Mercury dies when putting into gear

[Jackson777]

Hi guys, new here and somewhat new to boats so be easy please.
I have a 1984 Mercury black max 150hp that runs great at high speeds but has a couple issues... Idle is a little rough, not terrible but a little rough and the real concern is that it dies often if you try to give it just a little gas when you put into gear... You basically have to let it idle for a minute and then give it a lot of gas... This is problematic at times like when trying to dock. I am guessing maybe adjust idle? Or fuel filter? Or carb cleaning? Or all the above? I am not familiar with boat motors - decent with land vehicles though. Just wondering if this rings a bell with anyone before I start randomly doing things. This motor is new to me and looks like it hasn't been serviced in a while (got it cheap). Wasn't sure if I should just take it in for tune up or what. In north Texas if anyone can recommend anyone. Sorry for long post. Thanks in advance to anyone that can help!

 

[kmarine]

Sounds to me like dirty pilot jets. Outboard motors use fuel for lubrication as well as 2 stroke oil. Better to rebuild carbs than replace burnt pistons in engine. After rebuilding carbs adjust idle and fuel mixture if necessary.

 

[MH Hawker]

I would start with running some sea foam through it to clean the carb and fuel system and then see

 

[Jackson777]

Thank both of you gentlemen for your replies!
To do the seafoam do I just pour into gas? I know when I seafoam cars I always did it through the break booster.... Man it would smoke good: )

 

[racerone]

Start with a " no money spent " compression test.

 

[Jackson777]

I search for those words and couldn't find anything. Could you please elaborate?

 

[MH Hawker]

A 2 oz per gallon in the fuel is used to clean the fuel system, and the original purpose for sea foam and it was developed for 2 strokes.

 

[Dukedog]

Hi guys, new here and somewhat new to boats so be easy please.
I am guessing maybe adjust idle? Or fuel filter? Or carb cleaning? Or all the above? I am not familiar with boat motors - decent with land vehicles though. Just wondering if this rings a bell with anyone before I start randomly doing things. This motor is new to me and looks like it hasn't been serviced in a while (got it cheap). Wasn't sure if I should just take it in for tune up or what. In north Texas if anyone can recommend anyone. Sorry for long post. Thanks in advance to anyone that can help!

Just readin' this part says, if ya gonna try these things (along with other problems) yourself, first thing ya gonna need is an OEM manual for your motor. Other wise ya gonna be a "lost puppy" when suggestions are made ona key board......jmo

Where in N. Tex.? Know a coupla guys......

 

[Jackson777]

In borger... Looking to get oem manual... Just have not had time to get to it.

That said, I think test compression and add seafoam without a manual lol... But I agree... If it needs a carb tear down/rebuild I probably won't do it with a manual

 

[aussieflash]

Idle in water,just in gear should be 700 - 800 rpm...On flusher (no back pressure) 900 - 1000 rpm.Check that and adjust.I believe the only way to clean carbs is to remove and break them down and clean all metal parts thoroughly in carb cleaner.Always replace gaskets when cleaning and re adjust floats.
Obviously check compression, spark in all 6 cyl first.

 

[Dukedog]

You wasn't kiddin' 'bout "North Tex" was ya! Sorry, can't help ya up there.

These things aren't that complicated. Just gotta know what screws ta turn and what screws not ta turn. If comp is good, sea foam don't work carbs probably need cleanin' with new gaskets inside and out. Maybe tweak tha floats if required. Gasket kits cheap and easy ta do. Idle circuit jetting, off idle jetting (mains). No adjustments (air or fuel) necessary. Do not turn any screws on any of tha linkage on tha side of tha motor or throttle/timin' arm till ya get it back together. Ya might get lucky and not hafta change anything......Might need ta bump idle timin' a tad. Idle timin' is tha ONLY WAY TA CHANGE IDLE SPEED.........

Carb gaskets for any "WH series" from '83 up will work. I'll send ya pm with parts "blow up" and list......

 

[Jackson777]

Thanks Dukedog!! Good man.
I am going to try to check compression this weekend and hope that's good... Does anyone know the torque specs for plugs when I put them back in? That is one of the reasons I should get a manual asap...

As for working on the carb... Don't know if i will even attempt it lol... Got my butt kicked by a 250cc Honda 2-stroke and it has scared me from messing with them!

 

[Chris1956]

Jackson, That motor should have 3 two bbl carbs. The older ones (like yours) sometimes had fixed idle and high speed jets. So just clean up the carbs and go. The newer ones have six idle adjustment screws. It takes some patience to get the idle adjustments right. They must be adjusted in the water, with the motor warm.