Another water pressure problem
 

I have a single step 35' Fountain with carbed 454's with gill exhaust. The engines are stock. I am currently pegging my 35lbs pressure gauges at WOT. I just installed drives with dual water pickups. The problem I had before with the side pickups was at WOT I was getting the pickups out of the water and having the pressure drop to 8-10 lbs. Besides putting in water dumps could the holes in the gill exhaust risers be enlarged to reduce pressure and improve flow? How large would you make these holes or is this a bad idea? Are there any sites that show the different dump systems? Any comments would be appreciated.
Dan

Good question Candyman. I have low water pick up bravos and stainless manifolds and risers and I peg the water pressure gage at 60 MPH. The boat did this with the stock merc exhaust as well. I figure it's just a matter of time and I'll blow the head gaskets. One would think that Fountain and Merc would have this crap figured out by now.

SeaDated,
All the ventilated Fountains seem to have a high water pressure problem. I gave a call to Marty Bosinger at Fountain and am waiting for a return call. There seems to be no firm consensus on how to BEST correct this problem. INTHERED had a picture in the Fountain section that showed his pressure gauges pegged also.

I use to max at 35lbs and start to drop as the pickups came out of the water. Now they’re pegged. I wouldn't mind if it were the Speedo that was pegged. :D

Dan

I hear you. A pegged speedo is definitly not something to complain about. Keeps me up to date on info from the factory. Thanks

Fountain is aware of high pressure in the 502's. They have talked to Mercury about the issue. Mercury's response is not to worry about it. Fountain says that 35lbs is not out of line on the 502's. Optimal would be 18-25lbs.

I called up Teague and they asked Norm what to do. He says there has to be a problem elsewhere and that should be found before adding a pressure relive valve. It seems if there was less restriction in the exhaust tailpipes the pressure would be less. I'll let you know if I figure out something.

Dan

Candyman I run Lightining headers on my Fountain that dump most of the water overboard and not through the exaust. There are only 4 holes maybe 3/16" that allow water into the exaust stream. The rest gets dumped out of a 1" pipe thread dump the actual hole is a little less than 3/4". I also run crossovers instead of recirculating pumps. I never see pressures over 20#. Cruising around 57 I read about 16#. Very little water comes out of tips and it is quite loud.

B.R.S.,
Thanks for the info. I think the exhaust would be limiting factor as to how much water can flow out of the tubes. If there weren’t enough capacity the pressure would build in the system.
I am thinking about putting a water dump out the transom. The pressure gauge that WETTE VETTE has looks good. Instead of running a tee after the coolers I was thinking of tapping off the center of the thermostat housing. Does anyone have any thoughts on this?

How did your bolster mounts work out?

Dan

Candyman I haven't got around to it yet but I think I'm going to use the the screw in T-nuts from rockler. Thet seem to be pretty slick. I'm not worried about corrosion with them because the fresh water up here is pretty easy on stuff.