XR lower compared to Imco lower

Pure Energy · 03-04-2006, 08:52 PM

My mechanic has my drive to repair upper gears. He stated that the lower is usually the weak link in the XR. My uppers were probably damaged by abuse from previous owner.

I have installed a Whipple on top of a 600hp JC Performance motor and am looking to "bullet proof" my drive, if possible. Boat is a Superboat 30 Y2K, approx 5400 lbs wet.

Would an Imco lower be a better alternative??

Or a totally diff drive such as the B-Max

Or with careful driving and proper maintenance will the XR hold up?

Thanks

zt260 · 03-05-2006, 10:33 AM

What HP are you at now? That will decide your fate.

Vinny P · 03-05-2006, 10:58 AM

Besides the bullet, the Imco lower is about the same as an XR. The shafts are different but I am not sure they are any stronger. I am proof of that. They both use the same gears from Merc, so no difference there. I like the fact that the drive gear in an Imco lower is fastened to the vertical shaft with a huge nut, unlike the small bolt on the XR. Not sure how much of a difference that makes, but I just like it better. The Imco lower bearing carrier is billet, that would be better than Mercs. Imco claims their bearings are better, dont know how true that is. Most rebuilders end up using Timken bearings anyway. Wouldnt be surprised if Imco bearings are Timkens to begin with. They just charge you triple for them.

Pure Energy · 03-05-2006, 03:08 PM

600 hp + Whipple 2.3 liter

I am spinnig the drive left if that makes a difference.

BBB725 · 03-05-2006, 03:37 PM

I ran Merc XZ uppers with IMCO lowers for three years without any problems. Triple N/A 598ci 725hp motors

zt260 · 03-06-2006, 10:04 AM

Quote:

Originally Posted by Pure Energy

600 hp + Whipple 2.3 liter

I am spinnig the drive left if that makes a difference.

So what are we talking here? 800+HP?

Assuming that, you will be breaking a lot of drives. The BMAX will handle the most power out of the box. But the lower will still be the weakest link. I’ve blowen a few lowers, but never the upper. That’s with significantly more HP. Presently BMAX is switching out my lower gears to new coated gears. If it makes a season I’ll be happy.

Spinning left will make the drive more prone to failure. The top cap takes most of the stress. I would switch to right, especially if you use an XR upper. The top cap is pretty weak.

Pure Energy · 03-06-2006, 10:36 AM

zt260, thanks for the info. My motor is a 540 and I think it will be closer to 725.

zt260 · 03-06-2006, 10:54 AM

At 725Hp you have options.

The BMAX will last very well at 725, it will be basically bulletproof.

The XR can handle the power if it's setup perfectly and maintained. If you beat on it, it will break. I would upgrade some parts and go to right hand rotation.

You might want to consider another drive and having a spare. That's what I was doing a couple years ago. I'm selling my XR Sportmaster spare. It's in the swap section.

Panther · 03-06-2006, 11:57 AM

I have some IMCO Extreme's for sale in the classifieds and also and Extreme Upper.

How big is the boat and what is the weight?

ratman · 03-06-2006, 05:51 PM

cant advise you on the drives but i would check out the konrad unit. BTW

Quote:

I have installed a Whipple on top of a 600hp JC Performance motor

you might want to put a few extra layers of duct tape on the oil pan to catch parts that come thru the oil pan