57 Running hotneed help diagnosing

"Ok, need some help here from

"Ok, need some help here from you experts!

2006 5.7 EFI running hotter than normal at higher RPM. Bravo 3 drive. Always runs 170, lately at 2500rpm and up, running 200-210.

I just replaced the thermostat. Took boat out on run, same symptoms. Fine at lower RPM, heats up quickly at 2500 rpm on up.

I then changed the impeller. Ran boat, same symptoms again.

I then took off all the hoses (at different times), started engine and checked flow. I have more than adequate flow from every hose. Even flushed them with fresh water from garden hose and got adequate back flow outside the boat. No visible obstructions or clogs anywhere. Boat is in the water so makes it easy to perform these tests.

Now...... at higher RPMs, the starboard riser is hot, and I mean HOT!, the port riser is normal temperature, warm but not even close to the starboard temp, I can't even hold my hand on the starboard riser for more than 4 secs.

NOW WHAT?? Help!

What else should I be checking and/or replacing?

Thanks!!"

Was the impeller in one piece?

Was the impeller in one piece? No? Find the pieces by back flushing the hoses from the hot manifold and riser.

One piece impeller? Yes. You may have a bad exhaust shutter preventing exhaust and water to exit fast enough. Exhaust manifold and riser could be plugged w/debris. Gasket may be plugged. Remove the riser and check it. While you are there look at the shutter.

Guy - yes impeller was perfect

Guy - yes impeller was perfect.

Follow Guy's advice. You h

Follow Guy's advice. You have a blockage of water flow to the stbd riser for some reason. Start at the T'stat housing and go right thru the stbd side.
Rod

"The saga continues....

I t

"The saga continues....

I took off the starboard riser this afternoon, inspected it and it is clean as could be, not plugged up like suspected.

The marian mechanic stopped by and said that he just had a similar issue on an identical boat. He said the hose from the drive to the water pump used to be made of copper, now it is flexible and collapses at higher rpms, thus restricting flow. Could this be the case? He said they contacted Merc and the fix is to pull the entire engine to access the hose! I find this a bit overkill. True?

He also said on the other boat, they chose to repair it by installing a Y valve on the secock from the generator and greated a new intake area and totally bypassed the intake tube from the drive. Is this ok? He said that they can drill another intake and install a seacock thru hull and run a new line.

HELP!"

""used to be made of coppe

""used to be made of copper, now it is flexible and collapses at higher rpms, thus restricting flow"

I would tend to believe what Merc. is saying. It seems the marine mechanic has come up w/2 simpler solutions.

"the starboard riser is hot, and I mean HOT!"

For some reason the starboard riser is either getting all the hot engine water or little water at all. Interesting.

What do you other boys think of the solutions?"

"The mechanic said that the ST

"The mechanic said that the STBD riser is getting hotter becasue of the way the water flows through the ball diverter or somehting. Then he looked at it and said "Wait, you don't have that setup" then moved on to something else, not answering my question why STBD riser is way hot."

What does running lean mean? C

What does running lean mean? Could that be the cause of one riser to heat up substantially?

My srbd riser is also hotter.

My srbd riser is also hotter. Not as hot as sr75 but I think this is causing my anti knock to take over and reduce my power. Have you experianced that?

"Hot riser has to do with wate

"Hot riser has to do with water flow to it or through it. Find the blockage or diminished water flow.

"...riser this afternoon, inspected it and it is clean as could be, not plugged up like suspected..."

Can you see inside it? What about hidden obstructions of rust. Remove all fittings and dip it in (CAUTION--DANGEROUS CID!!!) muriatic acid for 90 min. and rinse well and clean the passages w/a stiff wire passage brush."

"Hey Guy. Took off riser again

"Hey Guy. Took off riser again, cleaned thoroughly, also water passing freely through manifold. Same thing happening, STBD riser ho, port cool, temp. guage rising at higher RPM. If the water feed line from the drive was kinked or twisted reducing flow, wouldn't BOTH the SBD and PORT riser be hot??"

"wouldn't BOTH the SBD

"wouldn't BOTH the SBD and PORT riser be hot??"
One would think that would be the case. What does the starboard exhaust manifold feel like? I suggest that you get a lazer temp. gun to get actual temps. to help diagnose the problem. What gasket are you using between the manifold and riser? Have we discussed the starboard exhaust shutter? Since it is downstream of the exhaust it could be part of the problem or there is a blockage between the shutter and the bottom of the "Y" pipe. Zebra mussels can make a blockage very easily.

"guy, I am using the 4 open po

"guy, I am using the 4 open port gasket, not the restricting one for the closed system. How easily could I check the exhaust shutter? Do I need to pull the riser off again, or is there a better way to check it? And... what am I looking for?

Thank you...."

"To check the shutter, remove

"To check the shutter, remove the rubber exhaust hose after the riser. The shutter should be at the top of the "Y" pipe. It is a folded metal device w/a rubber edge. Look into the "Y" pipe w/a mirror on an extension rod (like a collapsing antenna) and flash light to see if a mouse built a nest in it last winter. Use an extended set of mechanical fingers to probe the lower pipe for debris. Flush it w/a garden hose on jet setting and see if any debris comes out the lower end."

"Had almost the same problem w

"Had almost the same problem with my 454 magnum today when I took off the oil cooler which is located on the front of the engine just below the oil filter I found the debri that was blocking my water flow. Problem solved maybe this will help you. My sea pump connects straight to this cooler on the bottom and then another hose connects to the plate above the thermostat, the oil line connects from the filter to the top of the cooler and then from the bottom into the engine just from pulling off the hose on top you would never know it was blocked it looks like a strainer that only water could pass thru but the sea pump comes in at the bottom hose and when I removed it I found it was totally blocked from an old impeller and other trash."

could the oil cooler cause the

could the oil cooler cause the stbd riser to run hotter than the port riser?