150 mariner V6 magnum III cleaned carbs now won't stay running

[mbecke2]

I took all the carbs off today and cleaned them thoroughly with carb cleaner and compressed air. They looked perfect. I put the carbs back on and hooked everything back up thinking it was going to purr. HAHA!! It would pop and start then run for 3 seconds and die. I tried to adjust the timing with no luck. I could get it to start but everytime it started it would kill after 3-5 seconds. I tried opening the carb throats, or reving it up, when it would start and that didnt help. It did scream and rev up a couple times but it would still die after 5 seconds. I could not get it to stay running so I gave up on it. Could it be something I did? Is there an easy test to diagnose this. All three carb assemblies are getting good fresh fuel. I think it could be ignition but not sure.

 

[TD_Maker]

Re: 150 mariner V6 magnum III cleaned carbs now won't stay running

What does the compression look like? Are you getting solid spark on cylinders?

 

[wired247]

Re: 150 mariner V6 magnum III cleaned carbs now won't stay running

Your float levels are probably screwed up.

 

[racerone]

Re: 150 mariner V6 magnum III cleaned carbs now won't stay running

What was the motor doing / not doing that enticed you to clean the carburetors ?

 

[Mi duckdown]

Re: 150 mariner V6 magnum III cleaned carbs now won't stay running

^+1

 

[mbecke2]

Re: 150 mariner V6 magnum III cleaned carbs now won't stay running

I will have to do some more investigating to get all these answers. Last I checked compression was about 100psi on all 6. Motor used to purr like a kitten and run perfect. I havent checked the spark yet and I think the bowls are perfect. I blew(with my mouth) into each carb assmbly and air went through then turned it upside down and it was airtight. Carbs look great like I said. Could it be bad gas?? The motor has not been idling well and plus its spring time, so thats what enticed me to clean them. Last time on the water motor did fine but just didn't idle too good. I tried to get it to idle at about 800rpms but everytime I would get it where I want it, the motor would either idle too low or too high. I think I need to adjust the throttle/timer base linkages and do a link n sync. But now I got new problems!! I will mess with it some more and post results.

 

[CharlieB]

Re: 150 mariner V6 magnum III cleaned carbs now won't stay running

Idle fuel and air bleed passages are smalll and can be a serious PITA to get cleaned correctly. If once isn't absolutely meticulous mineral accumulation can be dislodged and clog a passage. It is critical to use the little red spray tube on a can of carb cleaner and spray thru every passage, followed by high air pressure. Sometimes I have had to resort to using a VERY thin wire to probe thru passages before I could get a stream of carb cleaner to blow thru. Be very careful to NOT get chemical in your eyes.

Wally world super Tech Carb Cleaner is my favorite, about the cheapest I've found (just under $2) yet one of the best chemicals I've used.

Make sure all float levels are perfect and the same as specified in the factory service manual.

There MUST be some clearance between the throttle linkage and the throttle lever roller so that timing is advanced before the carbs open when the control is moved.

 

[mbecke2]

Re: 150 mariner V6 magnum III cleaned carbs now won't stay running

UPDATE: I did some more fooling around today. Compression 100 psi on all 6 and perfect strong spark on all 6. I cleaned EVERY single orifice and jets and even soaked them in B-12 cleaner. I used carb cleaner and compressed air. To me the carbs were PERFECTLY meticulously cleaned in every way. I just can't figure out whats wrong. You'd think I installed them backwards when you hear the motor now!! I can get it to start but it revs really high (scares and wakes up neighborhood) then kills. Cant get it to stay running for 5 seconds. My experience tells me its got to be a fuel issue since compression and spark are fine. Unless its timing but I doubt its off that bad. The float levels on this motor cannot be adjusted. There is a small flathead screw that holds the small stainless steel rod down which holds the float down and you have to screw it in all the way. The float levels appear perfect to me. I also made sure the fuel was fresh. And all 3 carb assemblies are getting fresh fuel. They are filling up with fuel perfectly until the bowls reach the cutoff height. I'm at my wits end and about to bring the motor to a mechanic. Unless there is something stupid I did to the carbs and I'm overlooking, I'm at a loss. Also I even took the 2 metal housings off the top of each carb assmbly and cleaned those. They had needles coming out the side with springs on a flat head screw (not sure what these are) and I took all that apart and cleaned it too. Maybe I messed with something I shouldnt have, but I am pretty sure I put everything back on correctly. Thanks for all the replies!!

 

[CharlieB]

Re: 150 mariner V6 magnum III cleaned carbs now won't stay running

Ah, needles with springs coming out of the side of the carb are idle mixture screws.

These must be adjusted carefully to get the correct fuel mixture If you did not turn them in until lightly seated while counting your turns, then after cleaning put them exactly back to the original setting you will have to start from scratch.

Turn each in until just barely seated, turn carefully, you do NOT want to smash the soft aluminum seat. From lilghtly seated back each on out exactly one and onehallf turns. This should give you enough fuel to start the motor and get it into gear.

From there the prop needs to be in the water, in a test tank, or the boat/trailer backed into the water. This is critical as the water column in the midsection places exhaust back-pressure which directly affects idle mixture.

Start and warm the motor, once warm shift into Forward gear. Adjust each mixture screw slowly to achieve the "best Idle Speed' while in gear. Not done yet. From here the motor needs even more idle fuel for crisp acceleration. If you rapidly open the throttle now the motor will bog and possibly die. Start by opening each one just two times the width of the screewdriver blade slot.

Now test acceleration, take the boat away from the dock and any 'No Wake' zone then rapidly open the throttle. Any bog, miss, or lean cough, proves a need for even more idle fuel. Open each just another blade slot width, repeat acceleration. Repeat until you can slam the throttle from full idle to WOT without the slightest hiccup.

 

[mbecke2]

Re: 150 mariner V6 magnum III cleaned carbs now won't stay running

HALLELUJAH!!!!! Thank GOD for the internet and iboats forum. And thank GOD for Charlie B!! You da man Charlie. As soon as I read your reply I went out and turned the idle mixture screws one and a half turns out. The motor started with half a key turn and ran all day long at 1000 rpms. Purred like a kitten with a full belly of fish!!! I revved it up, went into forward, reverse, neutral. Everything worked and sounded perfect. Now I need to water test it and make sure shes good to go. Cant believe something so simple had me stumped. Once I get those screws right I should never touch them again!!! Again I appreciate your information. I definitely owe you some cyber love. Live and learn!!