Gear ratios on 1950's Johnsons.

[55Crestliner]

I have a '55 25 horse Johnson, and I'm thinking of buying a '58 35 horse Johnson. My question is about the gear ratios. Are they different?If a 14 inch pitch prop is all I can get, and it's already reving somewhat high on the 25 horse, what will a 35 horse engine do on my boat? Will it be way over-revved? What to do, what to do, I'm sure one of you will know... Link to my post about prop pitch

[Chinewalker]

Hi 55C, Pretty much all of the Big Twin models ran the 12:21 ratio, so there will be no change. 14-inches is a pretty tall prop, so I don't think a 35 will spin too freely with it. How high is your 25 revving? Have you tached it out? They're generally rated at about 4500 revs, but taking them up to 5000 usually isn't a problem. Don't take them any higher than that - the flywheels are awfully heavy on those little crankshafts. There's a reason why they had to go to the beefier crank on the 40s...- Scott

[55Crestliner]

The 14 is doing about 4330. I bought a 2 blade bronze, (the kind with a rubber hub, so hopefully not damaging to lower end), it's supposed to be a 14.5, but it's turning about the same RPM, same boat speed.The 35 looks like a good deal, I wanted to hit 30mph, and I like the color better than the green '55. I just don't know if it's worth the time and effort (and $) if it's not going to do anything for me but overrev.The listing I found for the '55 was 4000rpm, and the 35's I have listed as 4500. SO, I guess it would be an improvement, and within specs.Thanks for the gear ratio info. btw, just as a side note, the 25 horse is giving me better mileage than the 18 did. I went all the way around Mercer Island in Lake Washington on one 4 gallon tank with the 25, but I had to add my reserve fuel 3/4 way around with the 18.

[Chinewalker]

I'll bet the 18 was running full bore all the way while the 25 was able to throttle back a bit - big savings there...I've run a 2-blade bronze on a 30 Johnson and they work well. If it has a bit of a cup to it you can even jack them upwards a bit to reduce drag. Even though the water intake is in the exhaust outlet the prop blades through a ton of water in there when underway, so having the water intake out of the water a little isn't much of an issue. I've run my short-shaft 30 (nominally a 15-inch motor) at almost 19-inches on a racing hull, so you can go pretty high.- Scott

[55Crestliner]

That's a great picture, very cool. Those pictures almost always have a Merc hanging on the back.Judging by the cars in the background, and by a picture I saw of you on your site, you don't seem "aged" enough for that to be you in this picture. Sounds like cupping is in order for my prop, it's mounted pretty high, and I get some ventilation on turns when trimmed out.

[Chinewalker]

You are correct. That would be my Dad. That boat is currently in the Antique Boat Museum (www.abm.org) collection and will soon be on display in their new outboard exhibit. It's a 1959 Sid-Craft Hornet, 13-foot , with a '56 Johnson 30 on it. I've run a twin to it, set-up the same way. Quite a handful, and a very fun ride... It was raced in what they called "36 Class". It used motors that checked in around 36-cubic inches on 13 foot utility racers. Class was popular for a number of years into the 1970s before it died out.- Scott

[55Crestliner]

Thanks for the story, I never get tired of hearing of that stuff. What did they use for bottom ends on the Johnsons? Did they make a race version? Has anyone ever tried to "add on" to the bottom end with sheet metal or something to make it flow thru the water better?

[Chinewalker]

It was a bone stock lower unit - full gearshift and all. Some guys tried to skirt the rules by removing the reverse gear and welding the forward gear to the shaft (to reduce friction), but that was about the only mod I've heard of. There was a gearfoot made by Vrooman-Cornaire in Watertown, NY that was a direct drive, more streamlined gearfoot. It is VERY rare, and those that are out there are generally chewed up pretty good. Seems the off-the-shelf gears they used were not case hardened and wore down fairly quickly. We have one of these units, but the thrust bearing is a mess. It had loose ball bearings riding on an aluminum race. Very peculiar. Not sure if it came that way or if someone tried to "fix" it at some point. The V-C unit only fit the '51 to '54 Big Twins (6-bolt), although rumour has it that some were made for the '55 and up (7-bolt) units. I have not seen one. I have only seen three of the V-C units in the years I've been collecting. The story goes the Vrooman and Cornaire had a falling out and one of them sold the remaining inventory for scrap. A friend of mine actually found the carved wooden plug used to make the castings in an old foundry in Watertown about 10 years ago. Another friend who owns one of the units allowed me to disassemble his to compare it to mine. Quite different, although it still didn't have a proper thrust bearing. I may attempt to re-engineer mine at some point and try it out - someday. Here's a couple pics of our V-C unit on a '54 Johnson 25 along with the wooden plug... - Scott

[55Crestliner]

Very cool. Looks quite speedy - except for the thick Anti-ventilation plate, but I imagine that would be out of the water most of the time.