With all the new technology

[89retta]

When will a boat manufacturer make a automatic transmission ? This would sure take all the guess work out of selecting the right prop. And I'm sure they can do it . Would just come down to how much it would cost the consumer.

 

[tpenfield]

Would be a boat engine manufacturer, since boat manufacturers buy their engines.

Would be a nice idea . . . but I'm sure there are some challenges to it.

 

[QBhoy]

Would probably add weight and rule out a streamline outdrive application with the current technology ?
Would be nice though

 

[H20Rat]

Lots of cost, weight, complexity, and you STILL would have to pick a prop. Too much pitch and the transmission would help get you out of the hole, but your low speed handling and efficiency would suck. Too little pitch, and your drag losses from swinging a prop around very quickly would kill any gains.

A better solution, which is used on large boats/ships, is a adjustable pitch prop. There USED to be a system for small boats many years ago, never really caught on as it really didn't offer any benefit. Ported props are already automatic transmissions for a boat, and it costs next to nothing to drill a couple holes.

 

[89retta]

Been thinking and it wont add to much weight. Like I said with todays technology and ultra tough light weight metals They could make it fit within a sterndrive. And I don't see why you would still need to pick prop pitch. My truck still shifts the same with 22" tires as it did with 17" ones.

 

[mr 88]

IF it worked, it would of been done years ago ,especially with off shore fishing boats that have the size and room for any transmission you want to stick in there. I am no engineer but logic tells me that you have so much weight and drag that it would keep downshifting to " 1st gear " Imagine pulling a big boat and trailer UP a steep mountain road,there is no way its going to shift into overdrive or any other high gear without you keeping it constantly floored and then it will just keep hunting for the right gear and stay there.There is no "coasting" or loping along in a boat. Just throttle back when your on a high speed or any speed for that matter cruise and the boat comes to a stop in a very very short time. Now do that in a car,throw it in neutral ,and it goes quite a long distance. Like I said ,with off shore boats traveling 200 miles round trip if there was any way to increase fuel mileage, these guys would have them in there war wagons,and they have the money to do it. Basically your prop is your transmission with slip when taking off/shifting/ and bite as your up on a plane at a constant speed.

 

[Chigwalla]

Been thinking and it wont add to much weight. Like I said with todays technology and ultra tough light weight metals They could make it fit within a sterndrive. And I don't see why you would still need to pick prop pitch. My truck still shifts the same with 22" tires as it did with 17" ones.

Notice they don't generally make anything for boats out of "lightweight materials" ?
Besides, boats already have an automatic transmission: that's why you can rev the engine in gear at the dock

 

[89retta]

Notice they don't generally make anything for boats out of "lightweight materials" ?
Besides, boats already have an automatic transmission: that's why you can rev the engine in gear at the dock

​Revving the engine at the dock does not make it an automatic. All it has if forward , reverse and neutral.

 

[Chigwalla]

I said that with tongue firmly planted in cheek, but it actually does: when you increase the load, the slip increases...otherwise the hole shot would stall the engine.
How is that any different than playing with the stall speed of a torque converter ?
Try revving your car in gear in the driveway if it's an auto vs if it's a stick.

 

[Slow Ride]

I've heard all sorts of arguments and discussions on this subject over the years..... pros and cons. I remember the variable pitched props as mentioned above. I was told by an old timer that they didn't last long due to corrosion and were near impossible to keep balanced. Don't hold me to that, its second hand information shared over a Budweiser or two. But, here is my beef with this idea as it pertains to outboards. Even if you could get one in there, and you probably could as I think about the motorcycle world, how much would it add to the cost of a new engine? These days a new 250 outboard by any manufacturer is around 20k+- with gauges, steering, controls and a prop. Throw in an automatic transmission and you will need a second mortgage to get it to the dock! LOL

 

[tpenfield]

Although, prop slip is like a torque converter . . .

 

[roffey]

I believe they have automatic transmissions in drag boats and such. I bet it is a cost factor, who would be willing to pay for it? I suspect you would need extra power to keep the boat on speed and plane after the shift.

 

[Scott Danforth]

there are companies out there that make 2-speed center sections for the Volvo (IVSS stepdrive) the price wasnt bad, however the target drive was becoming obsolete when the drive was introduced. the shifting was not as smooth as it should be.

many jet boats have a 2-speed power glide between the motor and jet to allow the motor to come up to WOT instantaneous

also, if you look at prop curves, the prop slip itself is just like a torque converter like Ted mentioned. we would need a gear change section. a typical planetary setup would be ok, however a CVT trans would be better.

now we just added $4k to the cost of the parts the boat manufacturer just bolted into the boat. that $4k that the boat manufactuer spent is now $10k sold to the average boater to cover warranty, overhead, etc.

you still need to match the prop to the load of the motor

 

[H20Rat]

Been thinking and it wont add to much weight. Like I said with todays technology and ultra tough light weight metals They could make it fit within a sterndrive. And I don't see why you would still need to pick prop pitch. My truck still shifts the same with 22" tires as it did with 17" ones.

Your tires aren't trying to swim through a viscous fluid. The size of your tires actually does affect performance (both efficiency and performance), but it is small enough you don't realize it. Larger tires will almost always cause you to accelerate slower in a typical street vehicle, even if you swap rear end gear. Another way to put it, generally bigger tires = more rotating mass, much like a low pitch prop spinning fast has more drag than a high pitch swinging slower.

 

[H20Rat]

many jet boats have a 2-speed power glide between the motor and jet to allow the motor to come up to WOT instantaneous

Don't know if I'd say 'many'... I've owned various jets and have spent quite a bit of time in the jet community, 2 speed powerglide jets do exist but are almost unicorns. Jet pumps are different from props, the load on the engine doesn't vary based on speed. The boat could be tethered to a dock or flying down the river at 60 mph, the engine will hit the exact same rpm.

Tires and props are spinning things to be moved, jet pumps operate like hydraulic engine dyno brakes.

 

[JASinIL2006]

The guesswork involved in trying to select a prop is starting to sound pretty inexpensive compared to the alternative...