Themostat/crossover questions
 

OK, I have read the many numerous threads on here regarding thermostats and crossovers and the drilling of holes in the thermostats, etc.....but I am still a little confused.

Last year I removed my intakes to paint them, and at the same time I replaced my t-stats with new 140* Merc t-stats. The ones that were in there worked fine, so I'm not sure what I was thinking by replacing them.........too late now.

So with the new ones the temp fluctuates, it will climb up to 175* or so, then fall back to 140*. The old ones that were in there sat right on 140* all day long. I spoke to the guy I bought the boat from and he did confirm that he had to experiment with drilling hols in the t-stats to get them to work properly, but he didn't recall exactly what the final solution was. I have seen the pics on here of t-stats with holes drilled in the flange, however the t-stats I have don't have a flange wide enough to drill 1/8" holes.....then some say to drill holes in the body........???

I want to get this dialed in and resolved before I spalsh the boat this season. Please, someone help get me headed in the right direction. Thanks!

I drilled mine right in the side (body). I drilled three 1/8" holes, but I think next time I'll only do two.

175 doesn't seem all that hot to me. I like to try to keep mine at 160. My motor seems to run better at 160 than it does at 140.

Sometimes lower thermostats can cause more problems than they're worth IMO. What seems to happen is that the motor is generally over 140, so its always open, always cycling in new fresh water, and thus really not working (it's more or less the same as running no thermostat, but with a restriction in the line).

175* isn't all that hot, correct, but Merc built the carb 454 Mags with 140* t-stat for a reason. I would preffer to keep it consistant rather that have the temp cycle back and forth between 140 and 180.


jackhammer, I will try your suggestion, thanks.

I wouldn't want mine bouncing all around either, which is one of the reasons I use a 160. I understand that the motors came out of the factory one way, but so did that thermostat that you're planning on drilling holes in... I'm just sayin'...


I know guys that are fussy about keeping their boat cold, and they run without a thermostat. Their boats stay at around 120 or less all of the time, but they seem to always have issues with fouling plugs and other BS that I don't have to deal with. Their argument is that they would rather replace a bunch of plugs than a motor bearing... My argument is that they're wasting their time changing all that other stuff because 160 isn't hot enough to hurt anything anyhow, and I find that my boat runs better at 160.

To each his own...

I was told, many years ago, that the 140 was used because the salt crystalizes at the higher temps. I guess that would make it a non-issue for you lake guys. :)

Use the Hardin Marine style. My engine builder used these because they will not fluctuat from the crossover bypass dumping cold water on top. My original I put in fluctauted bad.
I too am having an engine temp issue but not from thermostat.