View Full Version : engine temperature question

john jones
07-23-2011, 01:06 AM
I took my 89 tristar 351 to the river today. I had installed a new 160 thermostat because I found some impeller piece in my old one and thought it would be a good idea.

When I got it installed the boat was running around 170-175, so I re-installed my old one and it runs between 160-170. When I push the new thermostat open the spring feels heavier than the old one.(not sure if that is why the cooler temp)

Should I try to drill my new thermostat? If so how many hole and what size?

I have looked at the trans cooler, changed the impeller and looked inside all the hoses.

Is it possible that my waterpump is going bad? It isn't squeeling or leaking

thanks for the help

07-23-2011, 09:48 AM
this is interesting because i just installed new thermostats along with my new circ pump this past week and had the same thing...running 170-175...i got a new impeller coming.

07-23-2011, 09:55 AM
It just sounds like the new thermostat just has a little stiffer spring and wax pack. If you dont wanna run at 175 then run your old one as it sounds like it still works, but the new one will probable loosen up a bit after a while. All you need is one small hole at the top side of the thermostat, and thats for incase the thermostat ever fails in the closed position you don't stop all water flow.

07-23-2011, 10:05 AM
The STANDARD thermostat is a 142 that runs at 160. The 160 is usually for a HEATER that will run 170-180. The best advise is get a MARINE thermostat. Very important

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john jones
07-23-2011, 10:11 AM
Should I worry about 175 temp?

My old one runs around 16-170, should I try drilling a hole in the new one and see what happens? If so what size should I drill it.

I am new to this boat, maybe the temp is acceptable, I just figured I better check.

Later, I will post my timing question :)

07-23-2011, 10:27 AM
Personally I won't worry about 175, but like jim said make sure its a marine version as a marine thermostat are brass and won't corrode like auto zones best will when used in a marine environment, use a 1/16 " drill bit to make your hole

john jones
07-23-2011, 10:43 AM
that could clear it up, I have a heater in my boat, so the 160 would be correct. I guess the 170-175 isn't a problem.

Thanks for the help!

07-23-2011, 10:53 AM
I run a 142 thermostat and it holds a constant 160 temp. I found a 160 thermostat pushed the temp to 175 - 180 and caused more hot start issues and vapor lock. Don't know if it is true however I was told that running too high of a water temp on raw water cooled engines cause water sediments to become deposited on the engines water cooling passages.

john jones
07-23-2011, 11:02 AM
Nvrgvup, are you running a heater in yours? When you had a hot start issue would it crank but not start? Or not crank very hard?

07-24-2011, 02:57 PM
No heater in mine. It would crank fine just not start very good when hot. Thermostat helped. What cured the hot start issue was adding a ballist resistor jumper wire from the starter solenoid to the output side of the ballist resistor which leads to the + of the ignition coil. There is actually a post for this on the solenoid which is connected in parallel to the post for the starter wire. The bypass gives the coil more volts which means stronger spark only during starts to counteract the draw of the starter.

07-24-2011, 08:54 PM
Hmmmm. Mine is a 142 and my gauge sits dead on 140.

07-24-2011, 11:41 PM
Now that I think about it I can't confirm that it really is a 142. The shop put it in so maybe it is not, that is what they said was specified. With whatever stat is in there it runs at a constant 160. At least that's what the gage reads.

Does thermostat temp typically equal water temp?

07-25-2011, 08:44 AM
Hmmmm. Mine is a 142 and my gauge sits dead on 140.

agreed. My 142 will not hardly ever get me above 140. I cannot get my 91 to get over 150 unless I run WOT forever!

07-25-2011, 10:17 AM
agreed. My 142 will not hardly ever get me above 140. I cannot get my 91 to get over 150 unless I run WOT forever!

There are a few guys here with the Maristar 220VRS's and the factory stat is the 142. If we install a 160 stat some times the motor will not restart once it is shut off. Let the motor cool down for a few minutes and it fires right back up. I tried a 160 degree stat because my exhaust smells a little rich even after replacing the cap, wires, and plugs. Could just be my imagination (the smell) because my plugs all look normal.