OMC 5.7 Cobra Running Hot, Low water flow

[metwrench]

I have a 1988 Nordic Crestline Rampage 21' with an OMC 5.7 Ltr Cobra. I have replaced Engine Thermostat, Raw water/Outdrive Water pump housing and Impeller with cage. Problem is at IDLE with ear muffs on water flow is 0 output at the Engine thermostat incoming hose. Becuase of this, The engine Heats up at IDLE only. When you rev the motor up, Water starts to pump. I have resealed and reseated the Raw water/outdrive pump twice plus checked for Clogs from lower screens to pump, and then from pump to Engine thermostat housing. Im wondering has anyone seen the Pipes that run inside the outdrive rot out ? or get pourus ? Has anyone run into this problem themselves ? Again, at High speed she spits water fine, Just at idle is the problem. For now I am using the boat, when its in the Ocean and above and idle it runs ever so slightly on the hot side ( bout 175 , Normally ran 160 ) Any help or advice appreciated.

 

[a.d.mobile]

Re: OMC 5.7 Cobra Running Hot, Low water flow

have you checked the ps cooler? pull hose on the intake side and stick finger in check for debris. next install a pice of clear hose between the t-stat housing check flow in lake/ocean should be solid with tiny air bubbles lots of bubbles means you are sucking air somewhere.

 

[Mikedg]

Re: OMC 5.7 Cobra Running Hot, Low water flow

Have you check the exhaust manifolds and risers? In salt water they are only good for a maximum of 5 years and may be clogged with rust.

 

[metwrench]

Re: OMC 5.7 Cobra Running Hot, Low water flow

Yes, I did check flow through the P/S Heater, There is No Restriction there. And I would think is the risers were plugged or Restricted that i would have water flow to the T-stat anyway ? There is NO to LOW flow at the hose that feeds the Engine h20 Pump. Again Yesterday I took the raw/Outdrive Pump apart and Look ( 3rd Time ) I also ran some Meriodic Acid through the water pump ports and down into the Outdrive Pick ups, I flushed, and ran engine with NO Change noted. I am now planning on Pulling the Lower end apart to get at the screen. Have anyone done this before ? Change the Intake Screen in the lower end ? I hope I find some kind of restriction when I start pulling it down. Thanks for the replies Guys I appreciate the Brain Storming<br /><br />John

 

[a.d.mobile]

Re: OMC 5.7 Cobra Running Hot, Low water flow

with the pump removed put flush muffs on and turn on water, is water coming up to the upper drive where pump is? it should just flow out about the same as hose pressure. how about a back flush with pump off pull hose from t-stat and put garden hose in and put pressure backwards to the drive?