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Carb Rebuild

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ajv00303

Regular Contributor
Just rebuilt 3/6 carbs (Starboard motor/Port side) on a pair of 1995 Johnson 175's.
It appears that all (12) are leaking to some degree..........just recently purchased the boat.
I now know the issue w/ the float bowls warping/leaking and the "ball bearing" on the side of the float bowl coming out!

On the other (3) carbs on the Starboard motor I added MarineTex to the spot w/ the ball bearing as I did on the carbs I rebuilt.

Question: when I prime the engine with the "gas" primer bulb, am I priming the carbs w/ pure gas and not 50:1? VRO pump is in tack and appears to be functioning.

Plan on starting tonight!

TIA!
 
Sorry but a VRO will not add oil to fuel using primer bulb, the VRO has to cycle to add oil. Yes you are correct VS will be filled with pure gas but the engine internally has enough oil residue that it can run with no damage. Just remember carb adjustment cannot be set accurately on a hose for the engines….
 
To settle this, a little cranking while priming/pumping the bulb, will present lubricating oil to the system......which is usually the case when attempting a start. Secondly.....on VRO's there is not an oil mix in the carbs/float Chambers. If more force is applied to the primer/squeeze bulb.....no needle and float can really hold back that pressure. You must be reasonable.
 
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timguy said:
Secondly.....on VRO's there is not an oil mix in the carbs/float Chambers.
Click to expand...

This confuses me..........
I understood the "fuel" from the pump going to the fuel rails was mixed w/ oil at that point. If not, how does the oil get into the "mix"?
 
Perhaps I'm wrong....thinking about a different model, sorry. Dah! How's that for a good excuse? Mercuries of the oil injection generation, introduce oil behind the carbs.
 
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??----Yamaha does not mix oil with fuel.----It goes into the manifold after the carburetors.------On Mercury the oil goes into the fuel before the carburetors !
 
Yup, just like I said, Racer.......man, did I screw up THIS post. Thanks. Gonna take my nap now, okay?
 
Well I re-installed the (3) carbs I rebuilt.......no leaks but seems to run worse.
Maybe I need to re-adjust the idle mixture? Will try tomorrow.
 
Tried fooling with it today......seems the more I touch it the worse it runs.
Replaced fuel filter/water seperator and cleaned the fuel filter at the VRO Pump.

Seems like it is starving for fuel. I pre-adjusted the idle mixture at 4 turns out.
I tried adjusting the idle mixture screws to no avail, I had to walk away from it. I bought new plugs but didn't put them in yet.

At this point it will barely run.....need help here. I'm in unfamiliar territory here! I'm a SBC I/O guy! I hear good things about these motors, would like t get them running well. I also verified oil to the VRO pump, disconnected the hose and squeezed the primer bulb to verify oil at the pump.
 
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I stuff some window screen crumpled up in the prop, you can experiment to see what you want. This will of course richen the mixture. I have experimented with this and got it down pretty accurately. My final adjustment is on the water. Once underway, however, ......on the water......you actually LOOSE backpressure as the water flow, when moving forward, helps DRAW exhaust........not "rocket science", buts it's......DAH!
 
Tried again tonight. I re-adjusted all the mixture screws all the way in, then 4 turns out.
Started and seemed to run a lot better, I tried adjusting the mixture screws but did not see much effect........decided to leave it as is until I put it in the water.
Still need to rebuild the starboard carbs on this (starboard) engine, will probably do his tomorrow, just received the kits.

Question re: the carb rebuild: the kit came w/ new needle, seat and float. Also came w/ a plastic washer for under the seat. There wasn't one on there originally but I installed it and adjusted the float so it was level w/ the gasket. Did I do the right thing installing the plastic washer?
 
Yes, the depth of the seat is calculated using that washer. How close was the float level? Did you barely have to tweak it?
 
I retired prior to your 1995 175hp existed, however......

It has always been, pertaining to the idle adjustment, to momentarily gently seat the needle valve, then to back it out whatever turns it states in the service manual.........................
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(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open as per your service manual "X" amount of turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note 1: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.
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Noooooo.....The 60° motors do not use a washer under the inlet seat, they are tightened against carb body, that's why level was high. The motor has to be warm, have back pressure and able to run in gear with a load. Initial carb setting is 5 turns out from light seat. Run engine trimmed level in gear a least several minutes, if it sneezes/pops it lean so open each needle 1/8 turn CCW. If a tad rough its rich so turn needles CW 1/8 turn. Allow at least 15 second for adjust to set in.
 
As you stated in post #16, I would call that a "red flag".Anything more than a "tweak", and I would reconsider. Note, however, the float was new also, but if the float ended up parallel AND THE SAME DISTANCE from the carb surface........you will end up with exactly the proper float level anyway. I just rebuilt a similar carb today, but on a lawn mower. I do small engine repair too......lots of carb work......Minnesota is a HEAVY ethanol State with TONS of humidity.
 
Just cause its parallel and level does not mean it will work. If the tab was not adjusted for float drop the needle will open to late to fill carb.
Question re: the carb rebuild: the kit came w/ new needle, seat and float. Also came w/ a plastic washer for under the seat. There wasn't one on there originally but I installed it and adjusted the float so it was level w/ the gasket. Did I do the right thing installing the plastic washer?​
Click to expand...
No ….you need to remove washers
 
With no intentions to insult or disagree with anyone.... my procedure has always been since way back in time when the plastic carburetors came upon the scene...........

Looking closely at the threaded hole that the brass float needle valve seat screws into.... If perfectly flat, use a washer... If a slight increase in height that resembles the shape of a washer exists, do not use a washer. Works for me.
 
That's good advice. There are modified designs too that use different tapers, or shoulders. Why the washer came with the kit? Probably for different applications, or even different floats. Perhaps there is a bulletin out on this particular carb and/or kit. The ultimate goal, of course, is to present fuel at the correct level. Operation at different trims doesn't seem to create many problems, so it is my belief that exact float level is not as critical as it may seem. Operation, even at full power, may demonstrate trims varied by more than 20 to 25 degrees. How about shallow water operation? It is almost beyond belief that outboards were ever engineered with float type carbs.
 
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Many early outboards incorporated a tiny cylindrical float chamber that could effectively control fuel at drastic angles of operation. Engineering "progressed" and float chamber evolved to more of what we see today. Mercury held on to more traditional chamber design which of course is more friendly to varied angles of operation. Had I been an engineer, I would work with vertical cylindrical float Chambers as well as diaphragm options. Why should you spill out gas when you fully tilt up the motor?
Some people believe that we actually put a man on the moon. I really don't think they hired many outboard engineers.
 
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If you don't want to follow factory instructions and manual just do what ya like or read and maybe it will run...done

ps..the washer is in the inlet kit as its universally used in different carb kits
 
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So I must admit I didn't read the instructions that came w/ the kit and I wound up using the wrong gasket between the throttle body and intake.....I will remove and replace. The instructions did not say anything about the washer under the seat, I did install a float w/o the washer and the float "fits" much better......so when I remove the carbs to install the correct gasket I will remove the bowl, remove the float, remove the washer and re-install the float w/o the washer.....and then re-install ALL the carbs correctly put together. Unfortunately I don't think this will change the performance much....not in the water.
 
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The kit came w/ 3 gaskets: (2) black different shapes and (1) brown thicker material. The instructions said to use the brown gasket for my carb number, I usaed the black one.
 
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