Boat Info:1989 Formula 272 SR-1
Motors: t/ 454's basic bolt-ons

Hey guys so, i just got my boat back in the water last weekend and had a little isuue so here's the deal. Last year the impellor broke in the driver's side motor, so this spring I replaced the impellor and put a new Stainless steel thermostat to replace the old brass one. The temp of the new one is 140 degree. So when I put the boat in and took if for a shake down run, the drivers motor kept heating up to 220 and then immediatly dropped to back to 150. So I switched the thermostat out for the same one just another one to eliminate that.Same thing keeps happening 220 heat up back down to 150 repeatedly.The other motor is running at around 110-120 with no overheating.So I removed the thermostat from the driverside motor and just put everything back together so it has no thermostat and it runs perfect, just like the other motor around 110, even wide open running down the river. So it this ok to run without a thermostat? Any adverse affects on the motor?

My 502 with a procharger M1 runs not t-stat . its part of the insatll of the kit . they run there own t-stat housing eliminating one set of hoses and they say to run it without a t-stat.

It is OK to do it but you should get them in. You want the motor to be warmed up before you run it hard. You also want to get the oil hot to cook off the water/moisture in it.

My guess is that if your impeller broke apart that the pieces of it are stuck in the motor some place. Start by looking at the oil coolers then keep working your way at the motor. You should be able to find all the pieces and then the problem should be solved and you can put the T-stats back in.

Just leave them out ,,,unless u have a heater in the boat .LOL

But make shoer u reach a little temp before running WOT !!!

I never had a thermostat in a boat !!!

I don't run one either but I also am running a SC and the t-stat was not recommended. Because of that, I do run an oil t-stat, even in Arizona.

I agree with audiofin that something else is going on. It is always better to find the root cause. His disintegrated impeller theory makes sense.

I dont run them either, but have whipple superchargers. I had a problem with one side doing similar temp climbing, changed out impeller, and found a couple of pieces wedged together partialy blocking the out going hose.

I agrre with a previous post. Start taking apart hoses until you find the other pieces of the broken impeller. The coolers are notorious for catching those pieces. And yes, the last hose you remove will most likely be where the pieces are. I have had this happen to me before. It definitely solved the problem one I located the little rubber culprits.

ok but if i had pieces in the hoses somewhere wouldn't i have the same issue without the t-stat? Also i did get all the pieces out there were still in the housing.

Probably good to go, just give some time to warm up.