Im about to install three 555 ci. engines in a 42 cig, the engines r producing around 640 hp and 665 torque. it is a 1990 with wut i believe are original drives. What is the minimum drive i could run wiht this boat. Also what would be required in switching to some used #3 speedmasters(costs, speed loss). I am very easy on the drives, but i dont want to be breaking drives every weeked waiting to be able to use my boat.

what are your original drives? bravo or trs? # 3s will be tough to get parts for and you'll have to move the motors forward for trannies.

i dont think you need to go to #3s. why not go with custom built XRs or Konrads?
you could probably get away with stock XRs, but you'll need to be easy on them.

20, 000 for drives,+ 6,000 for transom assemblies

bravo shop, max machine worx, teague, billet can all beef up xrs for your needs

There is a new Xr coming out for the new 600 called the xxr. may be just what you need.

xxr? sounds like what we ALL need!!!

they are bravos, so is the only tihng i need to replace the drive itself?

you may want to consider HP gimbles as well. While the motors are out. Do it right the first time.

If you are easy and smart you will be fine with your bravos, asumming no air time. I ran 950hp with bravos on a 42 fountain with very minimal problems.One gear set and a couple of shaft, Replaced with imco parts when broken and no future breakage. I did ease onto plane and drove reasonable, I did race just about every weekend though, 110 mph. Just my experience.

Well, you could take the chance, but examin your gimbles closely for any sign of stress or cracking, replace your gimble bearings. And I would have the drives torn down and rebuilt, just to be sure. all it takes is one bad bearing to take out the entire drive. bearings are cheap for piece of mind.

good luck

Stinger,
There are several options open to you. If MTI says he could make a set of regular Bravos live with that power in front of a standard Bravo on that big of a boat, I believe him, but also commend him!! 42' of boat is quite a load and I have seen people break drives in all kinds of combinations and if they are not careful they can break every weekend. Knowing what will break a drive helps.

You can upgrade your drives to XZ or XR gears and upgrade the lowers to XR large shafts, or a mix of after market shafts that will improve their chance of survival. Proper set up and assembly is another important factor.
I, from experience, would recommend upgrading to the HP gimble. That is an important link to the back of the boat and when it fails it can be violent.
You can also buy new XR drives and the install kits for them that go into the transom assy. You can also look at the Bmax, Konrad, Arneson, etc.
Depending on the condition of what you have, you can go several routes. Upgrades, new, etc. No one wants to toss money away, but done right the first time and care when driving and you can save money in the long run. IF someone has had good luck with this combination, as MTI says, you can have the same luck.

I would suggest tearing down the drives to see what you have, then go from there. If you have some one local do it, find someone that actually works on High Performance drives and measures the case and sets them up for proper lash of the upper gears. Most just assemble per the Merc manual and dont really do justice to the end product.

I hope this helps. If you have any more questions, fire away or feel free to email me.

Dick

how much labor is involved in tearing down a drive, also if i were to strengthen the drives which parts would you replace, or if i were going to rebuild the whole drive what places will rebuild the whole drive with xr parts?
thanks