Tried back flushing and it won't clear. Can get through the oil cooler with flush but no further. From the diagram it looks like the only thing left is a fuel cooler and it looks like it's under the engine. The boat is a 353 formula. Any idea if the fuel cooler is accessible or if it's toward the front of the engine? I even tried back flushing with a pressure washer and the hose literally started to balloon so I backed off. Any other ideas? Hoping not to have to have the engine pulled.

I'm working through an overheating issue on a similar engine now, a 502 mag. What's your water pressure?

Can you better describe the conditions under which it overheats?

Since I can't backflush at all, I'm not cooling so it overheats pretty quick

Start taking off every water hose one at a time and back flushing each section indepently.

Thanks and that's what I did and I can flush all the way through the oil cooler but when I try to flush the hose coming up to the oil cooler, it's jammed. From the diagram, it looks like it runs under the engine to a fuel cooler and just trying to determine how to get to that so I can disconnet and see what's in there

Now I am really stumped. I can get water to flush from the fuel cooler up to the oil cooler (the way water normally flows) but when I try to flush the other way it wont go at all. My other engine flushes all the way through so I started wondering if this engine had a power steering cooler if there was some kind of a one way valve on it. Does anyone have any ideas?

You need to just start taking it apart piece by piece, and visually inspecting the coolers and hoses internals.

Agreed, I'm just at a point where I can't go any further w/o taking the engine out. It's odd water will flow one way and not the other. I can get a wire through the fuel cooler so I'm guessing it's soething in the power steering cooler which I cant get to. Any harm with gently running a thin plumbing router through the hose and/or up through the fuel cooler?

The hose that comes off the sea pump makes a 90 right after the pump and goes to the fuel cooler at the front of the motor behind the crank pulley. Mine plugged right at that 90 degree turn.

I found where the water won't flow. It's a blue and yellow cylinder with a petcock on it and its located between the oil cooler and the fuel cooler. I'll post a picture if needed but I have it out and I can blow air one way (the way water flows, but not the reverse direction. It almost seems like it's set up to do that (not allow water to flow in reverse). The weird thing is both engines have this and I cab backflush my other one. Let me know if a picture would help