Water Pressure relief Valve
04-18-2002, 10:18 AM
#21
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Nevermind the picture, I just looked at a setup like yours in a hotboat magazine. The restriction is more than likely the plumbing that connects your manifolds and your tailpipe. The type of dump valve HTM Mike or that I am using should work just fine. Tee it in after your oil cooler in your main feed line.
04-18-2002, 05:37 PM
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WETTE VETTE,
Thanks for the help. I am going to run the boat with one of the thermostats pulled to see the pressure readings. My "Band-Aid" fix will be the McMaster-Carr valve. I was planning on tapping the thermostat housing and running a line to the transom. Do you see any problems with that? The water line on my boat comes right out of the cooler and makes a hard bend right into the T-housing. Thanks again for the help. This is driving me crazy!
Dan
Thanks for the help. I am going to run the boat with one of the thermostats pulled to see the pressure readings. My "Band-Aid" fix will be the McMaster-Carr valve. I was planning on tapping the thermostat housing and running a line to the transom. Do you see any problems with that? The water line on my boat comes right out of the cooler and makes a hard bend right into the T-housing. Thanks again for the help. This is driving me crazy!
Dan
04-18-2002, 10:00 PM
#23
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I don't see any problems with tapping the thermostat housing. Just tap it 3/8 or 1/2 NPT and if it doesn't work put a plug in the hole. I know it will work if you tee in right after your oil cooler, but it takes a custom made tee. I know the feeling of being frustrated, but it will be worth it when you get it straightened out.
Good luck.
Good luck.
04-19-2002, 11:32 AM
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I just got of the phone with Gary. What a great individual. His first guess is that my problem is in the tailpipes. He gave me some good ideas on how to diagnose the problem. He wasn't interested in selling me stuff. He just wanted to help. Thanks Gary and the guys that are so happy with his products.
Dan
Dan
04-19-2002, 11:50 PM
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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
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
gary grimes
04-20-2002, 08:16 PM
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are the pressure spikes caused by the pump losing head pressure as the boat is coming out of the water, then suddenly getting the pressure back and then water hammer effect as the pump gets more pressure as it fills the suction hose as it re-enters the water? if so, wouldn't it be easier to fix the suction side for the spikes?
here is what i was thinking, a small tank, filling from the top from your water pickup. the outlet, off the bottom of your new tank, going to the suction of your raw water pump. possibly, a small vent tube overboard off the top of the tank to vent air. as you have a couple spare gallons of water on the suction if you come out of the water, your raw water pump is still spinning, sucks the level down in the tank a little, and it makes some room for the surge of water that will take place as you re-enter the water and keeps a more constant head pressure on your pump reducing or eliminating the spikes in pressure.
you would need to calculate the gpm of water flow when airborne , the time your out of the water , and make the tank roughly twice the capacity of the that the pump will use when out of the water. i'm just thinking out loud. any thoughts on this idea? Fran
here is what i was thinking, a small tank, filling from the top from your water pickup. the outlet, off the bottom of your new tank, going to the suction of your raw water pump. possibly, a small vent tube overboard off the top of the tank to vent air. as you have a couple spare gallons of water on the suction if you come out of the water, your raw water pump is still spinning, sucks the level down in the tank a little, and it makes some room for the surge of water that will take place as you re-enter the water and keeps a more constant head pressure on your pump reducing or eliminating the spikes in pressure.
you would need to calculate the gpm of water flow when airborne , the time your out of the water , and make the tank roughly twice the capacity of the that the pump will use when out of the water. i'm just thinking out loud. any thoughts on this idea? Fran
04-20-2002, 08:25 PM
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i forgot to mention that the water pressure too high problem could be helped by reducing the head pressure to the pump by increasing the vent size off the top of the tank if necessary.
04-20-2002, 09:28 PM
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Excaleagle42,
I wish that were the problem. I know the race boats will use a large sea strainer to prevent running out of water. Now I have found they also have a pressure relief to handle the spikes. My pressure is constant on calm water. It is rpm oriented and not speed. Thanks for the input. I should have things worked out by next week.
Dan
I wish that were the problem. I know the race boats will use a large sea strainer to prevent running out of water. Now I have found they also have a pressure relief to handle the spikes. My pressure is constant on calm water. It is rpm oriented and not speed. Thanks for the input. I should have things worked out by next week.
Dan
05-05-2002, 08:53 PM
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Water pressure update! I put a tee off of my exhaust manifolds hooked to a gate valve. With this valve fully open I could only eliminate about 10 lbs. of pressure. Pressure dropped from 45lbs
to 35lbs. I went home and re-rigged the system with a tee just after the coolers before the bend into the thermostat housing. I ran a 1" line through a ball valve and then out of the boat. With the valve a little more than half open my pressure dropped to 20 lbs. 
I am going to order some pressure valves in the morning.
This is a Band-Aid fix. I believe the problem is the plumbing of the thermostat housing and not the exhaust. The motors are stock 97 Mercury 454 Mags with only one line running to each side of the exhaust. I plan to test this theory over the summer by installing an older style T-housing. I'll keep you posted on the progress.
Dan
to 35lbs. I went home and re-rigged the system with a tee just after the coolers before the bend into the thermostat housing. I ran a 1" line through a ball valve and then out of the boat. With the valve a little more than half open my pressure dropped to 20 lbs. I am going to order some pressure valves in the morning. This is a Band-Aid fix. I believe the problem is the plumbing of the thermostat housing and not the exhaust. The motors are stock 97 Mercury 454 Mags with only one line running to each side of the exhaust. I plan to test this theory over the summer by installing an older style T-housing. I'll keep you posted on the progress.
Dan
