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Cooling issue/ low pressure w/ 150 Mariner Mag III

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BIGFLAT

Contributing Member
Changed the water pump (kit) in March. No change in water pressure. ( old impeller looked real good) Pulled and cleaned the poppit. No change. Ran it with out thermostats, ran it w/o poppit, no change in water pressure. 8# at 4000. Tattle tale stream looks real good. My record book shows when I changed the water pump in '08, I had 14# at 4000 rpm's. Now I have only 8#. Last trip out, without the poppit in it, I did not have any temp spikes. Coming in the temp only got to a lil less than half of the gauge.(water 80*) I let it idle when I went to get my truck to load up. About 3 minutes passed, and steam was coming from the tattle tale. My thoughts are that I have a plug somewhere. Any suggestions as where to start? Thanks...BF
 
Took the fitting out of the top of the block where the fitting swages down to go to the poppit, thinking at that reduction from 1/2 to a 1/4 there might be a restriction....Clean as a whistle. Looked down that opening with a flash light, can't see any thing obvious...Now thinking the gauge or the tubing to the gauge might be the problem. Anyone ever had the line to the gauge cause low readings? Gauge is out (hello wasp nest) to get checked out for accuracy. Any idea where one can get that small plastic tubing? Thanks for the help...BF
 
Chris, I don't know about a pressure sensor. I have 1/8" rigid plastic tubing from the engine to the dash. I'm trying to locate a new piece to change it out and eliminate all possibilities. I tried running a piece if saltwater leader thru it and can't get it to go all the way thru. Won't get the results of the accuracy of the pressure gauge til maybe Tuesday. Thanks for your input...BF
 
BIGFLAT said:
Chris, I don't know about a pressure sensor. I have 1/8" rigid plastic tubing from the engine to the dash. I'm trying to locate a new piece to change it out and eliminate all possibilities. I tried running a piece if saltwater leader thru it and can't get it to go all the way thru. Won't get the results of the accuracy of the pressure gauge til maybe Tuesday. Thanks for your input...BF
Click to expand...

Disconnect the tube from the engine and screw in a mechanical gauge.
 
Well..... The gauge checks out fine..Dead on at 15#... So what do I do now. My thinking is I didn't do something correct in installing the kit on the water pump. Any suggestions??? One thing that concerns me is the way the vanes are supposed to be on the impeller. Is this important?? Someone suggested to me about the tightness of the screws that hold the cover plate...I ready to pull the lower unit (Whoopee!!) Thanks for you help on this...BF
 
I suspect you're loosing water going to the power head. The tube must not be sealing tightly at the LU or at the top where it attaches to the power head adapter.

Jeff
 
How does one check that the tube is not sealing at the top??? Can I take some thing soft like wood or plastic and tap the tube to be sure its in all the way??? I put a piece of electrical tape on the tube that goes into the pump housing to assure a tight fit, but not on the end that goes into the tube that goes into the block. Seems reasonable that maybe the tube , after 17 years, might slip out of the block. Thanks again to all for sharing your thoughts on this problem...BF
 
It hasn't slipped all the way out, but the seal up there could be burnt up/ cracked etc. The power head has to come off to do it right. Sorry.

Jeff
 
I don't ever remember that it got that hot, hot enough to get burnt up. Never that I can remember it ever got hot. Never,ever seen my temp gauge get to 3/4 of the gauge. Hope you're wrong. But thanks for responding. I'm gonna pull the L/U off when I have time and have someone who can come help me get it back on ...BF
 
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