Need some advice-outboard stalling

[Brownie]

Need some help here. I have a 1995 merc 150 blackmax. The boat idles fine and runs great at wot. The issue is when I rev the throttle to around 2k rpm or higher and cut it back to neutral it stalls. It does this in neurtral and in gear. If I bring the throttle back gradually, it's fine. I wouldn't be so worried about it if weren't a safety issue as it happens the most when I'm docking. Here is what I've done so far.

seafoam decarb
replaced spark plugs
replaced water/fuel filter
rebuilt carbs
replaced 2psi crankcase check valve (this was for a seperate smoking issue)

Here is what else I'm going to try

replace inline fuel filter under cowling
replace primer bulb

Any thing else I should be looking at or replacing as a possible fix. Any help is greatly appreciated!

 

[DaleH]

FYI, that is THE classic symptom for when carb idle points need to be adjusted, i.e., too lean.

All carbs need to be adjusted in the water, NOT on a hose. COUNT where each adjustment screw is BEFORE you start by turning each screw in the X number of turns, writing it down !!!! and then backing it out to where it was.

Warm it up good, do not do it cold. Adjust each for point between too rich or too lean per the OEM manual if you have access to one. Usually one goes turns in for the highest rev RPMs @ idle, then back it out 1/2 a turn. Then do next carb, then go back and re-check all.

Then get off the dock and be free ... then power up and back off ... is she stalls again, repeat the sequence. Most fail to go back and don't realize it takes ALL to make it run good. If this fails, it sounds like the motor needs a "sync and link" tune-up by a Pro. Oh, but check your plugs too, as they should be properly gapped before doing this ...

 

[Brownie]

Thanks Dale! I was somewhat afraid of that. I was pretty careful of resetting those pins when I put the carbs back together. Quick question, the engine idles around 800 rpm's which is where it idled before this isssue popped up. Would it still idle normally if the idle point were out of tune?

 

[windknotnc]

Is that 800 on the hose or in the water...Dale's point of adjusting in the water is huge. I have adjusted on the hose before and put it in the water and lost 100 rpm which made it run crappy. My Mercs in the past idled about 750 in the water and close to 900 on the hose.

 

[Brownie]

that's 800 rpm's in the water.