540 heating up with stat installed
06-10-2009, 08:39 PM
#31
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I have had the stat out.(single engine). But am getting alittle condensation in the breathers. Thought giving some water temp might help. Plus, everyone telling me not to run engine cold. Water temp doesnt move with no stat. Oil temp goes up to 140-160 when I beat it up. But then goes back down to 120. Just thought it would be better for engine running it with alittle heat in it.
06-10-2009, 09:23 PM
#32
Charter Member # 55
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The EFI motors are supposed to have 160 deg. thermostats. The computer will think the motor is still cold with anything less and tend to run rich. A cross over with a bypass is meant to run with a thermostat Mine runs rock solid at 120 degrees with a 120 degree therm. and 2 1/8 holes drilled in it. My bypass uses a 3/4' hose, how large is yours? Oil temp lower than water temp doesn't make a lot of sense. I would double check the gauge. If it checks, then the problem is likely related to water flow. Check all of the usual things, impellor, hoses, make sure nothing is plugged etc.
Actually the 500EFI's use a 140* Tstat. I thought they used a 160 too until somebody said differently and I double checked on www.mercruiserparts.com
06-11-2009, 06:41 AM
#34
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I would like to see a picture of the plumbing also. Some thermostat housings are not designed to be used with a crossover. Water from the by pass interferes with the temp sensing part of the thermostat preventing it from opening. A picture could give us a clue.
06-11-2009, 07:29 AM
#35
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When I ordered the crossover, It actually came with a braided bypass line and a 140 stat with a 1/8 hole drilled in the outer flat of the stat .Thats how it came in the crossover kit.
06-11-2009, 10:24 AM
#37
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Yes
06-11-2009, 10:57 AM
#38
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i may have missed this in the beginning but let me ask this... has the motor EVER maintained the correct STABLE temperature with the crossover kit as installed from new ? in short... has it EVER worked and is this something new or has it NEVER worked as delivered ?
06-11-2009, 11:51 AM
#39
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My motors are proof that crossovers and thermostats work. I also know of many others with similar systems. The problem must be elsewhere. You said water pressure is too high. I'm assuming that's with the thermostat open because you say it's maxing the gauge at 3500 rpm. The gauge sender is at the intake manifold so the only restriction left after that are the exhaust manifolds. Have you checked the exhaust's for corrosion or other blockages? Did you ever get around to checking the gauge?
Last edited by PatriYacht; 06-11-2009 at 11:54 AM.
06-11-2009, 12:47 PM
#40
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Well, I had it on a different engine last year, but without a thermostat and no bypass hose. Now, with a bigger, and alot more expensive engine, Im trying to help it last and perform well as long as possible. So, I did use the crossover but without a stat. Put the stat in this year w/ a bypass line, the water pressure shoots up and the 140 stat goes to 180 to 200.
