I have a friend that is pulling his hair out trying to fix one of his motors in his Formula. The engine sea pump pressure is half of what the other motor is and goes into guardian mode. Just replaced all the manifolds, sensors, sea pump, risers, bellows, and t-stat. Removed and flushed the coolers. Upgraded the water inlet in the gimbal. I believe there has to be some water restriction for this to happen. I know nothing about the water drain system for winterizing the system and if that is even connected to the sea water side of the motor. What are we missing????

Does it have a fresh water flush system where you can hook up a hose and flush the sea water side out?

Baja and Formula and others tend to install a Tee fitting that has a spring loaded ball stopper in that Tee fitting. And that can get gummed up with seaweed and debris. I have seen this exact same scenario play out on a number of factory fresh water flush systems because of this.

Also, is he getting any water in the bilge when running? If this is the case, one of the air drain actuators is going bad, and allowing sea water to spill out of the system into the bilge.

Being a 2012 its probably an EC, happen to have a serial number?

possible poppet valve issue

Sensor ground and or harness issue ???

does the psi reading ever change --- Also What is water pressure psi with just key on engine not running ( KOEO ) and at idle and so on for rpms ? if the engine goes into guardian mode what fault codes pull up ? What is water pressure psi readings when it goes into guardian mode ?

These are a CAT engine and the cooling set up and exhaust is not that same standard set up.

ENGINE SERIAL NUMBER -- you can text it to me. Also there is possible PCM updates most likely for this engine if it has not gone back to a Merc dealer. There is many very long Service bulletins for the earlier 8.2 CAT engines. heck one is 30 pages long.

With that said engine serial number is a must and this will determine water flow / parts diagrams

2 of the best tests you can do is clear water hose testing in sections of the cooling system especially from inner transom and forward from there. Also water output tests after the sea pump outlet. Do not run long because of the cats in the exhaust. 15 seconds MAX to compare water flow output one engine vs the other.

Sea pump GEN VII internally scared not pulling enough water -- I WOULD DOUBLE CHECK THAT first and foremost and water output testing can help determine that as well

There is no flush kit and no obvious water in bulge or visible leaks. Is it possible the air actuators could be leaking air back in the system ?

Key on engines off 0 PSI. yes the pressures do change when engines are running and rise with RPM. one engine seems to be almost 1/2 PSI as other even at different RPM's. Trying to get serial number now.

I pulled the hoses on both of the engines at the power steering coolers where the psi senders are located with water still going through the coolers and dumping right at the cooler. I got 0.0 psi running on the bad engine and 0.6 psi on the good engine. So that leaves me to believe the issue is between the outdrive and power steering cooler? I also took it a step further and check it after the oil cooler, allowing it to free flow out of the oil cooler and got 2-3psi on the bad engine and 5-6psi on the good one. Please note the engine has a brand new OEM seawater housing and pump as well as a new water pickup hose in the gimbal. I am now questioning the fitting on the starboard exhaust manifold that plumbs to the sea water pump hose.

After looking at the plumbing diagram I never payed any attention to the popoff valve. If that was stuck open could that cause the problem? It looks like its just part of a recirculation loop? What's its purpose?

serial number will help per the set up. I will see when you get it. . Thanks

s/n 2a042709

Randy did u check the fitting thats in the gimbel that the hoses hook to... Bravo fever ??? that closes up over time and restricts flow