Rebuilt Oberdorfer raw water pump and now engine temp rises with RPMs

[SeaFever]

Paul,

Somehow I feel that your problem may not lie in the raw water input section. You indicated that you are getting the water coming out of the exhaust and that it increases with rpm. That makes me feel you have a problem somewhere else. Interestingly you say that the problem was created after you rebuilt the pump and before rebuilding your pump the engine was working fine...

Perhaps you could try uninstalling and reinstalling the pump. You should also check what dgill has just suggested. I don't know about the long and short screws, and don't understand the reasoning for the same so cannot infer whether that could be an issue. Ron will be able to help with that.

I would just recheck everything that you touched while doing the rebuild of the pump. Sorry don't seem to be of much help to you...

[Ron Hill]

Paul : What D. Gill is saying is that the metallic coating on the engine compartment insulation might be "shorting out" the temp sender.  Here are two things to try :
1.  Run the engine with the insert over the engine removed  -  if the temp still shoots up then that's not the problem
2.  Run the engine and take a IR thermal gun and get the temp reading of the thermostate housing and the surrounding metal area - and see if the temp is really what the gage says.  The temp sender could have gone bad ?

A few more thoughts toward solving the problem

[SeaFever]

Paul,

I don't think this is related to your problem, but I came across something interesting in another forum.. The water pump in question was an Oberdorfer, however the engine was an A4.

The sailor found that the new impeller was slightly smaller in 'width/thickness' than the original one. See the attached photo.

I found it very interesting and thought I would share it with you and this forum. Such a thing could result in lower water flow. Again as I said, this may not be your issue, just related information. I also believe it is a different kind of Oberdorfer pump for the A4.

[pablosgirl]

All,

I went to replace the zinc anode in the heat exchanger this weekend as part of my regular maintenance routine and low and behold the old zinc was so encased in salt deposits that I could not possibly insert the new one.  So I pulled the HX from the boat and took it home to clean it out.  When I took the cover off the zinc anode end I could not see the face of the tube sheet through all the salt that had accumulated in that end of the HX.  So I took a screw driver and dug out the salt.  It was nearly 1.5 inches thick, till the inner edge of the cross support for the end cap bolt.  Once I had the salt out of the end and could see the tube sheet, I knew that this was the source of my rise in engine temp with RPMs.  About half of the tubes were either partially or completely obstructed with salt.  Taking the end cap off the other end where raw water lines enter and leave the HX, there was minimal signs of salt build up.  I had this end off looking for impeller bits after I rebuilt the raw water pump.  The only thing that I can think of was that the three weeks the boat sat idle while I was rebuilding the raw water pump was enough time for some of the tubes to completely close up.

I then took a wire coat hanger and cut the long straight part out and used it to rod out the tubes.  I ran the wire in and out of each tube while running the garden hose over the tube sheet face to flush the salt out of the tubes.  This did not take long, maybe 20 minuets.  I then installed the new zinc anode and the end caps with new rubber gaskets and o-rings. 

Once assembled I installed it back into the boat.  I took this opportunity to replace all the raw and fresh water hoses.  Since on disassemblely I discovered that the raw water hose from the HX to the anti-siphon loop right before the injection nipple into the exhaust riser was cracked right at the hose clamp on the HX.  It tore at this spot when I pulled it free from the HX.  After removing this hose I discovered another spot on the hose where the hose was worn through to the wire reinforcement where the hose was rubbing against the cutout in the bulkhead on its way to the anti-siphon loop.  Without regular inspection, who knows what mayhem lurks in the dark recesses of your engine compartment!!  After I installed the HX, I ran the engine at 2500 tied to the dock and the engine in forward for 20 minuets, water temp did not go over 165 deg!  Problem solved!

Paul Shields