Removal of thermostats

[steplift20]

My engine is a 150 Mercury outboard has two thermostats the call for 143 degrees. , what would happen if I removed them? The reason is because my engine over heated and I want to see if it is because of the thermostats or water impeller , the mechanic up here said that will be fine to take them out. Because I'm a cheap bastard I bought after market thermostats to save $15.00 learned my lesson. By OEM

[spareparts]

you need thermostats, or at least a restrictor in it place. You will not fill the block all the way and you'll have hot spots. If your Merc overheated, odds are its the water pump impeller. They have a poor deign water pump, I recommend a new one every year, if you haven't replaced the upper housing, replace that while you're at it. Check the lower housing, if teh seals look bad or it appears to have gotten hot, replace that as well. At the very least, check teh gasket under the lower housing. On the high performance stuff, we would remove the thermostats and run restrictors, usually a quarter with a hole drilled in it. It takes a while to figure out exactly what size hole to drill, lots of trial and error. Basic merc cooling system, water pump feeds water to the powerhead, once you get above 2000 rpm or so, you build too much pressure and the poppet valve drops off water pressure before it gets to the block, the thermostats open once you get the block up to tempo, btw, those mercs don't pee till the thermostat opens.

[steplift20]

What happened spare, last week I was out and thankfully close the the marina my over heat alarm went off so I hot her back and the mechanic at Barnes brothers here in nj told me it's ok to run it with no thermostats but I question that. I do have the old ones OEM to install and they look in very good condition. The after market one I put in to save money looked differant and cheap and ever since I installed them my engine would run hot, the pee hole has a strong stream so I figured that the impeller would be good till next year I figured if it still runs hot without the thermostats then it must be the impeller, and why don't they make a gasket for the thermostat housing, they should cause if I don't use gasket maker they leak ,I would rather use a gasket.

[spareparts]

the rubber grommets around the thermostats should seal them. I its peeing, teh thermostats are opening. Check each head to make sure they are both opening. A heat gun from harbor freight is cheaper than new thermostats from mercury. Temp stick markers are pretty useful as well. You can test your thermostats in a pot on the stove, open them up just enough to stick some string in them. Put a thermometer in the pot full of water. Hang the thermostats in the pot by the string. Heat the water, watch the thermometer and when the thermostats fall off the string, you know the operating temp. Or you could try a couple quarters, drill a 3/8 hole in them to start with.

[phatdaddy]

Does it run hot on the hose?

[steplift20]

Yes and it's hot also with no thermostats too but hotter with thermostats.