Anybody know about Vacturi-500 carburator adjustments?

I have recently finished a complete mechanical restoration on a nice complete PO-15 (22 HP) Johnson....the big iron twin beast! I acquired it and a little 1956 Johnson 7.5 for later restoration from a good friend of mine. The old PO-15 is a fishing model, but somebody long ago got the bright idea of putting on a racing carb (Vacturi-500). This carb is a monster. It has about a 2" throat and about a 1-3/4" venturi from the looks of it. I did the grease to hypoid oil conversion on the lower unit with all new sectional gaskets (basically, move the end prop shaft bushing just under 1/4" inward and press in a 1-1/8"OD-7/8" ID seal). These engines never had seals of any kind. The heavy waterproof grease acted as such (lousy idea, but pretty much worked). The drive shaft had no worries as it is completely encased within the shaft mid/tube where nothing could get in from outside. I took her all apart and checked it all out. I cleaned out the two separate cooling systems (prop thrust feed type) in both the powerhead and exhaust. They feed from a vent behind the prop and are totally separate with separate outlets (good design! Better cooling). I made all new gaskets including head gaskets.......

Making head gaskets from reinforced material (metal embedded), outside can be cut with heavy shears, holes cut with ground old sharpened sockets of size with hammer, and cylinder hole is carefully cut with a hammer and narrow sharp flat shaped chisel along the mark...works nicely upon a flat anvil/vise. Smooth cut!!

I soldered some nice Belden plug wires on the coil as well. I put on fresh Blue Crown cool range spark plugs I got with the motor (cant get those anymore!). I gapped the point to .020 and put on a dab of lithium to keep it lubed.

The pistons, rings and cylinders are perfecto!!! Very nice internals. I oiled it all up inside upon reassembly and "good gosh" the compression is high!!!
Buddy, you'd better eat them Wheaties to crank this old Gas-Punk beast! And that's with one cylinder working. The other has a relief valve, and yeah, you would need it. It would take a truck to pull it over with both cylinders pressing....I was told it has high compression "soup up" heads. Oh well!

Another neat thing is the automated idle relief valve (great idea!). The way it works is that the piston valve drops the let off back pressure from exhaust. When the engine starts up, the water cooling pressure pushes the valve piston up to close the exhaust relief.

Well amidst all this jabber, I am ready to take it fishing all day! What I would like to know is what the idle and high-speed settings were initially for the Vac-500 carburetor. They were used on Hubbel and Johnson PR racers I think? Thanks!!

There are a couple versions of the Vacturi. There is a large needle and small needle version. Almost all racers use the large needle version which is what was used in the F, 4-60 motor.

On a PR most of the large needle carbs run at 1 1/2 turns for the high speed needle. The low speed needle, I only have open a tad as I don't idle a PR or Service C.

Keep in mind, the race motors run on methanol so gas and oil I am sure will be different.

Tim

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Originally Posted by Tim Weber

There are a couple versions of the Vacturi. There is a large needle and small needle version. Almost all racers use the large needle version which is what was used in the F, 4-60 motor.

On a PR most of the large needle carbs run at 1 1/2 turns for the high speed needle. The low speed needle, I only have open a tad as I don't idle a PR or Service C.

Keep in mind, the race motors run on methanol so gas and oil I am sure will be different.

Tim

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Thanks Tim! I appreciate this info. I haven't tried to crank it up yet, but I hope it is a stock (gasoline) version of this carb. If it isn't, I might not get it to run so good. Mine has the old 90 degree up turning inlet piece with the square raised lid on top that is mounted over the choke. It is also the same color (green) as my motor. The carb adaptor plate looks homemade from 3/8" thick metal piece.

A carb with a 2" throat seems pretty big to work well on a motor for trolling, doesn't it? As I recall, some of the guys in the Sixties who were adapting Vacturis to use on alky engines other than C Service would get on their lathes and turn sleeves to get the Vacturi bore down to the diameter they wanted . . .

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Originally Posted by smittythewelder

A carb with a 2" throat seems pretty big to work well on a motor for trolling, doesn't it? As I recall, some of the guys in the Sixties who were adapting Vacturis to use on alky engines other than C Service would get on their lathes and turn sleeves to get the Vacturi bore down to the diameter they wanted . . .

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It definitely would seem a bit much carb for practical use by looking at it. I haven't had a chance to try it out yet though. I found out by searching around that this carb is a Vacturi (36D10) model, and was used on the PR50 Johnson-16hp racer from 1930. This carb dates way back. Being that, it might work I hope.

The unique thing about this motor is that the heads don't have the threaded holes for spark plug covers. It also has the short tiller handle with the throttle in the middle of it, not the longer one on later 22hp models. I have a standard 3 blade Michigan 12"x12" on it now and I have an optional 2-blade Stannus race prop that fits it and functions perfectly with the water vents. That prop is a 10"x15.5" and looks almost like a cleaver. The prop shaft and shear-pin are a direct match on it. I always wondered what that prop was for, and by coincidence, I found out.

I tried to find numbers to identify it for sure, but cant find any. The numbers that are supposed to be on the flywheel top are totally faded off. The only indication I have on this motor is its "Johnson -correct green color", but someone could have painted it long ago. It looks old and aged cosmetically, just how I like em!

For all I know, this could be an old PO37 or 38 from the late 1930s... But so far, it is mechanically one of the very best condition engines I ever came across. Surely a good runner to be. I really enjoyed working on it. It was a very smooth going project without much challenge at all.

Well, Champ, I phoned Jim Hallum, now in his early eighties, who besides being a mechanical engineer and a career marina mechanic built all of Gerry Walin's record-setting A and B Anzanis in the '60s and '70s, all of which had Vacturis, alongside which he added various numbers of little Tillotson pumper carbs. He said he sleeved the bores of all the Vacturis, smaller for A's, bigger for B's. The sleeves had straight throats, no added venturi. Since this was a phone call, and I had no example to look at, I can only say that Jim recalls that there were one or two discharge tubes (of some sort) that had to protrude a little past the I.D. of the sleeve to draw well. There also are some little idle passages that are uncovered by the edge of the butterfly in the stock carb; obviously, when you sleeve the bore, you have to make a new butterfly for the new bore size, but you also need to make holes that angle through the sleeve to come out at the right place viz. the trailing edge of the new butterfly.

Jim is skeptical of how well a Vacturi of any bore would work for trolling with your opposed twin. The vertical butterfly shaft could make one cylinder run lean or rich compared to the other at small throttle openings. He suggests you might have better luck with one of the horizontal-shaft carbs that also came on many older OMC engines.

UPDATE!! I took it out for a run today!! Here's the tale of the tape......

It started right up, by the second pull...I had to lean it out a bit to get it smooth, but it ran pretty well. It does idle pretty good. The only thing is that because of having a smaller jon boat (14' length, 44"beam, 34" bottom) which is a lot like a big flat bottom canoe, It wants to get going and fast. It gets to really moving at a fast cruise 20-25mph, when the timing is about 1/2 way from middle to full advance position. The carb is only cracked open about 1/4" gap on each side of the throttle plate. It just really gets to going quick and to run it full throttle would probably be way more than that boat can handle. My old super-10 Merc wizard and Mark-20 Merc can run full throttle safely though fast. But this 22hp Johnson is far more motor than the 20cid Merc ever was. I was fooled by old advertisements and/or write ups by historians to believe that the Merc could equal it as was claimed and supposedly tested long ago. But today, I found out different for myself. This old iron is a very powerful and fast outboard without the high RPM. Just real raw power and quite reliable. I shut it off and restarted it every time at one pull every time. It is a loud machine though, like a WW1 air-plane engine!! And its just cool....

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Originally Posted by BRIAN HENDRICK

Vacturi carbs were OEM on many Ps pre and post war, not race motors, gasser fishing engines.
This article is from a early issue of Antique Outboarder, maybe by Bill Salisbury in VA ?
The Richard Hawie refered to is RCs father.
Vacturi made a CV carb for the S & P motors in the early '30s, with a built in fuel pump.


Vacturi AO-500 Carburetor

Common complaints of fuel flooding over and spilling out the discharge tubes when the carb is full of fuel and engine not running, are most often caused by a float that is too heavy. Additionally, it can be caused by a float needle and seat not sealing when the float is all the way up.

Remove the float and weigh on balance scale with hairpin clip and screw removed. The float should weigh between 7.5 and 8.5 grams. 9.5 grams would be absolute limit. Over that, the float should be replaced.

Once replaced, the carb can be tested using a guide for the float pin in place of the carburetor top. Hold the float pin up while filling the bowl with mineral spirits. Fill so that liquid level is about even with top of float. Then let go of float pin carefully. Liquid should not leak out of bottom. Then, with suitable syringe, draw off excess liquid to the point where float pin still remains sealed and by removing just one or two drops more, the pin will drop, allowing leakage out of the bottom. Note where the liquid level was just before the leakage began.

With a newly made float that weighed 8.5 grams after coating with two coats of model airplane fuel proof dope, the fuel level was noted at ½” below the top of the bowl and this corresponded to ¼” below the top surface of the new float.

The new float was made to the following dimensions: diameter is 1.800” and thickness is 1.000”. Since it is very easy to sand cork, cutting down an oversized cork to this dimension is not difficult. I traced an outline on the new cork material and marked it with a marking pen and then band sawed to the rough shape. I also band sawed the height to a little more than the 1”, finishing up by sanding on a disc sander. The new hole for the float pin was drilled in the lathe using a 1/8” drill.

The proper size of the venturi insert is often a question. According to an article written by Richard A. Hawie in the October 1983 issue of The Outboarder, the following three sizes were made for the Vacturi and these sizes specified for the following engines:

1 ½” for Johnson S and V engines
1 5/8” for Johnson XR
1 ¾” for Johnson P engines

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Thanks for this info! My Vacturi carb is the exact one that came with the early PR-50 (Johnson "16" racer). It does have about a 1.75" venturi. Interestingly, it is working very well on my PO-37 or 38....(I have already determined that my 22hp is an earlier model, not the PO-15 ). It really does idle very well, and it is very strong at fast cruising. My engine seems not to need much advancement in timing (1/2 way between middle and full) and responds well to opening the carburator on up instead. It has adjusted on the low and high speed quite easily, around one turn on the high speed.

Off the subject, about the cooling system for anyone interested, this engine had what was called a pressure/vacuum system. Water was forced by propeller up through the power-head and supposedly pulled out by the prop in a loop. This idea is hilarious to me!! I cant help but laugh at many of the engineering ideas I have seen and still see! And I'm not even an engineer on paper, though I could easily take on the job of a mechanical engineer any day. I just instinctively see how things work and I use my mind very well and study what I see carefully.... But to get to the point, I simply disconnected from the return portion to allow the outlet tubes on top of the cylinders to simply release water outside so it can be monitored for safety of cooling. It still works very well even at a slow idle. If the vacuum side does do anything at all, it would make a great bailer system for the boat (just put in a fitting for a tube and make a heavy pick up screen to set in the boat like the Scott/McCulloch used to have)!

I have also made a "spring adjustable" synchronized throttle linkage, so that timing and throttle works together at proper ratio from the timing lever alone! It works beautifully. Heck, I will have this engine as practical as a much later model except for not having gearshift! I could fix that too, but I had rather keep it nostalgic.....

Hi friends! Well, I went for a long boat ride today and you wont believe what happened! One of the cylinders came loose! It did not cause any harm...but something I want to emphasize is that if anyone wants to restore one of these legendary Johnson (PO) outboards, always make sure you use a strong automotive quality spring/lock washer on everything!! These engines are like the Harley Davidson of the sea and they will vibrate apart in a New York minute!! I was able to correct this problem and I will go try for some Spanish Mackerel in the bay in a day or so.....Don't worry, I am persistent about rinsing and flushing sea water!!

Another thing I want to update about for any interested, is that the suction side of the cooling system actually works!!!! It is not really needed for the engine cooling though as I stated in an earlier post, and it doesn't do much at low speed either. At high speed, it really pulls and will work as a bailer for the boat. I will use a on/off valve though, so it wont siphen water in the boat when its parked at the beach. If you think about it, through prop exhausts on todays motors must actually create a pulling affect that helps to remove exhaust more aggressively based on this observation as well.