Merc XR2 Cooling System


I just installed my water pressure gauge in the dash and hooked it up to my engine (1987 Merc Blackmax XR2 150). I installed a new water pump. It is pumping out of the back of the engine, the 5/8th hose that goes out of the back of the cowling, and the piss tube is free of debris and is pissing very well. Did I take the water pressure from the wrong place on the engine? I took it from the top, but it is not registering on idle or high rpms, and nothing is coming out of the water pressure hose at the gauge. What's up? There are no kinks in the 1/4" water line. Why do I have no pressure? 

Okay, Here is the deal! 

There is no poppet valve, and no thermostats in the engine at all. ??????? Why would it be this way? I was told that it is an old racing engine. It has 149 psi on all cylinders. (I checked it 3 times, with different gauges, just to be sure). At the bottom of the engine on the right side, there is a 5/8" elbow with a 5/8" black hose. Water is dumping out of this hose pretty heavy, as well as the piss tube (tell / tale), after I rev it up to around 2000 rpms. 

How can I get water pressure to my gauge? Where else can I take water pressure from in order for my gauge to show pressure? It seems very strong and sounds great, but the mods that have been done to it are nowhere to be found on the internet, so far! 

If you know anyone who can help me figure out this thing, please forward this to them! 

Mike Lynch


I would get a service manual for that model and a parts book. Then put it back to stock. The way it is now is doing you no good. Run a XR2 like they designed it and your reliability will be much better.




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Mark C.


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