85hp Merc runs with muffs / dies in water/gear

[jayhawk5]

have a 77 merc which runs great with muffs / shift into gear and will rev up out of water. Put in the water - starts and idles great, dies after shifting into gear.

Have done carb kits / cleaned carbs good. Gas is new, with a new gas line.
Any thoughts / help out there?

KC5

 

[fishinhardwater]

Re: 85hp Merc runs with muffs / dies in water/gear

ever try leaving it on the trailer and starting it up and giving it throttle in gear??

 

[jayhawk5]

Re: 85hp Merc runs with muffs / dies in water/gear

yes, have left on trailor, also now have in driveway in stock tank, does same as in lake. been reading other similar problems and sounds like I need to adjust idle / fuel mix to possibly resolve.

compression test good, and also all wiring has been replaced. this is a time consuming / costly for a novice...

 

[fishinhardwater]

Re: 85hp Merc runs with muffs / dies in water/gear

yea the carbs need adjusting... its not getting enough fuel or air or something when its under a load, but runs fine when the props spinining with no resistance.. try adjusting the screws on the carbs while someone else drives your boat.

 

[Chris1956]

Re: 85hp Merc runs with muffs / dies in water/gear

KC5 - The idle mixture is not correct. Those motors need a rich mixture or they cannot accelerate. If the motor runs smoothly at this point, try richening the idle mixture by opening the top carb 1/8 turn. If it doesn't accelerate smoothly, open the bottom carb 1/8 turn and try again. Repeat the sequence if necessary. You are done when you can make the idle mixture rich enough to accelerate smoothly, and still have decent idle.