Reply With QuoteDepends on the drive setup in the boat. Some of them like a vdrive have the same auto your car might have.
What is a boat transmission for and what does it do. I obviously understand how it works in a car, I just can't see how it works in the boat?
Depends on the drive setup in the boat. Some of them like a vdrive have the same auto your car might have.
I have a th400 in my 21' v-drive and it is good for coming out of the hole in second gear with tall gears and shifting to third and running it out. And you can shift to neutral with out disingaging and reingaging the v drive which usually has to be done with the motor off, and tall gears in a v-drive will idle faster than the 5mph zone will allow and also reverse for most but i have a whirlawy incase my shit blows up i dont go flying through the dash or flip the boat.
3 gears? I thought they blocked out thrid? I didn't see the sence in blocking it out. The direct drive versions are nice in the fact that you can pick the ratio that that will fit the boat the best and work with smaller props, cuz big props are hard to find, 30" pluss anyway.
3 gears? I thought they blocked out thrid? I didn't see the sence in blocking it out. The direct drive versions are nice in the fact that you can pick the ratio that that will fit the boat the best and work with smaller props, cuz big props are hard to find, 30" pluss anyway.
Usually 1st gear is left out because it is too low. 3rd is 1:1, and as mentioned, 2nd helps a high geared, heavy boat get going. Since a common V drive doesn't have reverse alot of boaters add the tranny for just that reason to make tight parking/docking eaiser. It should be noted that a trans doesn't remove the necessity of a whirlaway for any v driven boat that runs faster than about 60-70 MPH ..............MP
I was more curious about in more of the offshore setup's like in the #6 drives and what not. In a boat can you really shift to bring the rpm's down and maintain the speed?
I was more curious about in more of the offshore setup's like in the #6 drives and what not. In a boat can you really shift to bring the rpm's down and maintain the speed?
What you are looking for is an overdrive. I haven't heard of any 700 R4s in a boat. The standard Powerglide, and/or Turbo 350/400 units are not overdriven and the high gear result would still be 1:1.......So, you would have to gear it to run in a lower gear, (2nd) under normal operation, and just use the 1:1 for high speed operation only..........MP
I was more curious about in more of the offshore setup's like in the #6 drives and what not. In a boat can you really shift to bring the rpm's down and maintain the speed?
Yeah the transmissions that they use with the #6s are just F, N, & R because the #6s don't have an internal gearbox like a Bravo. Most don't have separate speeds. Some do and I think they all should have multi-speed trans', it would cut down on wear and tear on the motors. Weisman used them in the old Ettore offshore boat and a couple other offshore boats but they were all banned by APBA. I guess they have never really caught on. I've never heard of any problems with reliability with the Weismans but I don't know.
-Tom
I think the trannies are the weak link now between high hp motors and #6 drives. At this point I don't think they can make a reliable trans that can actually shift gears while under a load of a 1500 hp motor. I'm not talking about a 1/4 mile car either, I'm talking about a boat used for recreation all day up and down the lake. I don't see any advantages with top speed boats set up for kilo runs wouldn't benefit from shifting gears on the top end, although the hole shot and midrange could be better. Most guys with big hp don't care about the hole shot anyways, it does damage and adds stress to all the drive train components to drive that way. Hole shot speed is good for 1/4 mile jet and v-drive boats, not for 150 mph off shore style boats. As far as midrange goes, if you own a boat that does 150 at 6k and runs 100 at 3500 rpm, how much more midrange do you need?
I may be out of line posting this since I don't run 1500 HP or 150+ MPH but I have a 21' Schiada River Cruiser with a twin turbo BBC backed by a TH-400 trans with all it's gears. Of course, it's been modified to our application but I enjoy not having to lug the engine at low speeds by using the lower gears and it affords us the option of running taller V-Drive gears. We run 40% gears in the case so starting off in lower gears makes the transition from stopped-to-speed smooth as silk. If you pull skiers it's even more helpful (especially when the guys average 250 lbs. 6' 4" the lower gears are appreciated by the skiers.)
I"m confident there are cons such as weight but in our cruiser application it's "Just what The Doctor" ordered. We'd never run one in any of our flat bottoms however.
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