Show us your Water Pressure!
 

I'm curious if the step Hulls are running high numbers for Water Pressure. In the off season I fixed my sucking air into the system by installing dual water pickup Bravo X drives. My pressure doesn’t drop even in a hard corner. The problem is that I am pegging the water pressure gauge. I know this will create engine problems and I am franticly looking for a solution. My understanding is that the 502's were the worst offender of High water pressure. I'd like to see what kind of water pressures we are all running. I believe Inthered had a picture of his dash with the gauges pegged.

My current water pressure is 35lbs +
With the old drives and low water nose cones the top pressure was 35 port and 30 starboard which then dropped to 10 lbs. as the pickup came out of the water.

Thanks,
Dan

Dan,

At wide open throttle I have 25 lbs of water pressure and around 8 at idle

GATORONE,
They obviously have those 575's dialed in.
Dan

Candyman

I'm with you ...35+

Sea Dated,
Bruce suggested adding holes into the tailpipe section, which makes sense. I have one water hose going to each manifold.
Does your setup have one or two?
Dan

candyman

Only one hose to each manifold.

I just got a new 29 with a 500 EFI/XZ. The Merc book says water pressure should be 20-30 lbs @ wot. I only get 13-15 lbs which is what the Fountain report says that they got. Pressure at idle is just barely visible.

If that helps.

Thanks for the responses so far. As long as there is volume 10-15 lbs. is good. Marty, at Fountain, likes to set up the race boats with 18- 25 lbs.
I'd like to hear from some of the other 502 and 454 owners. The 500’s don’t seem to have this problem. The are only two causes I can see for high water pressure in a normally operating engine. Sea Dated and myself have the thermostat housing with only one hose going to each exhaust manifold and that might be the restriction or the exhaust manifold it’s self is the restriction.

I new I should have bought the HP500's.;)

Dan

Candyman

Me too. I went to get a 32 with 500's and then I found another one with better looking graphics, to me anyway. I wished I had the 500's now. Drats!

My 29 w/HP500 (carb) is about the same as envision's. Nothing to just a tick at idle, around 15 at WOT. Drive does not have the low water pickup arrangement.

Jana,
Thanks. It seems the 500's don't have the problem, which still makes me suspect the thermostat housing on the later 502's and 454's. My water pressure at idle is about 2-3 lbs.

Dan

2k 29' 500HP EFI 25#+ Wide open ... Low water pickup Bravo.

Sea Dated,
I spoke with Gary @ Grimes Auto Marine in GA who makes the water pressure relief system that MIKEHTMSR24 and RumRunner were speaking of. A very knowledgeable person with race boats. He was evolved with Don Johnson's race boat. That boat had a dump system because of high pressure.

He believes my restriction might be in my tail pipes, not the number of holes in them but the amount of room between the two-jacketed tubes. To confirm this he wants me to tee off the thermostat the hoses that run to the manifolds. I am supposed to put a gate valve in line and have the end of the hoses run over the side. He wants me to run the boat up to 3500 and check the water pressure. Then both valves are to be opened evenly till my pressure drops to 20 lbs. then I am supposed to take it to WOT and repeat to get the pressure to 20lbs. During this time I need to monitor the engine temperature to make sure there is no fluctuation.

The next step is to leave the valves open and bring the boat back to idle. I need to keep an eye on the engine temperature, pressure and riser temperature. If every thing stays the same I can run a dump system without a pressure valve otherwise I need some sort of valve to keep the system with some pressure. The numbers we want for optimal performance is 18- 24. Anything under 16 lbs. at WOT can cause hot spots in the heads. Anything over 24 can cause gasket failure.

I plan to try this set up next week and will make a decision on what to do. The other option would be new exhaust. :( My current exhaust is mercury/Gill manifolds with Rex Marine power flow tail pipes.

Dan

candyman, mine is also the Merc/Gil exhaust. The clearance between the two pipes is more than enough to flow whatever your pump can pump. There is around a 3/16" space all the way around between the 2 pipes. If the exhaust is the restriction, it has to be the 3 holes that are drilled in the end of the pipes. Possibly they are plugged up some?????? Don't you have 2 hoses going to each exhaust? 1 to bottom of manifold, 1 to the tee at the manifold/riser bypass hose. It would seem the easiest check would be to simply run one of the hoses at that tee overboard. If your pressure comes in check, that would mean your problem is in the riser itself, and not the stat housing or the ex. manifold. If the risers do prove to be the restriction, open the holes up some with a dremel.

US1 Fountain,
There is only one hose on the newer 454's and 502's. The hose goes to the exhaust manifold. The water flow then goes through a by-pass hose to the riser. I was thinking of going to the two hose system with the tee at the riser. But after speaking with Gill and Rex that shouldn't be the problem. The risers are not from Gill they are from Rex Marine.

I like the relief system you came up with for your motor with the crossover.

I can't wait to hear some more numbers from members with 454's and 502's in single, twin or triple’s.

Thanks for the responses,
Dan

Dan, your right. Whether there are 1 or 2 hoses really makes no difference. It all still has to flow thru the risers.

Hey, I got an idea. Run without the risers, That'll say if they are the culprit. :p :D

Good Luck
Jerry

US1 Fountain,

When I saw your name I thought you were going to post 0 lbs. :(
Hopefully it's something cheap and stupid. I have been paying 70.00 for the Seawater rebuild kits. I hate paying list prices.

Dan

i had the big 0 psi today. i forgot to swtich my valves and burned up my impeller. damn damn damn.

:D :D :D Good one!

Yeah, it was something stupid, but never cheap! Damn muffs!

where is the best place to get the sea water rebuild kits?

Dredgeking,
A local marina has been giving me 20% off list. I would think Dollar or Bam would also be doing at least 20% off. Mike from Dollar treated me great and had a great price on my drives. There was also a post in the for sale section from a marina in Canada that said he could save us some money because of the exchange rate. I never got around to calling him and can't remember his name.

Dan

i ordered from teague today. it was $68 for the kit. not too bad.

And I just bought a kit from a Searay dealership yesterday for a sweet tune of $95

Anyone with a 95-98 454 or 502? What kind of water pressure are you getting at WOT?
Thanks,
Dan

candyman35,

99 27' 502 MPI. 30-35 psi at wot just like the test sheet says.

Took apart my manifold/risers for the EGT probe mod for the Whipple install, lo and behold, rust spots in manifold. Cyls 3 and 5 the worst. Contemplating what to do next. I'm considering CMI's but the credit card's getting maxed!

Breathe Later,

I saw the pictures of your manifolds. When you winterize do you drain the block, leave water in it or use antifreeze? You wouldn't think they would rust through like that.

You are running some high water pressure numbers. Fountain claims that 35 lbs. should be ok. They did inform Mercury that they thought 35lbs was high and Mercs response was it within limits. :confused: If your Whipple has an intercooler with a dump it should reduce the pressure. Let us know how the project works out.

Thanks,
Dan

candyman,

Winterize has been with real antifreeze-the green stuff with corrosion inhibitors. The boat is stored inside on of our warehouses that is maintained at 60 degrees. The rust inside the manifolds was caused by a leaky manifold to riser gasket. A small leak weeps water inside the exhaust manifold where it has a straight shot to the two inner exhaust ports. Mine was fairly minor as I caught it early enough. Since we have all sorts of neat stuff at work like a bore scope, I was able to peer inside the cylinder through the spark plug hole. Not enough water leaked to get inside the cylinder.

Mark S.