuts out when put in neutral or reverse

So your saying it starts in forward gear???forward gear???..didnt think that was possible.So prop spinning when starting??Im guessing your terminology is a little off.
I think your trying to say...You throttle up in NEUTRAL to start engine,then when you bring throttle back to IDLE it dies.....IDLE is not NEUTRAL....If this is whats happening then start with your idle adjustments.The best investment for you is a MERC service manual....PRICELESS!!

Sorry for the confusion. Yes, when returning to "idle" is when the boat dies. It has run a "few" times when bringing throttle back to idle but I have to put in gear VERY fast. When bringing the boat back to the dock the boat cuts out when idling. I purchased a manual today

 

[donnaceala]

Re: Engine cuts out when put in neutral or reverse

Took the boat to the shop. The problem was a hole in the fuel pump diaphragm. Part costs $12. Mechanic fixed the boat and bought it : )

Just wanted to give update in case others have this problem.