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Merc 175XR2 Cooling Hose Configuration

J

JSWIFT

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I have a 2000 175XR2 powerhead attached to a merc jetdrive. The head temperature guage is indicating 155-165 degrees F which seems a bit warm. Currently, the cooling water hose comming off the heads vents to the pee hole fitting and the cooling water hose at the top of the block terminates to the exhaust on the adapter plate. Is there a plumbing configuration that would help me lower the head temperature. Would venting the head cooling hose to the exhaust and venting the block cooling hose to the pee hole fitting lower the head temperature?

JSWIFT
 
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Quiet forum! Suppose I re-plumbed each cylinder head cooling water hoses to terminate at a pee hole fitting. In other words, have two pee hole fittings instead of having one for both heads. Anyone see a problem with this configuration to lower the head temperatures?

JSWIFT
 
Why do you want to replumb the engine to solve the temperature issue? Why not fix it? Is the gauge /sender correct? The parts diagram calls for a 143 F. thermostat. Have you tried changing it?
 
Thanks for the reply GUYJG. New teleflex gauge and sender. No thermostats ( common on jet applications and hot weather operation) . Good pee stream. Flushed system. Temperature increases with power settings. Temperature slowly drops as power is decreased. Timing set conservatively (18 degrees@ full power). Makes me think cooling flow could be improved. I've seen a couple cylinder head cooling hose arrangements. This is a merc 2.5L powerhead ie same as that on an outboard. Going to verify temp with an IR temp gun. Any suggestions on getting it to run cooler?JSWIFT
 
Negative, recent rebuild and never been in saltwater. Just came off of break-in mix (25:1). Someone must know of a way to get this engine to run a bit cooler.

JSWIFT
 
Is this increased temperature issue from day one of the reman? Did you pull the thermostat and tested it? Increased power causing increased temperature sounds like a water flow issue.
 
Yep, higher temp issue from day one. No thermostats in housings. Garden hose stream from Pee hole fitting at full power. Took it out today and it ran about 155-160 degrees at full power( but the water temp was a bit cooler today than on previous days). I agree that it sounds like a flow issue, that is why I am considering two pee hole fittings, one for each head. Still need to check temp with an IR temp gun. Any other suggestions GUYJG?
 
Yep, higher temp issue from day one.
Click to expand...

If the impeller is new then one can assume that either not enough water is getting pulled into the waterpump or the hot water can't get out fast enough. Things to check:

Water tube may be partially blocked w/old impeller chunk
wrong impeller installed
impeller housing/gaskets defective or installed wrong--sucking air
partial blockage after water inlet before the pump--sand or packed mud
wrong or defective gasket somewhere in the cooling water path
 
Thanks GUYJG. You've given me some things to consider.
Same impeller in very good condition( no chunks missing). O-rings checked when I rechecked the water intake holes in the wear ring of the jet drive New hoses coming from heads. Going to back flush system again and verify temperature with an IR temp gun.

JSWIFT
 
Same impeller in very good condition( no chunks missing).
Click to expand...

If you remove it does it hold a set position or will the blades open up? Replace it if it holds set blade positions. Cheap insurance.
 
Remember, this is a jet drive on a 175XR2 powerhead. Your talking about a water pump impeller, and I'm talking about a jet drive impeller. Cooling water is forced into 4 holes inside the wear ring by the rotating jet drive impeller, up through the adapter plate and into the block. No water pump on this application. I've checked the 4 cooling water holes and they are clear. The garden hose stream( a good 3 foot stream) from the Pee hole at full power shows no indication of a blockage which has me scratching my head. Good rule of thumb on the rubber water pump impellers though.

JSWIFT
 
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