New Carb Parts for a 70 Johnson?

Ok so i have a 1998 J70 TLEC. My question, out of some fun curiosity. My engine runs good. I did a bunch of work on it myself. Thanks to this forum. I had a couple of problems and they have been fixed. How much better would a carb(3) be if you replaced the covers, needle(3) and gas and air orifices? My common sence tells me that 100’s of gallons of fuel had to of gone by over the needles of the 3 carbs, does anyone beside me think that these parts may have worn over the last 20 years? Were talking roughly about $75 for each carb. Do you think it would make any noticeable difference? A slow speed adjustment needle alone costs $40. Just curious.

My opinion: The parts you mention are not normal wear items.

Well i put a set of Boyesens in Definitely made a difference. Maybe not normal wear but over 20 yrs? Their has to be some. Wouldn’t it make the carbs, almost new?

Just thinking is speculation pure about it.... like the thoughts through your mind running about that blonde so curvaceous on the street corner waiting Hmmmm?

Just do it, hesitate not for the dollars you have and miss you will not, then see the results we will... and may the force be with you. :rolleyes:

Well lol a few of us Have Had that blonde, not a disappointment for some. I was just wondering if it has been done, on the carb subject of course. You see plenty of used carbs for sale on the internet. Some single, some as a set. The main reason on why i had this thought. Some where along the life of my carbs, some one before me tighten the needle on the #1 carb down so tight it actually put a grove in it. I sanded it lightly down to even it off a little but it made me think about the mechanical aspect of how it works. The covers on those carbs are made from plastic they dont leak, but must provide a service to the performance. Again this was a question of curiosity. Im sure the new needles they sell, as well as other parts are for ones lost, not as a replacement for wear. Would it not be harder to sync the carbs if those slow speed needles worn? Idk, thats why i put this out there.

Yeah... the purpose of the post I figured as much... a curiosity thing.

The adjustable needle valve becoming worn... yes, some do turn them in hard and that causes damage (grooves). However a lot of the carburetors (yours) have a very small nylon bearing on the front shoulder of the valve and failure to replace that nylon bearing allows the forward end of that brass valve to vibrate which causes that same grooving problem.

For what it's worth... I use a small 4-41 tap to remove the old bearing. Installing is simply a matter of slipping it on the needle valve, then turning the NV in to seat the bearing. The 4-41 tap is just right to grab the bearing without penetrating it which leaves the aluminum intact.

Pertaining to a existing groove and the removal thereof... a drill press, or a drill mounted in a vice turning that damaged NV, then holding a file at the proper angle against the taper... that usually saves the valve for another day so to speak.

Using a NV with a groove on its taper.... it is impossible to set the idle mixture. The synchronization is more a mechanical thing that could still be obtained, but still, the engine would not be running as it should.

Unfortunately the cost of replacing all needle valves, jets, whatever, new... yeah, that gets a little pricey.

Thanks Joe,as always. The voice of knowledge. I noticed in the carb rebuild kits that bearing. I thought thats what the spring was for on that intermediate screw, seems its a little bit more than that. Maybe thats why guys dont go through the trouble. By any chance would you happen to know the vacuum lines ID for that motor. Their unavailable, but could i put newer ones on there. The ones i got are so broken down, im surprise they are working. Its a heck of a small id.

I must admit that I somehow overlooked the year of your engine (1998) as I was more interested in your explanation of the worn groove of an adjustable brass NV. I retired in 1991 and frankly I don't know if your engine has use of that small clear (or white) nylon bearing that's incorporated with the brass adjustable NV or not, but whatthehell... it's worth knowing anyhow.

Vacuum lines?... Might you be speaking of the extremely small ID Fuel Primer Hoses? If so, the ID of that hose is damn small... 0.0575 and is normally cut to size from a 25' roll, part #327229................ (see following paragraph)

From this point (directly above) it gets very confusing as this number and another earlier one both supersede to #0772568 which list the ID as 1/16" and selling for $2.47... Neither OMC nor Bombardier is going to sell a 25' roll of this hose for $2.47... so I consider this supersede entry a boo boo and am ignoring it.

Anyhow... If this is the hose that you're speaking of, and if you have a problem locating it (should be available on this site), PM myself and let me know how much of it you need as I have quite a bit of it left in my remaining stock.

I see that #0772568 ID 1/16" is available here, by the foot roughly $3.00 per foot. Apparently the $2.47 I quoted is also per foot although it doesn't state that in the book.

Thanks Joe thats my fault. I should have remembered in another conversation we hard some time ago. I should have reminded you. Since were on that vacuum line subject. What symptoms would a running motor have with a restricted or collapsed vacuum line? I replaced all the 5/32 carb fuel lines. From O’Rilleys auto. My boat store didnt even have them.

Post pictures of these " vacuum lines " as I do not believe there are any on this motor.

From the electric choke of my outboard all 3 from there to each of the carbs top in a nipple. Opposite of where they go in there is a fixed air orifice.

There is a fuel line 5/32 going to the bottom of each carb. Im assuming they are vacuum lines. I have a service manual for that engine. Doesnt say anything. The same goes for the relays of my ptt, no mention of them. Its weird that they are not mentioned

The 3 lines on the electric primer are FUEL lines.-------All the lines going to the carburetors are FUEL lines !-----Why are you assuming they are VACUUM lines ?-----If motor runs well then do not try to improve on it.-----You might post results of a compression test and keep that for future reference.

I obviously was wrong. Got behind an outboard for the first time in my life, a whole 6 months young. Lol I assumed that because of the fixed air orifice opposites of it. Now that it was explained to me I understand where that electric primer comes into work. Thanks and at any, extremely hard to get those. So any air coming in is strictly down just the carb throat? Are those fuel lines from the primer only for cold starting? Or fogging oil, carb cleaner etc?

If it has the shreader valve installed you can use it to inject various motor tune-up / tonic items.-----The primer is only for cold starting.-----You push the key in and hold it in while cranking it over.

Yes it does. I decarbed the motor with it. Thanks for setting me explaining those fuel lines to me. Crazy small id on them

And they are a small ID because they do not need to carry a lot of fuel or other product !!-----When you understand how things work the trouble shooting will be so much easier.

I appreciate the straight forward response and your feedback. The motor is 20 yrs old, it has a good power head with 140 comp on all 3. So just trying to take care of the Obvious. Other than that im taking it on as it comes. I know its easy to open a can of worms, where there shouldn’t be a need to.