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Discussion Starter #1
The motor I have is a 50273C I am not getting fuel to the upper cylinder. I have checked for spark and it jumps a 7/16 gap with no problem. Compression is 115ish on both cylinders. When I rev the engine I can clearly see fuel spraying out of the venturi on the carburetor. When I place my hand over the top carburetor i have suction and fuel will pour out of the throat when I take my hand off. I put new plugs in the motor per specs and gapped at .40 when I removed the plugs I noticed the bottom plug is sooty being that both mixture screws are 1.5 turns out. The top plug is as clean as the day it was installed. Does anyone have an idea what can cause this issue? The motor was given to me and has had this issue since I recieved it.

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US ARMY 2d ID VETERAN
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Okay you're saying the top plug has spark. Is it a strong Blue spark, or a weaker reddish spark?
I'd look at the timing.
Try this, swap the bottom sparkplug wire to the top plug and top to the bottom. start the engine and see if the top cylinder is firing or not.
If it is, your top coil is bad. If it had no effect, look at the timing.

Get a clean 16oz water spray bottle and put a little mixed gas in it (you can use your fuel line and pump the bulb to squirt some premix into the bottle).
Start the engine and while it's running, using the spray bottle with the gas in it, mist the top carb and listen to the engine to see if the top cylinder busts off for a second or so. If not, squirt a stream of gas into the throat of the carb, listen to see if it fires off,
If it fires off, and only runs when you mist it, I'd have to say the float needle valve and/or float is stuck or clogged, or you're not getting fuel to it at all. Rebuild/Clean the carb, also check/replace any bad fuel lines.
If it doesn't bust off, then you don't have enough fire in the plug, go to the coil, maybe bad or weak.
If all that is okay, look again at the timing.
If the timing is out, it'll still fire the plug but not when the fuel is introduced from the carb.
g/l
 

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Discussion Starter #3
The spark is bright blue and will jump a 7/16 Gap. I did swap the coils around already also as well as swap the power pack, stator and timer base from the donor motor in my elimination process with no change. Yesterday afternoon I did place my fingers around the outside of the carburetor and could hear a slight butt instant change in the sound of the motor but it was short-lived. When I would pull my hand away from the carburetor then the fuel would just pour out of the front of the carburetor. When I would rest of my fingers slightly in front of the carburetor I could tell that it was drawing air because my fingers would flutter if that makes sense. Only thing that I am not quite sure about is the timing. But I did verify that the top dead center indicator on the flywheel matches to top dead center of the top cylinder. I removed the top plug several times during the course of the day yesterday and each time the plug was bone dry. Just my thinking but if timing was off and not sparking correctly than the plug should have at least been wet with fuel

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Then I'd have to guess the reed valve. Pull the carb, then the carb plate to get to the reed valve, it'll most likely need to be replaced. Hopefully there won't be any missing pieces that got into the system. Next would be a Case leak, lastly a clogged port at the cylinder.
 

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Discussion Starter #5
I removed the Reeds that were in the motor and replaced them with the set from the donor motor. Both sets of reeds looked to be in good condition. I just looked on Marine engine. Com and the Reeds for my particular motor or unavailable. There are some listed on eBay but then again buying from eBay I'm still taking a chance, is there an aftermarket place where I could possibly purchase them new. I'd rather have a new set of reeds versus another previously-used set. I would also like to know if there is a way to rule out the possibility of a leaking seal on the crankcase halves like you mentioned

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The reeds are very delicate and it's very hard to tell if its good or bad by just looking at it. To check the reed valve, remove the spark plug from the top cylinder. Insert a small hose (like a 3/8" fuel line), tape it around the sparkplug hole so to keep it from leaking. Light a cheap cigar, and blow smoke into the hose into the upper cylinder. If smoke comes out of the carb, you have a bad reed valve. If no smoke comes out, the reed valve is good.
To check for a case leak, it's somewhat impossible, but the easiest is to check around the flywheel for oil/grease. Remove the flywheel and look around the trigger, etc for oil/grease. If none, the upper seal is good. If nasty, it's bad.
To check the bottom (middle split), you'll need to pm me. My way to check it can be dangerous and I do not want to put it on the open web.
To check the cylinder for a clogged exhaust port (from using cheap oil), remove the water jacket, then the plate, there you will see the cylinder. You can check the exhaust ports to see if they're clogged, if so, scrape/clean them.
A point of warning, there's about 15-18 1/4-20 bolts that holds the plate and water jacket. You will most likely break off several of them due to corrosion, unless you have experience with removing corroded bolts. Using a hand held propane torch to heat the casing (NOT the Bolt), then squirt some wd40 or the like around the bolt. Reheat and slowly back the stuck bolt out. If there is Any resistance, you'll have to baby it and repeat heat/oil until you get it, or you'll spend alot of time and money to have the broke ones drilled and tapped out. g/l
 

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I wouldn't buy a new reed valve until you smoke check your motor first, to see if it's bad or not.
 

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I'd also like to complement curdogs suggestions with a cylinder leak down test. You can have compression, but your motor relies heavily on vacuum to make the carbs work correctly. If it leaks down quickly, you could have bad rings or bad crank seals. Follow his suggestion and check your seals.
 

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Discussion Starter #10
I tried checking the reeds using the smoke method. However I used a vape instead of a cigar. The only place I can see smoke is through the prop, nothing through the reeds. I used a compression tester screwed into the head and blew where the coupler would attach. Is there any certain position the piston should be while performing this test? Also I was thinking about 2 other ideas. Could the timing be off so bad that its causing my issue? I did notice that the timer base stop screw/bumper was turned in towards the stop as far as it could go. Also could a bad crank seal be checked by putting air pressure to the cylinder and spraying the seals with soapy water. The hard part would be accessing the bottom seal. If I had to remove the power head then I may as well change the seal anyway I guess.

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Discussion Starter #11
Just an update, this evening I took off the flywheel and attached the compression tester hose to my compressor and adjusted it to around 30 PSI. I sprayed soapy water around the top seal and I had no air bubbles. I also sprayed the area where the two halves of the block would bolt together I had no bubbles there either. I did notice that I was having air leakage coming through the reeds depending on the Piston position just a slight turn of the prop would stop air coming from the reeds. I had a good flow of air coming through the prop so I know the exhaust Port should be open. I would have to disconnect the hose to be able to rotate the prop enough to seal off the air coming through the exhaust. I attach the hose to the number 2 cylinder also and had the same results. Depending on what everyone thinks I plan to reassemble the flywheel and carburetors and spin the motor while leaving the spark plugs out and see if I have any fuel spraying out by doing the paper method on the motor.


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Jaded Old Phart
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So the motor is just running on one cyl? Have you tried squirting gas into the top carb while it's running to see if that cyl kicks in?
Asking because you never said it's running on one cyl, just no gas to that cyl.
 

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Discussion Starter #13
I have. Doesn't change the engine sound at all.

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Jaded Old Phart
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What have you done to the carbs?
 

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Jaded Old Phart
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Plus, was the key on the flywheel intact?

NVM, see it in the pic.
 

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Discussion Starter #16
I have rebuilt both. I ordered another fuel pump also and installed it this evening thinking that the original that I had ordered was bad. So to add to my frustration I have noticed that I have no pulse coming from the crankcase to operate the pump. If I remember correctly the pulse came from the top cylinder even though the pulse line connects to the bottom end of the intake. Currently I am able to get the motor to run by operating the primer bulb, the motor seems to be a hit and miss as far as firing and shakes really bad. if I let the fuel start to run out of the carbs the motor picks up RPM and runs like a scalded dog until it eventually runs out of fuel.. so I'm actually wondering now if by me manually operating the primer bulb if I'm not somehow putting too much fuel to it and actually flooding the engine. Or it's leaning out which is causing the sudden rise in RPM.

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You have to do a leakdown test. And by reading all what you have done, sounds like you gotta tear it down to get to the cylinders and pistons.
Good compression vs % of leakage is the issue. Here's cut and paste:

Compression is the heart of an outboard. If one or more cylinders are damaged due to improper timing settings, lean fuel condition, overheating, or stuck rings from carbon buildup, your outboard is about to become history. Does a compression test alone always determine that my outboard is in good shape? Suprisingly the answer is "no". A good compression reading does not completely determine internal conditions. To correctly diagnose condition of pistons, rings, and cylinders, a leakdown test should also be performed. Using a quality leakdown tester, each cylinder should not show more than 10% loss. If any do, there is certain to be an internal problem in the making. For example, a compression reading of 120 lbs would be viewed upon as a good cylinder by the average person. This may or may not be the case. If a leakdown test of the same cylinder indicates say...20% to 25% or more leakage, it would be a good bet that excessive wear, scored cylinder, the cylinder scratched, and/or the rings stuck or damaged in a way that does not show up with a simple compression check. In any case, wear or damage is present and advisedly requires attention before further damage and/or exceptionally poor performance and efficiency results. Most common effects from diagnosis of excessive leakdown would be in the idle range of the motor. If all other motor functions check out attempting to diagnose an idle problem, then its a good chance that blowby is the culprit. It is advised that leakdown tests should be performed at the beginning of the compression stroke (rings just above exhaust port opening, which is the critical point), and NOT at TDC. Make sure you have flywheel locked down securely when doing a leakdown test. If you try to hold the motor from turning with a socket and breaker bar, you are putting yourself in a dangerous position should the breaker bar slip from your hand. Purchase a compression gauge and leakdown tester to go in your boat's toolbox and check cylinders a couple of times a year to ensure there is nothing unusual going on internally. Using proper grade of gasoline and outboard oil is essential to preventing internal problems. Proper winterization procedures will also do wonders to prolong the life of the internals of your outboard. If compression check shows more than 15 lbs difference on any given cylinder from highest reading of other cylinder/s, or if leakdown test shows excessive loss, you have a problem in the making! DO NOT continue running the motor until problem is diagnosed and repaired! It could result in causing much more internal damage than you already have.
 

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Discussion Starter #18
That's my next step I guess. I will do that and let you guys know what I find out

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Discussion Starter #20
Where abouts are you located? I was going to get one from harbor freight but reading the reviews, their products are usually a hit or miss.

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