question on reed valves

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stackz

Master Chief Petty Officer
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ok, so I took the carbs off my 1990 90hp mercury engine to rebuild them and while they're off I decided to get a flashlight and look at the reed valves.

they are the ones that look like a flower petal setup when you look at them installed. I'm trying to determine if I need to replace them or not.

the top carb set had 2 that naturally sit about 1~2ish mm from flush. are any reed valves that dont sit flush against the housing considered bad?

one of them also had surface rust on it.

I saw a couple more that werent exactly flush on the other two and the lowest set has some oil mix just sitting on it...which is why I pulled the carbs off in the first place to rebuild.

I would run the engine and shut it down and then oil mix would come out of the lower two carb throats and settle into the air intake box. when I'd crank the engine up, the carbs would suck the mix back up and the engine would bog down until it was all burnt and running on regular mix.

I'm just wondering if the reed valves should be replaced or how to tell when they're bad or not. I'm already in there so it wouldnt be too much more to replace them.
 
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Maxz695

Guest
Re: question on reed valves

Gas sptting out of the reeds is a sure sign they are not sealing properly. Rust indicates water intrusion either through the lower crankshaft seal or through the exhaust divider plate. (Baffle) Be sure it,s not the carb float level or a needle seat that is not functioning properly before taking it apart. If you turn the engine over without the carbs off there should be no back pressure from the crankcase through the carb ports. This is what would cause the spitting due to bent worn or broken reeds. Usually it is the bottom reed, rod, wrist pin, piston, bearings and crank journal affected by the water damage. Which reed was rusted?It sounds as if you checked the bottom reeds and they where all flush. This indicates that the carb is the issue and not the reeds for the lower cylinders.
 
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stackz

Master Chief Petty Officer
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Messages
830
Re: question on reed valves

the rusted valve was on the very top carb and it was roughly the upper left side when looking down into it. also, should probably mention this motor was submerged under water for two hours about 5 years ago. we got it home, cleaned it all out, ran it and then let it sit for a couple months before using it again. its seen regular use since then and this issue only popped up this year. the surface rust on the valve probably occured during the initial sitting phase if I had to bet.

can I turn it manually or should I use the starter to turn it over.

so turning it over wont cause the reeds to open on the intake stroke? I mean I understand how a reed valve "functions"...one way valve to suck air/fuel in, not let exhaust back out, just havent actually gotten in on an engine where they were ever bad or worn so I dont know the exact tests, what to eyeball...
 
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Maxz695

Guest
Re: question on reed valves

I edited the first post re read it thanks. You can have someone turn the key and hold your palm over the ports individually to check them but you,ll have to remove the plugs and ground them so you don,t get shocked and the engine doesn,t fire on you with any fuel in the case. The intake creates suction opening the reed valve and takes in gas. Then when compressing the fuel the reeds are presurized and seal closed not allowing air fuel to escape the case. You may be right about the rust as it is the top reed and unless it,s terribly rusted shouldn,t be much of an issue. I would think that the rust may affect the reed in time and possibly break off and cause damage to the internal componants. It,s your call and seeing that you mentioned some are not flush it might be a good idea to replace them. JMO
 
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stackz

Master Chief Petty Officer
Joined
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Messages
830
Re: question on reed valves

cool. yeah, thats why I figured I'd ask and test them while I have it apart. pain getting the carbs off and I dont want to do it twice if I have to replace the valves. they're cheap enough as it is so I think I'll test them (just to get experience with it) and replace them anyway as cheap insurance...I can also get a better look inside the crankcase too at this point since I havent had it open since its little water excursion haha.
 
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stackz

Master Chief Petty Officer
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Messages
830
Re: question on reed valves

ok, I'm in the process of finally ordering the parts I need. I just cant tell if the price is per individual or each...

also, the only reason I'm ordering from this place is because when I put in the part #'s on here, iboats says they cant be found?

serial number is OB275426

http://www.**********/parts/search/.../Induction Manifold and Reed Block/parts.html
product_thumb.php


in the exploded diagram it shows the reeds as a single round flower but I was able to do some google searching and it appears they only come as half an assembly like this?

$(KGrHqFHJC8FBkW7e3tKBQmV3yo6qw~~60_1.JPG
 
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stackz

Master Chief Petty Officer
Joined
May 29, 2008
Messages
830
Re: question on reed valves

lol guess their site is blocked here
 
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stackz

Master Chief Petty Officer
Joined
May 29, 2008
Messages
830
Re: question on reed valves

I already have a copy of the service manual though

I guess my main question at this point is if there are any non-mercury replacement reed assemblies versus the 43018a as in sierra brand or something since the part number doesnt show up in the parts search here on iboats.
 
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