1976 Mercury 850 carb issues

[72MFG850]

First I am new to the forum and can tell this is a good group to be apart of.
Thanks to everyone for taking the time to read my thread and for any help you can offer. So here I go

I have a 1972 MFG Gypsy15 with a 1976 Mercury 850. Having issues out of the carb. Runs great at idle ( alittle high on the RPMs but ok ) also runs great above 2200 RPMs but while accelerating in the range from 1500 - 2100 RPMs if falls on its face and will stall out. Once you get to 1500 RPMs and it starts to fall if you hit the electric choke and accelerate to 2100 to runs fine ( found out by accident ) I have never really worked on 2 stroke boat motors, always worked on cars as a career and hobby but know nothing about boats. from what All I have read it seems my issue is in the mixture but cant find a diagram to show me where the mixture screws are. Talked to a local shop and they said they would get it right but would run about $300 and I just thought that was alittle pricey. Thought I would seek some advice and see if I could figure it out and fix it. Thanks for reading guys

 

[72MFG850]

Should I start here?

http://forums.iboats.com/forum/engi...ing-and-sync-of-merc-inlines-to-1988?t=168855

 

[Chris1956]

Sounds like the idle mixture is a little lean. OK, so put the boat in the water and start and warm the motor. While idling in gear, open the top carb idle mixture screw 1/8 turn and try to accelerate. If no good, open the lower carb idle mixture screw 1/8 turn and try to accelerate. Repeat sequence until idle quality is acceptable and acceleration is good.

 

[72MFG850]

just to double check the idle mixture screw is the one on the front of the carb on the right ( jet is on the left )

 

[72MFG850]

So I got the idle mixture correct and runs like a scalded dog out of the hole. Now I have idle issues and I think someone tried to make a hotrod out of this motor. Any Idea on how to fix. Problem is to high of a idle

 

[72MFG850]

Don't know if you can see that but someone has cut a piece of the timing arm off, Im assuming to get more timing. Im at a loss of words

 

[Chris1956]

I cannot see the picture. It is too small. You will want to check the timing. I would expect you will want 2-5* ADTC at idle pickup and 21* BTDC at max RPM. Idle speed itself is controlled by the idle stop screw. Back that off and adjust the throttle cable to push the throttle closed, when in neutral.

 

[72MFG850]

OK its in time had a friend set it who deals with boats. I have found my issue, the bottom carb isn't pulling air at idle like the top. I've taken it a parts cleaned all the jets and everything is very clean with no trash still same thing ideas anyone