Crossover vs stock circulating pump
 

I have a Mercury HP 500 carb engine, all new set up back to factory specs with the exception of a better spring set. I installed a new crossover and thermostat housing in place of my original Mercury circulating pump with a 160 degrees thermostat, I am noticing hotter temps ranging from 200 to 225 even at almost any speed and steamy exhaust. I live in Gulf Shores Alabama and our water temps haven't gotten really cold yet, should I re-install the circulating pump rather than use the crossover on this engine?
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Did you drill holes in the thermostat? I have been using one for several years and has worked well, I have also found that the high flow thermostats work a better.

Yes I drilling 4 small holes around the outer perimeter of the thermostat itself, then re-installed it. Engine heated up fairly quickly to 200 degrees again. Not much water flowing through exhaust tubes either. I had hoped this set up would work fine, I like it so much better than having to have that circulation pump installed, but at the same time want the engine to run cooler.
I am wondering if I should try it without any thermostat before taking everything back off?

Also, does anyone happen to know the exact timing setting on the Merc 500 carb engine? I have been told it was 8 degrees but want to be sure. Thanks to all whom respond.

dont run the thermostat!, i could be wrong but i have the crossover with hp500 carb. its gonna run really cool hell i live on the same water as you do and on a hot day my temp wont hardly get over 150deg! dont just take my word for it get on the do it your self page and make sure, ive had this set up for 3yrs and i dont run thermostats!

Thanks, I plan to keep the set up if I can, no reason for it not to work. I plan to check for some restrictions at the transom and check the impeller, which was good before. One way or the other, I am going to cover this issue! My wife used to have a 89 Cafe Racer! Nice boats.

You nead to make sure your oil Temp. Is getting up to 212 or you will have condensation in your oil. And your water psi stays under 20 psi.

Do you have a by-pass so exhaust gets water when the thermostat is closed? If you don't you can't use a stat. They also make restrictor plates that help slow down water flow and build a little heat. Also your oil doesn't have to get over 212 degrees. 190-200 is fine.

got a pic of your setup? I would consider going back to the circ pump though..... more consistant temps ...and water Pressure ....you really gain nothing ....m

I would check your water pressure. With a good high flow stat you shouldn't be that hot. If you don't have a bypass, get one. I run in colder water, but even with a 650hp 524, I barely hit 150 with a 160 thermostat. My biggest problem with my system is the right side runs 15 degrees cooler than the left.