Why dont boats have transmissions like cars?

Question

I know they have forward and reverse but wouldnt a gear shift be more fuel efficient?

Answer 1

Car wheels are (reasonably) attached to the ground. So most of the time there isn't any wheel spin. It the wheels are going slowly, the engine must be going slowly. Its a rigid system.

Boats on the other hand can throw water backwards at a huge rate when the boat is, initially, still only moving forwards very slowly. It is not a rigid system.

Therefore, a boat transmission can be set up with one gear, it will not need to change down to get going.

Answer 2

They don't need them; not the kind your thinking of. If the prop turns over a certain speed they get less efficient and fuel is wasted. All that is needed is a prop that is large enough to use all the torque driving it at the top rated power of the engine without excessive rpm. A big prop turning slowly at low power is still efficient. Very large ships do use transmissions to reduce the speed to the drive shafts since they have VERY large props.

Answer 3

i like cliffs answer but do have a few corrections to make: 1 he is right about the engine not being compatible for a marine environment. marine engines are built with all forged internals and stainless steel components to stand up to long duration of high rpms and corrosion from the raw water (the antifreeze in cars protects them from that kind of corrosion. boat engines also come equipped with a high performance cam as well as USCG approved carburetors, water circulating pumps, etc. the 2nd being that 351w were actually very common boat engines. though mercruiser never used them due to an agreement they have with GM. if your talking about a sterndrive boat, the most common applications for Ford engines were Volvo 270, 280, and 290 series drives as well as Omc Stringer and later on, Cobra drives. the best drive for the app. however is a Volvo Penta SX Cobra that volvo designed in collaboration with OMC before OMC went bankrupt and sold out to BRP. Ford engines were also very popular in competition ski boats in which there were in a direct drive setup. they were usually mated with a BorgWarner VelvetDrive marine transmission. and were a force to be reckoned with in the competition ski world If you want to use your engine, pull off the tranny. you cant use it in an 18ft boat and it would be useless in a larger boat even if it could fit. your gonna have to rebuild your engine with a forged crankshaft, connecting rods, pistons, and a new high performance cam designed for power in the mid-high rpm range. dont forget the USCG approved carburetor, waterpump, fuel pump, starter, alternator, distributor, and coil. if you try and stick an automotive engine in your boat, the engine will blow before it hits 40 hrs in the boat sorry to burst your bubble, but this will save you a lot of heartache in the near future

Answer 4

Most important is a flat torque curve, to give a smooth and linear throttle response, and as soon as boats get moving really fast, you get such nasty slam-pressure beating on the front of the hull - ever seen an up-ended speed-boat that was doing 50mph get smashed to pieces? I think the watercraft industry knows what it is doing.

Answer 5

Dont know the answer to that but with a face like that on your avatar I would seriously think about giving up the drink

Answer 6

its not required as the prop in water acts like a slipping clutch...

Answer 7

yes they do have transmissions

Answer 8

its the way of life

Answer 9

i have wondered that my self

Answer 10

My god is that you LOL