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Author Topic:   1982 Johnson 60-HP Gear Ratio

sternorama posted 05-17-2007 04:07 PM ET (US)
Please tell me what the gear ratio is on the lower unit of the 1982 Johnson 60-HP two-cylinder, two-stroke outboard motor. I would like to use the nifty JIM prop calculator. Thank you.
Also, what is the maximum RPM for this motor? Thanks again.
Lil Whaler Lover posted 05-17-2007 06:11 PM ET (US)
Gear ratio: 12/29 or .414
Maximum RPM 6000
sternorama posted 05-17-2007 06:17 PM ET (US)
Thank you. The 6000 is on the high side in comparison to the typical 5500. Do you know why? Just curious. Thanks again!
jimh posted 05-17-2007 08:03 PM ET (US)
If the gear ratio is 29:12 you would enter it as 2.42:1 when using the propeller calculator. Or, in other words, it takes 2.42 turns of the drive shaft to produce one turn of the propeller shaft.
Lil Whaler Lover posted 05-17-2007 09:02 PM ET (US)
Your 60 horsepower 2 cylinder was in reality a "tweaked" 50 horsepower engine. It had the same displacement, but simply put, its larger carbs could push more fuel and air through the engine at a high rpm generating more horsepower. The same block was also used for a 40 horsepower engine.
Your 60 hp engine was rated at 60hp @ 5,500 RPM with a maximum rpm rating of 6,000.
sternorama posted 05-18-2007 12:34 PM ET (US)
Thanks for the interesting facts on the outboard. It really is a nice motor-not too loud! I've never seen another. And thanks for the tip on the ratio for the calculator... once I predicted 168mph I figured I needed to use the reciprocal ; )
If anyone cares to continue this... in regards to estimating a slip factor I am interested in what you would expect to see. I am running a 13" pitch OEM aluminum prop with some cupping on a 1968 16'7" hull with all the railing, and an aftermarket stand-up center "consul" (sorry-could help but inject a little humor here), 2x12 gallon Tempo gas tanks in the stern, and a 15hp kicker on the transom. Add a small drag for transom mounted bait pump (I angled its mounting back, but I should probably angle it back a little more).
Using a range of 13.75"-14" for pitch, and a max speed of 29.8mph(gps), I get a range of slip from 7.7%-9.3% (ref: 6000rpm, 2.42 ratio)
Any similar data (for a slightly underpowered 16') would be interesting. Thanks again-G
Slow boat, I know, but she performs well this way for "offshore" with live bait tank and heavy crew. I have a 15" too that couldn't handle the heavy loading. One of these days I'll put that one back on and go for a solo speed run for more data!

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Author	Topic: 1982 Johnson 60-HP Gear Ratio
sternorama	posted 05-17-2007 04:07 PM ET (US) Please tell me what the gear ratio is on the lower unit of the 1982 Johnson 60-HP two-cylinder, two-stroke outboard motor. I would like to use the nifty JIM prop calculator. Thank you. Also, what is the maximum RPM for this motor? Thanks again.
Lil Whaler Lover	posted 05-17-2007 06:11 PM ET (US) Gear ratio: 12/29 or .414 Maximum RPM 6000
sternorama	posted 05-17-2007 06:17 PM ET (US) Thank you. The 6000 is on the high side in comparison to the typical 5500. Do you know why? Just curious. Thanks again!
jimh	posted 05-17-2007 08:03 PM ET (US) If the gear ratio is 29:12 you would enter it as 2.42:1 when using the propeller calculator. Or, in other words, it takes 2.42 turns of the drive shaft to produce one turn of the propeller shaft.
Lil Whaler Lover	posted 05-17-2007 09:02 PM ET (US) Your 60 horsepower 2 cylinder was in reality a "tweaked" 50 horsepower engine. It had the same displacement, but simply put, its larger carbs could push more fuel and air through the engine at a high rpm generating more horsepower. The same block was also used for a 40 horsepower engine. Your 60 hp engine was rated at 60hp @ 5,500 RPM with a maximum rpm rating of 6,000.
sternorama	posted 05-18-2007 12:34 PM ET (US) Thanks for the interesting facts on the outboard. It really is a nice motor-not too loud! I've never seen another. And thanks for the tip on the ratio for the calculator... once I predicted 168mph I figured I needed to use the reciprocal ; ) If anyone cares to continue this... in regards to estimating a slip factor I am interested in what you would expect to see. I am running a 13" pitch OEM aluminum prop with some cupping on a 1968 16'7" hull with all the railing, and an aftermarket stand-up center "consul" (sorry-could help but inject a little humor here), 2x12 gallon Tempo gas tanks in the stern, and a 15hp kicker on the transom. Add a small drag for transom mounted bait pump (I angled its mounting back, but I should probably angle it back a little more). Using a range of 13.75"-14" for pitch, and a max speed of 29.8mph(gps), I get a range of slip from 7.7%-9.3% (ref: 6000rpm, 2.42 ratio) Any similar data (for a slightly underpowered 16') would be interesting. Thanks again-G Slow boat, I know, but she performs well this way for "offshore" with live bait tank and heavy crew. I have a 15" too that couldn't handle the heavy loading. One of these days I'll put that one back on and go for a solo speed run for more data!