V-DRIVE MAX RPM

[Pharmertim]

I am thinking about replacing my 2300 v drive mercruiser with a forged rod 400 sbc ?! Any ideas on the max rpm that the v-drive can handle or max output that the stock shaft can handle. I would like a little more but dont want to over do it and have to replace more than I could bargain for.

[dogbert]

I don't think you're going to have any issues if you can get to all fit together. They offered a 400+HP engine for a while.

[Pharmertim]

Im sure with gear on gear they can hold alot of power, but not alot of heat ?

I did notice on the dash there is a little light for v-drive temperature. . . so there has to be a maxium recommened rpm for these things somewhere. !? Maybe.

[chpthril]

Just curious, why? Whats your goal?

[R&T Babich]

...I did notice on the dash there is a little light for v-drive temperature...

I think the little red light on the dash (which is mislabeled "TRANS" on our boat) is the one that goes out at around 1000 rpm and indicates the internal pump pressure has reached above 2 psi so the gears will get lubricated properly.
There is another port on the V-drive housing where you could add a temp sensor that could trigger an alarm for excess temps.
There is a trans temp alarm sensor (190 deg - Alto Products Corp. ALT99329) for the Velvet drive that could be used on the V-drive.

[Pharmertim]

Just curious, why? Whats your goal?

Well, there are no 1st gear, 2nd gear, or 3rd gear etc in boats. . . . so lets say you have a 500 hp motor in a boat compared to a 350 hp motor with the same pitch prop. The 500 hp boat will obviously come up to speed quicker. . .but both boats will run about the same top speed if they both have the same rpm redline (say if the vdrive can only handle 5000 rpm from the motor ).

So to make use of the power of the 500 hp motor, you will have to get a prop with more pitch. Idling around picking up a skier or wakeboarder in the river, I dont really want it to idle the prop any faster than whats already there plus there will be more strain on the shaft itself trying to spin the prop with a larger pitch prop than compared to just building a motor that can handle 7000 rpms with long rods and short stroke and keeping almost the same pitch prop. So basically it will be like adding an overdrive to the transmission. Still having low and adding more high end.

My overall goal is to run 60 - 65 mph and still have power to pull a wakeboarder at 22-25 mph with a fatsac.

[dogbert]

Well, there are no 1st gear, 2nd gear, or 3rd gear etc in boats. . . . so lets say you have a 500 hp motor in a boat compared to a 350 hp motor with the same pitch prop. The 500 hp boat will obviously come up to speed quicker. . .but both boats will run about the same top speed if they both have the same rpm redline (say if the vdrive can only handle 5000 rpm from the motor ).

So to make use of the power of the 500 hp motor, you will have to get a prop with more pitch. Idling around picking up a skier or wakeboarder in the river, I dont really want it to idle the prop any faster than whats already there plus there will be more strain on the shaft itself trying to spin the prop with a larger pitch prop than compared to just building a motor that can handle 7000 rpms with long rods and short stroke and keeping almost the same pitch prop. So basically it will be like adding an overdrive to the transmission. Still having low and adding more high end.

My overall goal is to run 60 - 65 mph and still have power to pull a wakeboarder at 22-25 mph with a fatsac.

Ok, a couple of comments. It's not the V-Drive that's the limiting factor. As for HP, you need torque, not HP, because that ultimately is what drives your ability to push the boat.k

Finally, every boat has a maximum hull speed. I don't care how much power you throw at the problem, you're not going any faster.

As for your desire to make your boat go 60+, maybe you should consider a different boat. These boats are designed to throw a wakeboard wake with a lot of weight in the boat. They are not go fast boats.

[samw]

It just seems like a lot of work with little to no gain. Like Dog stated these are wakeboard boats made to do a specific task, being able to haul large amounts of weight and throw a large wake. That is why straight from factory your top speed is 40-45 max no matter what manufacture it is. You will not get the speed your looking for I could be wrong but I don't see it. But good luck in you endeavor. Let us know if you get this done.

[Pharmertim]

NOT to sound unappreciative of your comment, but I believe you are mistaken about horsepower vs torque. I have enough torque to currently pull 3 skiers with whats in the boat, but top speed will be based on the enigines ability to move the boat with force and speed = horsepower ! I am running a 13X13 prop and the boat has enough "torque" to plain out pulling whatever I can fit behind it. Changing the prop pitch would HURT my torque which is precisley why I dont intend to adjust my torque curve, just increse my propeller speed (speed = horsepower).

I was not under the impression that 65 mph would be too fast for a tige boat top speed !?! But Im glad that you responded to my post because that gives me alot more insight on what is possible with and impossible with this kind of boat. ! Realistically, what would be the top speed of this hull in your opinion ?

[Pharmertim]

It just seems like a lot of work with little to no gain. Like Dog stated these are wakeboard boats made to do a specific task, being able to haul large amounts of weight and throw a large wake. That is why straight from factory your top speed is 40-45 max no matter what manufacture it is. You will not get the speed your looking for I could be wrong but I don't see it. But good luck in you endeavor. Let us know if you get this done.

Well, I am going to have to pull the motor in replace it anyway, so I just figured on adding a little extra something while it is out. Its not alot of extra work to add forged rods and pistons since it has to be replaced anyway, maybe a little extra dollars. !

Some guy was telling me he had the 454 option in his ski nautique and it ran in the 50's stock from the factory. Im not planning on racing the boat or anything and I truely enjoy its purpose of wakeboarding. Just seeing whats feasable since I am going through the process anyway.

[dogbert]

I was not under the impression that 65 mph would be too fast for a tige boat top speed !?! But Im glad that you responded to my post because that gives me alot more insight on what is possible with and impossible with this kind of boat. ! Realistically, what would be the top speed of this hull in your opinion ?

I'd contact someone at Tige, they could probably tell you. Also, there's normally a max HP rating for most boats. I'd want to find that out also. Some of the newer boats had the PCM 6.0 engine which had 400 HP.

I don't care about top end. As long as I can go 34 Mph, I'm happy. That way I can ski. In fact, I've often thought about switching to a Diesel because they are more efficient and have more torque, which is what I'd need when we're surfing or wakeboarding.

To each his own. I will tell you that on your boat, the biggest engine they offered in those year models was a Mercruiser Scorpion, which had like 330 HP. I couldn't see paying the extra $8K for that amount of HP.

But, to answer your original question. Your V-Drive is a really simple mechanism. It comes in two gear ratios, 1-1 and 1-1.5. You may be able to contact Walter to see if they offer different set-ups. It's my understanding that these are pretty robust pieces of equipment that can handle a lot of torque. If you upped the gear ratio and boosted your power, you may be able to go with a higher pitch prop...to a point. At some point, the weight will overcome the prop and then you get cavitation (prop slippage). That's where hull speed makes a difference. These hulls are designed to throw a wake, not minimize resistance at higher speeds.

I'd guess that max speed on my hull is right around 50. I think I've had it up around that with my original prop. I can get it up to about 42 now. But, I can maintain speed more consistently which is very important for all the watersports we do. When I'm cruising around, I like to go about 25 so I can relax.

[Pharmertim]

Everything you have said is why I want to keep the pitch of the prop the same, maybe increase the diameter a little and just have it where the engine could turn higher numbers if I wanted to top it out a little more and not hurt the drive in the process.

If I just wanted more speed and less pull, I would buy a more agressive pitch. But I like to wakeboard and I dont want to go faster at the expense of less pulling power.

[dogbert]

You might try one of those new CNC machined ACME props. Check my thread on my 525 prop. I've got pictures of it compared to my 4-blade OJ. Didn't really rob me of too much top-end either.

[venetrex]

More power

The amount of power required to give the boat more top end needs to be like 2X. I repowered a 17ft i/o sunbird bowrider. It originally had a 2.3l ford with 110hp.. Was a dog out of the hole, like a really bad dog,. However it would do 42mph. When I put in a 351w ford with 290hp, realize this is almost 3x what I had and probably 4x the torque. I could race my buddies ski centurion direct drive skiboat. Out of the hole it was dead even until my boat planed, then I would basically run away. It was cool, and would do an honest 65mph. BUT it made NO wake and only held 6 people. When I needed a wake for airchairing I changed to my tige. The main difference is though that an i/o will plane out, and our inboards will not skim the water the same way. I think 50mph or 55 is the most you will ever get. Our boats are designed for out of the hole power. My 2 cents of the day