Help El Pescador 57 GSi Overheating

"Background- 2000 5.7 GSi 1.95

"Background- 2000 5.7 GSi 1.95 DPS running F5 props, 856 hours. Boat in LI Sound, WT has been between 72 & 76. Replaced manifolds, risers, engine water pump, sea water pump, thermostat housing and temperature gauge sender in 2007 at 639 hours as preventive maintenance when replaced both heads. Replaced outdrive intake hose (#3852352) and nipple last season. New impeller and thermostat this season at 807 hours. Beginning of June engine wasn't building temp above 120-125 degrees so replaced thermostat with new 160 degree, everything was normal (150-155) until middle of July when alarm went off after running at 3500 for about 15 minutes. WT never exceeded 160 on the gauge. Backed off and let cool but alarm has been coming on since, always around 160 on the gauge. I know it is WT related as the risers are equally very hot to touch, not warm like they normally ran. Checked everything obvious; impeller is like new, engine water pump is like new including the impeller, all hoses are clear, cleaned minimal growth from intake grills and back flushed through sea water intake hose. Removed thermostat housing, no blockage, checked thermostat and it opens at 150. I have performed the SELOC raw water flow test before I pulled the boat and it checked out okay. I pulled the drive today and the intake hose and sealing o-ring between the drive and shield are okay. I am stumped and before I remove the risers I would like your opinion on the possibility of PS oil cooler blockage. Is this common? With the ear muffs on, minimal water pressure running at 800 and the raw water intake disconnected at the thermostat housing, the outlet flow is more of a surge then a steady flow. Not sure if that is normal. The gauge is all over the place. It will rise to 200 then drop off to 140-150 and then bounce to 175 and drop off. It doesn't matter what rpm range. At a steady 1000 it will run for about 10 minutes at 175 and then climb. It wasn't doing this in the water. El do you have any ideas? Thanks, Ray"

"Ray,

First of all, I am n

"Ray,

First of all, I am not familiar with your particular engine model, and other members may have better ideas. However, since you asked, here are a few things you can try.

Since you suspect the p/s oil cooler, which is installed prior to the raw water pump, you may want to either back-flush it or rod it to prove it clear.

http://www.volvopentastore.com/Power_Steering_Pump_Gl_Gs/dm/cart_id.210667574--s ession_id.916608055--store_id.366--view_id.312797


One thing you have to keep in mind is that the raw water pump delivers a volume of water which is theoretically proportional to the engine RPM: that is, the higher the RPM, the higher the volume. From that volume of water, only one portion is circulated through the engine block and heads, and the rest is bypassed towards the exhaust manifolds without going through the block. If the pump is of the correct capacity (and I believe yours is), there should be sufficient water flow to cool the engine block and the manifolds/risers at any time. However, if the water flow is limited because of a worn pump impeller, or a restriction/air ingress on the pump suction side, or an obstruction on the discharge side (manifolds, risers, hoses), you may have a situation where there is enough water flow to cool the block (that's why the temperature does not go over 160ºF) but not the manifolds/risers. In that case, you have to check both the suction and the discharge sides of the cooling system.

Also, you cannot test the system with the ears on and minimal water flow, because the thermostat will be opening and closing continuously and will not be able to control the temperature (this is why the temperature fluctuates so much). You may want to try a large pail under the outdrive (large enough to cover until the cavitation plate level) and keep filling it with water from a garden hose while you run the engine."

"El,

As always you come up

"El,

As always you come up with great insight and I feel pretty silly around the cold water intake and the now obvious effect on the temperature control. So my best guess is a restriction on the exhaust side or air ingress on the intake side. The WT behavior is bizarre as it would always read within 125-140 when running with the ear muffs. I think my next move is to replace the intake hose with a clear hose and check for air ingress and go back to my former days of using the container under the OD instead of the ear muffs. I remain open to any suggestions from the board and will keep all posted with my progress.

Thanks, Ray"