Mercury 150HP Blackmax Engine RPMS racing up with no throttle

[kcoleman10]

Hey Guys,

I got a mid/late 80s Mercury 150HP. Oil Injection was removed. As soon as you fire the engine up the rpms race to the moon. The butterflys in the carb are closed. I was looking for other obvious things that could contribute to this but I'm not seeing it. Has anyone come across this or know of the answer to this. I was looking for air leaks as a friend of mine suggested but didn't see anything jumping out to me. Appreciate the help.

Kyle

[transomstand]

Broken/Disconnected/stuck trigger

[Sonik]

:iagree: If it ran before the removal, then the trigger has to be the culprit as Pete said..

[transomstand]

Well.....could be a brick on the gas pedal too:cool:

Go home and get your prop..errr my prop:confused:

[kcoleman10]

Ill check the trigger again. I glanced at it quick this morning before leaving for work and something didn't look right in that area. The linkages looked as if they weren't in the right location but I didn't check into it too much. Ill start there.

[wired247]

Are all the butterflies to all the carbs completely closed? Did you just remove the oil injection? If so did you plug the pressure port for the oil tank?

[kcoleman10]

The butterfly's are completely closed. The oil injection was already removed. There are 2 nipples on the oil pump. One is blocked off the other is not. They just stuck a short peice of hose on it with a bolt in it.

[lbhsbz]

What about the fitting in the side of the block that pressurized the old oil reservoir? Did you plug that too?

[kcoleman10]

That one is blocked. Has a brass plug in it.

[wired247]

Is there a rod sticking out the side of the block creating a hole air could enter from?

[transomstand]

Is there a rod sticking out the side of the block creating a hole air could enter from?

Don't be ridiculous, don't you think he'd KNOW if it was only running on 5 cylinders???? Geez:rolleyes:

[tlwjkw]

is this tha first time ya started this motor or have ya run it before?

[kcoleman10]

I haven't run it before. I knew the guy was having a problem with it 2 years ago and he left it sit since. I just recently bought the engine and the boat went to the landfill.

[tlwjkw]

see if its got any jets in it...........

[kcoleman10]

No Jets. Unreal.

[j_martin]

Some configurations don't use the vent jets. That's probably normal.

Look at the throttle linkage. The top of the long arm moves the trigger, radically changing the timing. At closed throttle the trigger should be close to it's minimum mechanical limit. On most engines the timing moves quite a bit before the throttle pick up cam even begins to open the carbs up. Best bet is something is broken/jammed there.

Your description of the oiler delete shows that this engine is the victim of sloppy maintenance.

[tlwjkw]

those don't mater much. check idle's.

[kcoleman10]

Here is where everything is lined up now. The arm for the trigger is back the whole way. I can pull it towards the carbs(front of motor) but then it just springs back to place until the screw almost hits the stop on the block.

[1BadAction]

Here is where everything is lined up now. The arm for the trigger is back the whole way. I can pull it towards the carbs(front of motor) but then it just springs back to place until the screw almost hits the stop on the block.
The stop screw is adjusted improperly. That timing arm is where it should be at WFO.

[kcoleman10]

I'm wondering if spring is jacked up behind the main bolt that holds the linkages on. Ill have to check that out. As it sits now with the arms the carb butterflys are shut.

[1BadAction]

I'm wondering if spring is jacked up behind the main bolt that holds the linkages on. Ill have to check that out. As it sits now with the arms the carb butterflys are shut.
No, the spring is fine.The timing arm idle stop screw is not adjusted properly, it is turned all the way out, it should be turned nearly all the way in. Get the timing arm close to lined up with the split in the case and fine adjust it in gear idling from there. I would also check WOT timing, it's probably ****ed up too.

[transomstand]

Call the Guiness book for a world record. Worst link and sync job in the history of Merc outboards.

[transomstand]

Honorable mention for the job on the oil pump.

[1BadAction]

Call the Guiness book for a world record. Worst link and sync job in the history of Merc outboards.
Funny this thread pops up not 2 hours after I mention lync and sync on that other site. Seeing how that is, I'd be going through everything on that motor with a fine tooth comb, especially the timing and jetting.

[kcoleman10]

I'm still trying to figure out how someone would have F'd this thing up so bad.

[roadkill636]

#5 and #6 are sucking in WAAY too much air !

[roadkill636]

Hey Guys. I was looking for air leaks as a friend of mine suggested but didn't see anything jumping out to me. Appreciate the help.

Kyle
I see something jumping out at me

[kcoleman10]

Are you referring to the bolt hole where the shift mount is?

[transomstand]

I see something jumping out at me

Yea sure, just because the bottom carb is falling off:rolleyes:

[kcoleman10]

I pulled that carb this morning to take a look. Just didn't bolt that back on for the picture

[j_martin]

RTFM, or find someone that can. The linkage is assembled wrong. That arm should be all the way the other way at idle. The "Link and Sync" being referred to is the timing and carburetor linkage adjustment procedure. It's a little different here and there for different engines, but the principles are the same. Both the principles and the specifics are covered in the Mercury manual, with pictures.

[tlwjkw]

first rule/suggestion.... ya gottta at least have tha oem manual if ya gonna do stuff yourself and have no clue which way ya goin'. at least then ya can identify tha parts that are discussed and/or described. some are good at knowin' what a "thingy or do-dad" is and some not so good.........jmo