Is This a Reed Valves problem in 85 Merc 75 hp Outboard

RiverKnight

Cadet
Joined
Apr 20, 2011
Messages
20
What are reed valves in my 85 Mercury 75 hp outboard and how hard are they to replace. If reed valves were damaged how could that happen and and what would the effects of damaged reed valves be? My motor runs good when you first get in the water but after the motor warms up when you stop and then engage gear again it wants to stall or bog. I can still get it to go by playing with throttle and I can hit choke while giving it the gas and it takes right off. Cranks every time and runs smooth in idile and runs great at speed just problem taking off. Compression is good also, can run all I want as long as I keep moderate speed no prob. just on take off , does this sound like reed valves problem?
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: Is This a Reed Valves problem in 85 Merc 75 hp Outboard

No, it is not the reeds, they are one-way flapper style air valves in the intake that prevent the intake charge from blowing back out the carb while the piston is on its down-stroke.

Poor acceleration + good idle (seemingly) + good top end = is usually a problem in the idle circuit of the carb, getting dirty and not flowing enough fuel.

You could try backing out the idle mixture screws just the width of the screwdriver slot, but it would be better to properly clean the carbs as you can't know what else may be getting restricted and you do NOT want to run your motor lean, that will melt pistons and spoil your whole weekend.
 

RiverKnight

Cadet
Joined
Apr 20, 2011
Messages
20
Re: Is This a Reed Valves problem in 85 Merc 75 hp Outboard

Thanks for the advice CharlieB, glad to hear that this is not a REED VALVE problem.
 

Wingedwheel

Lieutenant Junior Grade
Joined
Jun 16, 2009
Messages
1,071
Re: Is This a Reed Valves problem in 85 Merc 75 hp Outboard

Riverknight, For future reference. A symptom of bad reed valves is gas pouring out your carb from leaking back-cylinder pressure.
 

RiverKnight

Cadet
Joined
Apr 20, 2011
Messages
20
Re: Is This a Reed Valves problem in 85 Merc 75 hp Outboard

Thanks WingedWheel , I appreciate the info, this is a great site and any information I aquire in the future I'll be sure to post so I can hopefully help someone.
 

donzi gt230

Petty Officer 3rd Class
Joined
Jul 19, 2010
Messages
92
Re: Is This a Reed Valves problem in 85 Merc 75 hp Outboard

Another symptom I learned the long hard way is hard starting. This was on an old Johnson V-175.
 

RiverKnight

Cadet
Joined
Apr 20, 2011
Messages
20
Re: Is This a Reed Valves problem in 85 Merc 75 hp Outboard

OK , Marine Service Center called , said they found the problem , said it is the carbs and they doing a carb rebuild on my 85 Mercury 75 hp , supposed to get it back Monday then I'll know for sure , hoping they got to the bottom of this...lol... but I can't be sure till it's back in my hands if you know what I mean..One thing I can tell you if they do got it right it's better to just take your boat to the top Service Center you can and forget the cheap way out cause they never get it right.
 
Top