Merc 4.5L 250HP

[8gv]

I think the car/boat comparison gets off track due to the use of multi speed transmissions in cars.

Yes today's cars get great performance with less displacement. Much of that comes from improved valve train and injection technology. The delivery of that performance requires gearing. Does anyone recall cars with a two or three speed automatic? Now it's 6, 7, 8 or a CVT.

I'd like to see some torque curves on the engines in question.

[Biggd]

How long before we see electric boats? Tesla is developing some of the fastest cars on the road. Will we see some of these engines in boats soon or will electrics not mix well with water?

[Dave R]

Originally Posted by Biggd

How long before we see electric boats? Tesla is developing some of the fastest cars on the road. Will we see some of these engines in boats soon or will electrics not mix well with water?

They already exist, but are extremely limited in range due to the huge difference in power density between petroleum and batteries. I think the best batteries have something like 5% of the power density of petroleum. Some day, that will probably change dramatically. I think graphene will make batteries, motors, solar cells, and conductors in general, vastly more efficient and compact in the next few years.

[ITD]

Originally Posted by Dave R

They already exist, but are extremely limited in range due to the huge difference in power density between petroleum and batteries. I think the best batteries have something like 5% of the power density of petroleum. Some day, that will probably change dramatically. I think graphene will make batteries, motors, solar cells, and conductors in general, vastly more efficient and compact in the next few years.

I don't even think it's that good, 5%. Once it gets better, I would say even to 30%, the IC engine for road travel will disappear quickly.

[Dave R]

Originally Posted by ITD

I don't even think it's that good, 5%. Once it gets better, I would say even to 30%, the IC engine for road travel will disappear quickly.

Considering how small the fuel tank is on a modern car, having batteries take up 3 times the space to give the same range would be fine, IMO. In lab testing, graphene-based batteries, have proven to be rechargeable pretty much as quickly as you can feed them electrons, so recharging could take mere seconds with them, especially if you used graphene-based conductors in the charge cord.

[robmac]

I just got off the phone with Merc and the engineer I spoke with stated" We are going back to forging and casting our own engines for several reasons which at this time can't speak about at this time" so there you have it

[ITD]

Originally Posted by 8gv

I think the car/boat comparison gets off track due to the use of multi speed transmissions in cars.

Yes today's cars get great performance with less displacement. Much of that comes from improved valve train and injection technology. The delivery of that performance requires gearing. Does anyone recall cars with a two or three speed automatic? Now it's 6, 7, 8 or a CVT.

I'd like to see some torque curves on the engines in question.

The transmissions allow the engines to remain in their optimum power band, maximizing efficiency increasing gas mileage. In the case of the Chrysler ZF transmission, it actually shifts so fast that in the Hellcat Challenger that the 0 -60 and 1/4 mile times are fast for the auto than the manual. These auto transmissions are huge technological breakthroughs and they keep squeezing more and more ratios into those transmissions. I think one company is up to 10 or 11 for an automobile.

Transmissions do not increase engine horsepower, they actually decrease it due to mechanical and system losses.

[8gv]

I concur.

My Subaru with its CVT is no race car but it does ok when called on to do so. A rolling start helps get the CVT to perform without wasting high revs.

[Dave R]

Originally Posted by 8gv

I think the car/boat comparison gets off track due to the use of multi speed transmissions in cars.

Yes today's cars get great performance with less displacement. Much of that comes from improved valve train and injection technology. The delivery of that performance requires gearing. Does anyone recall cars with a two or three speed automatic? Now it's 6, 7, 8 or a CVT.

I'd like to see some torque curves on the engines in question.

A muti-speed transmission would be a waste in boat, 2 speeds would be more than adequate (well obviously, since single speed transmissions have worked great for decades...). One thing to note, adding gears will not make the boat faster or appreciably more fuel efficient, it will only improve acceleration.

There have been a few attempts at two speed transmissions in boats. I think the luxury brand Riva still offers one. Mercruiser used the planetary gear section of a GM 2 speed powerglide transmission to make a marine 2 speed that fit behind their I/O engines about 20 years ago. If memory serves, they dropped it from their line quickly since it did not sell well.

An ideal solution would be a planetary gear set that takes the place of (and fits in the space of) the coupler on an I/O and uses an external brake to stop the ring gear (and shift into low). The shift to high would be accomplished by simply releasing the brake which would let the ring gear spin freely. With the brake released, the entire gear set would spin at engine rpm with no gear reduction and little load on the oil in the gearset. Planetary gears can handle huge amounts of torque for their size and may work great with today's smaller engines that make losts of HP but not so much torque.