mercury outboard carburetor body throttle shaft bushings

[sam am I]

Has anyone ever preformed or know of a/the procedure to bush worn out mercury outboard carburetor throttle shaft bodies? I have a 1992 V-175 carb'd with WMH-15's. They're (1-2-3) fairly sloppy, to a point of leaking air in I'm sure.

I don't see where in the schematic these carb's even have bushings....Hmmmm. I have the motor tore down and want to go back as close to spec as possible.

Had an old quadrajet that leaked like a pig with roughly the same amount of slop, figure, it's time for these.

Thanks in advance,

 

[wired247]

Re: mercury outboard carburetor body throttle shaft bushings

Ive never seen a boat carburetor that needed bushings. If you figure a boat carb doesnt get much more than 1000 hours of use which would correspond to 50K miles in a car . In a boat you dont get the constant up and down throttle use like you do in a car and you dont have much of anything for a return spring which also wears on the shaft and bore. Boat carbs got to hell in the fuel bowl with old gas sitting for months at a time gumming up jets. Not saying your interpretation of the throttle shafts is wrong. Just saying Ive never seen a boat carb worn out like that.

 

[sam am I]

Re: mercury outboard carburetor body throttle shaft bushings

Ive never seen a boat carburetor that needed bushings. If you figure a boat carb doesnt get much more than 1000 hours of use which would correspond to 50K miles in a car . In a boat you dont get the constant up and down throttle use like you do in a car and you dont have much of anything for a return spring which also wears on the shaft and bore. Boat carbs got to hell in the fuel bowl with old gas sitting for months at a time gumming up jets. Not saying your interpretation of the throttle shafts is wrong. Just saying Ive never seen a boat carb worn out like that.

Well perhaps the play(very evident in a radial motion) that's there, was the "acceptable" tolerance from the factory? All three appear to have roughly the same radial slop. I have no spec or new carb. to compare too. However, with the play that exists, it has to leak, no doubt. That quadrajet i referred to earlier and as I recall, I was able to increase the engines RPM's by simply lifting (not twisting) the throttle, basically, it was significant enough of a vacuum leak, I could begin to lean the engine out over the idle mixture setting just by lifting it.

I didn't put more than an average amount of hours or work on the engine but, wondering now about "leaning" out conditions and vacuum leaks. I tore the engine down (just pulled the piston two days ago) due to having little to no leak down on a cylinder. Once inside, I have scuffing in 3 or 4 (one of which of course, is the bad leak down) cylinders. The motor has NEVER over heated or ever ran low on lube. Always used TCW-2/3 and 91/92 octanes. I would hazard a guess here, if a guy, in theory, is leaning a two stroker out with clean air (un-oiled fuel mixed air) vacuum leaks, he could, in theory, create a poor/er lube situation? But at what level leak would this have to be I wonder.

Again, not having a reference/spec, taking a mic reading could just be a moot point. I'd guess the things are moving 0.020" ( I will measure tomorrow). The butterflies are sort of hitting/sitting/catching the bore weird too btw when i move the shaft in this radial motion at the same time i'm opening them in a normal rotation as well. I think the butterflies have wore small seats over time and i'm able to move them in and out of the seats with radial movements.

It's tore down, so can't use the spray/fuel detect method to confirm but, that's the path I think i'm going to be on .........I might just re-bush them, not quite sure now.

 

[sam am I]

Re: mercury outboard carburetor body throttle shaft bushings

Well perhaps the play(very evident in a lateral motion) that's there, was the "acceptable" tolerance from the factory? All three appear to have roughly the same lateral slop. I have no spec or new carb. to compare too. However, with the play that exists, it has to leak, no doubt. That quadrajet i referred to earlier and as I recall, I was able to increase the engines RPM's by simply lifting (not twisting) the throttle, basically, it was significant enough of a vacuum leak, I could begin to lean the engine out over the idle mixture setting just by lifting it.

I didn't put more than an average amount of hours or work on the engine but, wondering now about "leaning" out conditions and vacuum leaks. I tore the engine down (just pulled the piston two days ago) due to having little to no leak down on a cylinder. Once inside, I have scuffing in 3 or 4 (one of which of course, is the bad leak down) cylinders. The motor has NEVER over heated or ever ran low on lube. Always used TCW-2/3 and 91/92 octanes. I would hazard a guess here, if a guy, in theory, is leaning a two stroker out with clean air (un-oiled fuel mixed air) vacuum leaks, he could, in theory, create a poor/er lube situation? But at what level leak would this have to be I wonder.

Again, not having a reference/spec, taking a mic reading could just be a moot point. I'd guess the things are moving 0.020" ( I will measure tomorrow). The butterflies are sort of hitting/sitting/catching the bore weird too btw when i move the shaft in this laterally motion at the same time i'm opening them in a normal rotation as well. I think the butterflies have wore small seats over time and i'm able to move them in and out of the seats with laterally movements.

It's tore down, so can't use the spray/fuel detect method to confirm but, that's the path I think i'm going to be on .........I might just re-bush them, not quite sure now.

The movement is close to 0.026". This is not good IMO, if I can see light through this, which I can, some portion of fresh air is getting in around these shafts now. Enough to effect the engine I presume in one way or another.

My thought here is, is this/my case an isolated case? I never drove this thing hard, just normal use.

And as the schematic indicated, the bodies have no bushing And why no bushings? Wow, steel shaft(Nickle plated Brass?), dry rotating in aluminum? Did they think the 2 cycle oil would wick into this? Hmmm, I can't image this lasting too long under very little use let alone normal, geeesh merc!!! really? really?


Well with no replacements parts and only other used parts out there with the same issues I assume, I think I can mill the shafts down to 0.265" (0.275" stock it appears) as I see about 0.269" worst case, oversize the bodies guide holes and press in some high quality permanent lubed bushings.

 

[Dukedog]

Re: mercury outboard carburetor body throttle shaft bushings

Never had a problem with 'em (wh or wmh) myself but then again, never had a reason ta check 'em that close either...............

 

[wired247]

Re: mercury outboard carburetor body throttle shaft bushings

I dont think its that big of a problem. They dont work the same way at idle as automotive carbs do. The throttles are completely closed at idle unlike the typical automotive carb that relies on the throttle plates to set idle and even if they did leak a bit through the throttle shafts you would just adjust the idle mixture screw and idle timing to compensate until you had a good off idle transition.

 

[sam am I]

Re: mercury outboard carburetor body throttle shaft bushings

I dont think its that big of a problem. They dont work the same way at idle as automotive carbs do. The throttles are completely closed at idle unlike the typical automotive carb that relies on the throttle plates to set idle and even if they did leak a bit through the throttle shafts you would just adjust the idle mixture screw and idle timing to compensate until you had a good off idle transition.

Agreed, not a HUGE problem per-se. True about the car but, merc uses a hole/s though in the valve to achieve what some cars do by setting a solid valve slightly open for a fixed amount of fresh air with a idle set screw. Same gig all in all though right? Allow some fresh air in, adjust the mixture screws for proper air/fuel ratio....

Primarily any issues would/are showing up at idles and yes, it can (maybe, see below) be adjusted out if you want to chase after it.


I guess how I view it is the fresh air hole in the merc valves are 0.160" in diameter, which gives an area of 0.02" for fresh air to move through. The worn shaft diameter is around 0.269" or an area of 0.0568". The bore for the shaft has worn open diameter to 0.282" or an area of 0.0625". Subtract the two areas gives the area of the air gap created by the wear 0.0625" - 0.0568" = 0.0056". 0.0056"/0.02" = 0.28 or 28% and presumably growing. I'm not sure the other systems are designed/able to span out to make that much up, maybe, i'm not sure. I assume it will just be getting worse and I'd be chasing after it.......you could be right though about making up for it but, I think i'll just go back with some sealed bearings and be done with it and run on the marks.

 

[Dukedog]

Re: mercury outboard carburetor body throttle shaft bushings

Your not "Schaffer" in disguise are ya?

 

[wired247]

Re: mercury outboard carburetor body throttle shaft bushings

Still think you are looking for problems where there are none. What you are doing will tighten up the throttle shaft seal which means that MAYBE you will get to close the idle mixture screws 1/8 of a turn and you can back off on the idle timing by 1 degree when you are done. It will still run the same. Outboards, at least late mercury V6's, are engineered so that the user can adjust the idle with timing and mixture to tune out wear problems in the carburetors.

 

[sam am I]

Re: mercury outboard carburetor body throttle shaft bushings

Your not "Schaffer" in disguise are ya?

last time I checked, I wasn't.

 

[sam am I]

Re: mercury outboard carburetor body throttle shaft bushings

Still think you are looking for problems where there are none. What you are doing will tighten up the throttle shaft seal which means that MAYBE you will get to close the idle mixture screws 1/8 of a turn and you can back off on the idle timing by 1 degree when you are done. It will still run the same. Outboards, at least late mercury V6's, are engineered so that the user can adjust the idle with timing and mixture to tune out wear problems in the carburetors.

Perhaps, but the shaft/s is worn down, starting to bind, has "uncontrolled air introduced through worn throttle shaft to bore interfaces. Over time, these two wear related problems interact to cause tuning issues which are corrected by remanufacturing" and "Throttle shafts that are stated to be "freely rotating with no play" may be a matter of opinion. A few thousandths of radial shaft clearance WILL cause tuning issues." and not going to stop as I see it. It's tore down, might as well get it stopped before it gets worse.

Source... http://www.performanceoriented.com/technical.htm

 

[wired247]

Re: mercury outboard carburetor body throttle shaft bushings

Ive got a set of WMH-14's from an XR-6 I was going to throw out. The have good throttle shafts. Venturi bore is too small to be useful for me but the shafts are good and I believe the plates are the same as the -15's. Yours for the cost of the postage.

 

[sam am I]

Re: mercury outboard carburetor body throttle shaft bushings

Sold, PM me your address, I'll send you a pre-paid bubble envelope and you can just pop the shafts/plates in.

Thank you, and the GF says "send him some of her homemade huckleberry jam too because he got you to stop whining"........damn girls

 

[wired247]

Re: mercury outboard carburetor body throttle shaft bushings

PM sent. Huckleberries?

Where you at?

 

[sam am I]

Re: mercury outboard carburetor body throttle shaft bushings

Coeur d'alene ID......Picked them this summer up North a tad in Griz country, North of Bonners, close to Canadian boarder, Kaniksu National Forest.

 

[wired247]

Re: mercury outboard carburetor body throttle shaft bushings

Yeah, We get them from Mt Adams Indian Heaven area.

 

[gm280]

Re: mercury outboard carburetor body throttle shaft bushings

Glad to see you have it all covered now. After looking at the last set of pictures, number three in that set looks awful to say the least. I had a similar situation with a kohler carb on my old lawn mower this pass year. So I made a new one from a brass rod blank and drill press and files. It fit and works perfect.

 

[sam am I]

Re: mercury outboard carburetor body throttle shaft bushings

Those last 3 pic's were just various pic's from the web of where shaft wear can get worn too :facepalm:....., I don't think the merc's could/have ever get as bad as that last one but.............

 

[sam am I]

Re: mercury outboard carburetor body throttle shaft bushings

Found myself in the garage (too full to do anything else), started tinkering with these worn carb shafts etc.

Had a thought of what my merc guru mech (guy eats, breathes, lives merc's, I swear) go to guy said to me a few weeks back when I reported to him i had a hole (#4) with no leak down to speak but around 90 psi and that after opening it up, saw scuffing........he said "something wrong with the carb I bet".

So of course with that and this thread, it's obvious I have been looking real close at carb's lately to try to find something and MAYBE I have.

The motor's #2, #4, #6 holes are the worse of the bunch(#1,#3, #5 all look pretty darn good) #4 though, being the dead duck as far as leak down.......Well perhaps again, i'm looking waaaaaaay too deeply for something but, cylinders #2, #4, #6 happen to be carb. throats on the throttle linkage side AND, the throttle linkage side of the carbs happen to be where the largest wear(assumed by the gap calculations above to be highest air leakage side) in the shafts are........

The pic up in post #4 is my WMH 15-2 carb.(i seriously didn't realize I had grabbed 15-2 to tear down until tonight) and that close up in post #4 is of the leakage side of that carb's throttle shaft..........

The other day when reading and looking around for info regarding carb. shaft wear and fixes etc, i saw this pic




Then I just took a pic of my 15-2's (sharpie marks I added)



The valve on the right is cylinder #4's valve and is, again, on the linkage side (now pretty much confirmed highest leakage point due to this second source)..........Then glancing at 15-1 and 15-3 right throat valves (cylinders #2 and #6), they're darker then the left side's as well. #2's resembling this one pictured above.

Cylinder #2 of the other 5 holes did have about 50%, and of course has the second worse scuffing I can see. AND, that cylinder's carb (15-1) is yes, the other carb with a pretty high degree of sloppy shaft wear.

15-3 is the least worn of the carb.

I will measure the actual wear on the shaft tomorrow.

Coincidences? or something far more sinister, like creepy aliens? ahhhhhh heck, I maybe just ate too much, nevermind

I'm going to re-bush these POS's in a few days, I'll post some pic's/info as things come about.

 

[Dukedog]

Re: mercury outboard carburetor body throttle shaft bushings

Had a thought of what my merc guru mech (guy eats, breathes, lives merc's, I swear) go to guy said to me a few weeks back when I reported to him i had a hole (#4) with no leak down to speak but around 90 psi and that after opening it up, saw scuffing........he said "something wrong with the carb I bet".

Courious 'bout this. We do comp and leak down on fresh motors before a reed plate is even installed and see very, very, (if any at all) little difference in tha numbers????