Anybody know about Vacturi-500 carburator adjustments?

[champ20B]

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!!

[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

[champ20B]

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

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.

[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 . . .

[champ20B]

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 . . .

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.

[smittythewelder]

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.