Anyone put on on of these drives having problems with low water pressure? As part of my Whipple project I changed drives from a B1 with low pickups to an XR with the mid pickups (both strut and torpedo pickups). Now my pressure never gets above 10 - 12 psi. I had around 30 psi with the LWP. Dustin says I should have 20+ psi. Apparently there's a Merc. bulletin regarding this. Anyone ever modified theirs ?

Thanks,

Mark

So, your new XR drive has both the mid pick-ups and the low pick-ups??

And the swap resulted in less pressure than a B1 with only the low-pickups???

Sounds like water is escaping out the side inlets(outlets)...Do you have a high x-dim?

Wonder if you could block the side pick-ups...

I ckecked for bulletins and there's nothing...the only mention of water pick-ups is one that cautions you against shallow water... Gee, thanks Merc...

Nick,

Yes, the XR has both, but the low pickups are not as large or low as the old LWP's . Dustin Whipple has forwarded the Merc bulletins relative to this issue. Merc recommends plugging the top 4 holes of the upper pickups on both sides of the strut (they're sucking air with the stepped hull). They need to be tapped with a 1/16-27 NPT tap just deep enough so the plugs are flush with the surface. Dustin also suggests filing the lower pickups to enlarge them.

Mark

I have drive with both inlets for last 3 years. I do not know what my water pressure is, never worried about since motor does not ever run close to warm. Only time it gets past 100 is after motor has been shut down before starting back up again. Water comes out the exhaust & the intercooler outlet at speed so I must at least have enought pressure for that. I am going to say no matter how many holes you plug, unless you do all of them, that once the pressure gets too great it will releave excess pressure out the sides.

Beside your low pressure, any signs of motor not getting enought water? Running warm?

Turbo,

Thanks for the input. I've only had the boat out one time so far ($hitty weather) but the temps look fine - 100 -110 degrees on the gauge. Dustin said the concern with pressure is due to steam pockets, especially towards the rear cylinders. This can cause detonation. The high block pressure helps to prevent this potential problem. What are the detail of your setup?

Mark

Don't they only use 10-15lbs radiator caps on cars? I somewhat agree on possible steam pocket problems but have not run into any of those problems.

My concern would be when I pluged the holes am I disturbing the water flow around the drive. Could cause other problems in trying to fix one. I think if you increased the size a little on bottom that it would cause more water/pressure get to the pump. How old is your pump? Is your implellor going south?

My motor is 540, m4 procharger, dual carbs, 10lbs boost. & cmi's.