View Full Version : 1993 PS 190 - Thermostat issue

05-21-2010, 01:09 PM
We have a 1993 PS 190 which has always run too warm - around 190-200 degrees. We've changed the thermostat (160 degree from Skidim) several times, changed the water pump this year (the large one mounted on the engine) because the bearings were starting to squeal, changed countless impellers, and back flushed the system. We even replaced the temperature sender unit last year. I also have a raw water strainer that is clean. After all this, the engine still wants to run about 190-200 degrees.

At this point, I removed the thermostat completely last weekend and the boat now runs about 125 degrees.

So I guess I have a couple of questions....

1) Is it bad to run the boat without a thermostat if the temps are going to run about 120-125 degrees?

2) Any suggestions as to why several different thermostats have allowed the boat to run hot?

3) Would you suggest buying another thermostat, but getting a 142 degree instead of a 160 degree?

I'm just at a loss why the boat has always run warm and at this point I'm pretty content just to run it without a thermostat unless that will cause permanent damage.


05-21-2010, 01:52 PM
Where are you getting those 160s?

Try the 142(3). Do not run at 125 degrees.

05-21-2010, 02:07 PM
Skidim (http://www.skidim.com/products.asp?dept=1091).

I see I mistyped my first post - I did mean the 143 degree thermostat when I originally wrote 142.


05-21-2010, 03:53 PM
For what it is worth..I run a 140 in my boat and it runs around 160 and mine is a 93 190

I did have a higher tstat in mine so that I could run a hot water shower and the water would not get hot but warm before I added the 160. Since then the shower has been removed and a lower temp tstat has been installed.

Just Askin

Have you removed all of the hoses and looked for blockage, including the tranny cooler screen?

I would remove the twist style drains on the block were you winterize and try to run compressed air or force water back up them. Take brass fittings and thread them into the block and make some kind of set up to hook up to a garden hose. Southern engineer a 3/4 fitting some how down to a 3/8 (I believe that fits into the block). I would run some pressure through the block backwards some how.

I am also curious to see if maybe the guage is bad. The temp sender is based off of resistance. Measure the ohms on the sender at the highest temp. Maybe one of us can take a multi-meter to the lake and measure what ohms are close to 180 or so. Those who have lower tstats can wait with the engine off and wait a few min and the temp will be higher at restart and you have to measure fast as the temp will drop fast.

I would dump in a 143 in and see what you have before doing the ohm test but if you need one of us to do it we could probably round up someone to give you a reading.

05-21-2010, 06:34 PM
I would check timing also. And I would not spend another dime until gauge is verified as ok.

05-24-2010, 02:55 PM
When I was a kid I had a 1967 Firebird that was constantly overheating. After trying many things (thermostats, cooling fans, radiator etc.) i found that a previous owner/mechanic had installed the water pump without the baffle plate. I don't recall if there is supposed to be one on the 351W or not. Just a thought.

Worthing skier
05-24-2010, 06:03 PM
Hi there

I went throught the same drama , i have a 1993 prostar 190 with the 285 inmar , did a couple of impelers , t/stat , sender unit , made no difference , then checked the actual temp of the coolant with a thermoeter only fine that it was running at the correct temp as per the t/stat 140.
So checed the gauge only to find a bum earth , cleaned it up , now runs 140 all day .
Back of the gauge you should a 3 wires 12v feed , earth and supply from sender .

Good luck