Why not run a thermostat in jet motor?

[dm2bfree]

Kind of newbie questions I suppose.. I don't use a thermostat in my motor, I adjust through a gateway valve to keep my 460 motor temp around 160. I don't run it cause I was told that I shouldn't, but I'm not sure I understand why it's bad. It would keep the motor at the right temp the whole time right?

[MADDOG355]

There is a special setup for running a thermostat, But the short answer is It will build too much water pressure. Try the forums at performanceboats.com or riverdavesplace.com Both are more into the Jet/V-drive style boats than this sight is now.

[jetboatperformance]

The only way to effectively run a T stat is with a 4 port bypass system , not nessesary IMO ,but definatley available ,You cant simply install a T stat in a flow thru set up sucessfully Tom
Call if you need help !

[HammerDown]

As mentioned above...you CAN'T run a regular T-Stat!
For years now I've run the REX thermostat w/bypass system, functions perfect and keeps a nice temp in the engine.
Too much pressure...never an issue with me as how I have my engine plumbed (thanks to LV-jet boy's tip);)
*1 line-into the engine 2-dump lines out the back. With that setup I never see anymore then 11-12 pounds of pressure, and that includes spikes from the pump, loading/unloading at wide open runs.

[H20MOFO]

I took mine off because I didn't like watching my temp gauge go up then down up,dn,..I could sit there and watch it open and close(on the gauge). So I drilled a couple of holes in the thermostat, and then I was back to adjusting it with the valve again. So I just took it off.

[H20MOFO]

I still haven't picked up a regulator yet. I just had the gate valve, maybe that was my problem? It would march right up to 190* or so then plumett(sp?) to 140* then march right back up, just to fall again. btw it was a rex 4 port with the bypass built in. I have an oil temp gauge this year I'm looking forward to seeing what the oil temp does in relation to the water temp.

[dm2bfree]

Thanks for the info guys! I'm going to look into some of those kits... It's not that it's hard to adjust valve depending on the temp of the water & air, etc.. it's just a pain in the ass to do sometimes :)

[jetboatperformance]

Guage Water temperature in jet drive boats is IMO inaccurate at best and not nearly as critical as oil temps , in a true Marine (eg mercruiser or early Berk pakajet) or an Auto type circulating system the coolant/water is recirculated thru the block and heads etc and "absorbs/carries off" the heat to the radiator or "heat exchanger" and thus the excess heat is disapated ,while the Tsat regulates that process to an almost constant temp. In a jetdrive this is not the case , in a standard 2 port jet set up the water simply passes thru the engine and the water temp is a mis-nomer, passing thru to quickly to take away heat and provide a real temp reading , in the 4 port it (water) does "dwell' shortly until the T-stat or bypass allows it out ,replacing it with cool water from below but it does not circulate, they do create temp fluctuations like Kreg decribed (temp fluctuations create a whole different set of problems . Not saying their Bad (4 ports with Tsats) I sell them just not a fan! We build in our engine clearances for (lake boats)
marine motors and let them run "cold" and monitoring oil temp just my 02 Tom :idea: