Harper220

I need to install a pop-off valve on one of my 496 HO's. I'm doing it because the drain valve on the starboard side leaks when I go over 50-55 mph and then fills the bilge very fast. I can not reach it to replace it or diagnose it, but I know that's where the water is coming from. Where is the best place to install a pop-off valve like the one DANA Marine offers? I can not reach anything on starboard side of my motor, so it will have to go on the port side.


http://www.danamarineproducts.com/Pr...9&CFTOKEN=1800

hoozeyurdaddy

have you done something to increase your water pressure?
what psi are you running now? you can add the pop-off anywhere on the pressure side of the water sys. where there is a 1/2" plug, but it sounds like you need to fix the problem and not put a band-aid on it, pull the drive and lift the motor, it shouldn't take much disconnecting to raise it enough to get to the valve.

dana marine products

Be cautious in installing any provision that will possibly bleed off water from your cooling system. 496 engines are very sensative to any added heat.

You don't want to start another problem where your tripping heat sensors on the motor.

Harper220

I really don't know why the heck it's doing it. I added IMCO shorties a few years ago and the other engine was doing it, so I just recently replaced that drain valve and now the other one is doing it. I really don't think its putting a band aid on it. It's just allowing the water to drain out the pop-off valve rather than the drain valve into the bilge. The entire engine would have to come out to replace the drain valve and then I take my chances of the new one doing the same thing. If I had them pull the engine, I would just have them remove the drain valve and just re-plumb it. I think they're a joke and have had nothing but problems with them boating on the Missouri river.

Harper220

What do you suggest I do then? Isn't that what a pop-off valve is for? It's better that the water is dumping over board than in the bilge. I'm not pulling the entire motor to replace a $200 drain assembly that might possibly do the same thing.

So since you're with DANA, where would you suggest I install the pop-off valve? Many others have suggested that a pop-off valve is exactly what I need. I'm a bit confused now???

GO4BROKE

iTrader: (1)

I don't think those valves are meant to relieve excess pressure. As I understand it they are only for draining the blocks for winter storage. They certianly arent meant to fill your bilge. Although I'm sure all the hot water is cleaning it nicely! I think you need to check your pressure, and then figure out what you need. Probably a relief valve and fix the leaking drain is my $.02

dana marine products

To start, I've never experienced a stock Merc 496 fitting leaking externally.

I'm merely trying to offer a ittle advice on installing any provision that will will bleed off water on a 496 engine. Most engines don't have heat sensors that are capable of shutting the engine off. If we were discussing this situation on a 502, we wouldn't have to worry about incidently bleeding off too much water at specific times causing the exhaust to run 15 degrees hotter. Just be cautious in what you're attempting to do. The heat sensors in the exhaust are very sensative and if activated, they will put your engine into gaurdian and/or shut the engine off.

The brass pop-off valve we offer is mainly designed to sit in the pressure side of the plumbing system (after the pump). It will bleed off excessive water, mainly in water spiking situations. If the boat leaves the water, when it re-enters the water pressure will spike and potentially cause problems.

Every application is different, one boat that's running 65 mph isn't going to have a problem in this area. A boat that runs 120mph is going to pack alot more H2O into the system when it's running hard. That's why the pop-off valve exists, and that's why it's adjustable.

I'm not saying you couldn't make this work, I don't know if it will solve your problem, but you can probably install it in your system, get it adjusted properly so it won't trip the sensors. Just be aware that the sensors in the exhaust are sensative.

The stock fittings are half brass/half plastic, some early model units are all brass. The cup that houses the check ball is not the strongest design we've seen. Most likely a loose or cracked cup is causing your issue. Taking water away from the system is a band aid. The stock system does not require it. I understand your position of the work level to fix the problem.

As far as too much water PSI causing the problem, not likely. The inbound water feeds the heat exchanger. It's then sent to the exhaust from a pressure fed system. It's not a direct system. Example, if one exhaust manifold has an obstruction, water will simply exit out of the other side. The water volume the exhaust system can absorb is almost double what is traveling through the system. (1) 1 1/4" coming in and (2) 1" hoses leaving. If that scenario did occur, Mercury has fail safes installed on the engine, one being a high pressure switch which if activated will put into guardian mode. The second being the heat sensors in the exhaust. The obstructed manifold will overheat, trip the sensor and shut down the engine.

Your exhaust manifold is set up with (1) 1" hose entering and (2) 1" hoses exiting (riser hoses). The reason the system is set up that way is because of the factory drain back system. The stock Mercury lower manifold fitting has (2) barb fittings. One accepts the incoming 1" water hose which is above the check ball. The second fitting is a 3/4" barb which is below the check ball that accepts the drain back line. The drain back line is connected to the main 1 1/4" incoming water hose. The check valve above the 3/4" barb is simply a floating ball that is controlled by water pressure. There is no spring. As long a the water pressure in the incoming water line supercedes the water pressure in the exhaust manifold the floating check ball will be forced up closing off the drain back system. This insures that all exiting water travels through the exhaust manifold. If you have a scenario where the water pressure in the exhaust manifold supercedes the water pressure in the main water line, the floating ball valves will be forced open bleeding off up to 40 percent of the exhaust manifold cooling water. This will cause the exhaust sensors to trip and will naturally raise the water temperature of the engine. Up to 40 percent of the hot water that has already passed through the system will be sent through again.

The risers have (2) 1" hoses to make absolute sure the exhaust manifold pressure does not supercede the main 1 1/4" water line pressure. When someone wants to drain their water system, you connect the air pump, pump up the heat exchanger, and it holds the check balls open so the water can drain out through the main water line.

Sorry for the novel. I hope the above info helps clarify how the system works.

Harper220

Thanks DANA for your input. Raylar had posted in another thread that the 496 drain valves will open up at 45 psi. I bet he could shed some light on this issue. When the drain valve is leaking at higher speeds, I don't experience any spike in temp or any heat sensors going off.

bowtye8

I thought I just had somthing similiar. I popped some fitting on the stbd exhaust manifold. I had higher h20 pressure about 30-38. This is a piece that screws into the bottom of the manifold. has a tee with one hose coming off then goes lower to a plastic type fitting that has a nipple with a hose clamped on to it. That plastic fitting popped off. I'll have to snap a pic to describe it.

Does the sea pump go directly to the heat exchanger or to the pwr steering cooler the oil cooler then the heat exchanger????

Raylar

Two things in your post about the drain valves stand out. One you have changed the drives to IMCO shorties and you boat in the Missouri river. A drive change with their modified type pickups could raise your water pressure and boating in the water of the Missouri can add debris to your water system especially if you don't have sand and silt strainers on each engine. Before you start guessing whats wrong you should get a scan tool hooked up to your motors and go out and run the 55-60mph where you are having the trouble and read the actual system pressures in each engine. There have been drain vlaves of the 496's that have failed at 20psi pressure and even when 25-35 psi pressure is standard on a 496 at high rpms.
A pressure relief valve may solve the immediate problem of the drain valve pop off, but you may expierence total drain valve release later and still have to replace or bypass it.
Find out what pressure your systems are building and then go from there, don't guess and use the "Dart Board" approach.

Best Regards,
Ray @ Raylar