Install drain plugs if don't have them.  I always drain water out of block no matter what.


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yep-

this one for flow (units):

http://www.usbr.gov/lc/region/g4000/hourly/DavisParkerSchedules.pdf


and this one for 'timing?'- look at Davis Dam Release cfs compared to Needles bridge cfs- (10am vs 10am, etc):

http://www.usbr.gov/lc/region/g4000/hourly/yester.html




Dan'l

I'm kind of a wiring nut though. Here's a dash I just did a last week for a customer.  Personal message me if I can help in any way.
Cheers!


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These are the water cooled flange high flow units with larger exhaust passages,  I believe 3 inch.   They flow much better than the restrictive smaller set...

Pressure is result of resistance to flow.  In order for flow to occur, there must be a pressure differential and a flow path.  There is no way that just the pump being submerged could cause any flow to occur.

On your boat (sitting level), the water pump mount on your block is about 10" above the cooling line fitting in the jet pump and the thermostat housing flange on the intake manifold is about 17" above the cooling line fitting.  Because the weight is aft, the stern will sit lower in the water than the bow, increasing these numbers.  The block won't even fill with water until you start the engine.

If you are observing flow through the engine while under way, that has to be produced by the jet pump.  I just can't see that the jet pump isn't producing enough flow to cool the engine yet produce enough flow to generate bowl pressure, and thrust,  with the water exiting a 3.125" nozzle opening.

Barring the possibility of a ski rope or something getting sucked up, winding around the back side of the impeller, and creating a seal between the back side of the impeller and the suction housing; the the restriction has to be between the jet pump cooling line fitting and where the water returns to the lake.  I believe you wrote that you tested flow in both directions.

I would lose the pressure relief valve.  I would verify that your gate valve is opening/closing all the way as it should be. Start with it all the way open and adjust down from there.

I also think Dan'l is spot on with what he just said.  I would add, make sure that the sending unit is getting a good ground.

Lastly, I would check your tune.  Tuning on the trailer is much different than with the engine under full-load.  You might be leaning out.  I will share this little tidbit; my engine leaned out, while cruising, as a result of a hose failure on the main fuel line between my fuel pump and barrel valve.  The engine got so hot that I could feel the heat radiating on my back at about 50 MPH.  It felt like the back of my neck was getting sunburned, but the sun was in front of me.  I run full pump pressure through my engine, which renders my water temperature gauge useless, because it never registers any temp unless I am idling for long periods of time.  The surface of the heads got hot enough to blister my finger when my dumb @$$ touched it.

Risers plugged with shit.

Pull the exhaust hoses and check for chunks.
Pull the 90 into the riser and check for chunks.

Check each log individually.

Does one side get hotter than the other?