Offshoreonly.com - 540 heating up with stat installed

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- - 540 heating up with stat installed (https://www.offshoreonly.com/forums/general-q/210624-540-heating-up-stat-installed.html)

kreed

06-10-2009 08:39 PM

Quote:

Originally Posted by Boomer35 (Post 2885572)

why not just take the t-stats out? especially if its a carb motor... what temps does it run without them?

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.

Griff

06-10-2009 09:23 PM

Quote:

Originally Posted by PatriYacht (Post 2885016)

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

PatriYacht

06-11-2009 06:36 AM

Thanks for the info. It must be just the black motors that use the 160.

PatriYacht

06-11-2009 06:41 AM

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.

kreed

06-11-2009 07:29 AM

Quote:

Originally Posted by PatriYacht (Post 2885778)

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.

PatriYacht

06-11-2009 10:15 AM

Was the thermostat housing part of the kit?

kreed

06-11-2009 10:24 AM

Yes

stevesxm

06-11-2009 10:57 AM

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 ?

PatriYacht

06-11-2009 11:51 AM

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?

kreed

06-11-2009 12:47 PM

Quote:

Originally Posted by stevesxm (Post 2885967)

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.

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