When will we see a CVT in a MC?

[vision]

When will we see a continuous variable transmission in a MC or other inboard? Anyone on the inside have any thoughts?

It would seem to be such a logical use of a CVT. If they can handle the torque of a large diesel in a tractor trailer, a boat should be nothing. Is it just development/manufacturing cost for a relatively small market that keeps then out of our boats?

Any gas pickups available with a CVTs?

[FrankSchwab]

What advantage do you think a CVT would give us?

[vision]

Originally Posted by FrankSchwab

What advantage do you think a CVT would give us?

With a continuous variable gear ratio, you could mimic having gears without the need to change gears and the rapid loss of momentum.

Once on plane the CVT could "gear up" giving you a better top end at lower RPMs, without sacrificing a good hole shot. Besides allowing the use of smaller motors and having better fuel economy, you could theoretically extend the life of your engine by allowing it to run at a lower average RPM.

[FrankSchwab]

Well, I'm not sure...

If I hit it hard from a dead stop, the engine spools up to 3-4000 RPM before the boat has significantly accelerated; this is just about the torque peak. There's no need to change transmission ratios here; with a constant prop pitch, raising the engine revs here won't help.

Properly propped, a boat shouldn't be able to hit the Rev limiter at WOT; changing transmission ratios here probably won't make the boat go any faster.

Many people who use significant ballast (wakeboarding or surfing) underprop the boat, to help in both the pullout and in keeping a steady speed. It's not clear how a transmission ratio change would help here.

I suppose you could upshift when cruising across the lake to reduce engine RPMS; but too many years on motorcycles haven't convinced me that lower RPMs are really that significant of a determiner of engine life.

Are there many multi-speed marine transmissions at all? I'd think that the gear change time would be so small compared to the inertia of any large ship or tug that, if there were an advantage, they'd be using them.

[kgrove]

It seems like the parallel to a CVT for boating would be a variable pitch prop, not a transmission.

[Tap]

This CVT topic has come up before. A search may be in order. The first consideration is additional weight in the boat. THe variable pitch prop would be the similar to that of Helicopter main blades. The concern here is that linkages to adjust pitch would either be external (bent by rushing water - not air0 or internal (making for a shaft that is twice the diameter of normal shaft size).

still it would be great to have one. Engine will maintain RPM and reduce wear and tear.

[Miss Rita]

I'm inclined to think that the water acts as a CVT. Think of it: when you punch it, the engine revs to ~3000 rpm. As the boat accelerates, and the prop hooks up, speed increases but the revs don't.

When I drive for my friend, I give it full throttle, set the revs at 3600 rpm, and it dials in the perfect speed (for him) of 34 mph.

Variable pitch props have been tossed around for I/O's for 20+ years. They're most useful if you have an underpowered boat. They're not very popular.

Mercury used to make a 2-speed transmission for sterndrives. I don't think it's been available for quite a long time; there must be a reason for that.

I wouldn't hold your breath for a CVT.

[Finnsdad]

mb sports has a 2 speed trans option

[3event]

Echoing notes above, MB Sports has offered the 2spd tranny for several years now, but it certainly hasnt taken the boating world by storm.

Land & Sea offered a torque-shift prop years ago, but that didn't go anywhere either. I was looking at the thing for our outboard powered boat at the time, but even with OB's it still looked like careful selection of a good quality high performance prop for your intended application was the best approach. Have not seen that approach really proved wrong yet.

The wetted surface of our boats is signficant and there is enough drag at speed that there's a point of diminishing returns with power or rpm's - not at all like a car that way (although if you watch top speed runs of Bugatti Veyron for example, the drag effects are pretty impressive when speeds are in 3 figures).