Should i inspect reeds?

[199675hpforce]

My outboard runs fine at higher rpms but when idling it ends up stalling after awhile. I installed new carb kit,fuel diaphram. Crowley marine shows there are three reed blocks is this true? Only one carb on this motor also could it be fuel return check valves that screw into block.

 

[pnwboat]

Re: Should i inspect reeds?

I assume that your motor is a 1996 75 HP per your log in ID?

Yes I believe you are on the right track. Try checking the easy simple things first.

1. Compression. You should see no more than a 10% variation in readings from lowest reading cylinder to highest reading cylinder.

2. Check your spark. You should have a good blue colored snappy spark to all plugs.

3. Like you mentioned, check the fuel return valves. Easy to clean them. Take them out and give'em a shot of carburetor cleaner. Don't do this while they're installed in the block. If one is bad, you might end up squirting carb cleaner into the crankcase area. 2-stroke motors don't like to have carburetor cleaner squirted into the crankcase area. Washes the oil off the bearings. You can test them by blowing or sucking on them. They should only flow in one direction.

4. Reed valves would be the last thing to check. This is a little more involved because you have to remove the carburetor and carburetor adapter or manifold to get to them. Late model motors are more prone to breaking or cracking a reed valve than the earlier model motors. After you re-assemble everything, you'll need to check the throttle linkage to the carb to make sure the throttle plate is closing and opening all the way when you move the throttle control.

NOTE: Check this site out. They're usually a bit cheaper, but you need to call them before hand to make sure they're in stock. Even if they have to order the parts, it usually doesn't take that long.

http://www.boats.net/parts/search/Merc2/Force/75%20H.P.%20%281996%29/0E138600%20THRU%200E202999/FUEL%20INTAKE%20SYSTEM/parts.html

 

[john from md]

Re: Should i inspect reeds?

First of all, these engines never really idle well. They were designed to be run at WOT most of the time. If it is loading up at idle, it may be one or all of the following.

1. The idle rpm is too low. Your engine should idle @ 750 rpm in gear. Tie it to the dock and see where it is.

2. The idle mixture is too rich. Don't turn the screws in below 7/8 of a turn out from fully closed as you can burn a piston.

3. The fuel recovery circuit is clogged or there is a leak in the vacuum lines.

Chrysler/Force made several different fuel recovery circuits so you have to look in the manual to see which you have. You may need to clean out the orfices or small reed valves on the side of the engine. NOTE. THESE ARE NOT TO BE CONFUSED WITH THE REED VALVES LOCATED BEHIND THE CARBS.

While Fuel mixture reed valves can cause problems, most of them are noticed at high rpm. Shutting off after idling is not one of the symptoms normally attributed to bent or damaged reed valves.

John

 

[199675hpforce]

I did have a look at few elbow parts for fuel

I did have a look at few elbow parts for fuel

They all seemed hollow inside, i do have clymers manual but is tough to use they go over every dam engine and year.


Ok here is part i belive

http://www.crowleymarine.com/mercury_parts/2014/5.cfm

 

[john from md]

Re: Should i inspect reeds?

You need to pull that long vertical plateoff and check the reeds inside. There are two gaskets that will need replacing when you do this.

Blowing air through the elbows doesn't tell you anything except the elbow is clear. The plate covers another plate that has reeds covering the holes. If the reeds are stuck, the engine can't burn the excess fuel in the crankcase and it starts to load up.

John

 

[Frank Acampora]

Re: Should i inspect reeds?

Typically, because of the large amount of air inducted at full throttle, an engine with one or two broken reed petals will run fine at high RPM but produce less than maximum power.

However, because of the limited amount of air inducted at cranking speeds, blowby past the broken reed petals is much greater percentage-wise than at high RPM. This can make starting problematic. If the engine starts well but doesn't want to idle, as stated above, checking the reeds would be the last thing to do.

The FIRST thing I would do is to check and/or clean/replace the sparkplugs and the second thing is to make certain the idle speed is set high enough.