Automotive vs marine thermostat

[woodguy81]

So haven’t definitively solved my overheating problem but thought about the fact that I used an automotive 160 degree thermostat last spring and ran mostly in salt water with my raw water cooled engine. Is there any difference in the materials used or flow allowed? The motor specs are 2003 5.0 mpi. Serial number 0m670725

 

[Bt Doctur]

engineor drive problem? what other work was performed? how old are manifolds and elbows?

 

[woodguy81]

Replaced the drive last summer and then the upper unit again in the late winter. Manifolds and elbows were off and clear last spring when I rebuilt the top half of the motor. Used an automotive thermostat when i put it all back together though. Just replaced the water impeller although the old one looked new and was only in since July. No leaks in the system that I have found.

 

[Driver50x]

Im just curious why used an automotive thermostat? I was under the impression these engines are designed to use a 140 degree thermostat in order to reduce internal salt buildup.

 

[achris]

Some run 140°, some 160°. Just depends on how the engineer was feeling that day. Either way, a car thermostat isn't made of the right material to be used in a boat, regardless of whether is 140° or 160°. Get a proper MARINE thermostat in. Yes, they cost more, but for a very good reason.

Did you check the engine circ pump?

Chris......

 

[Scott Danforth]

EFI motors run 160, carbed run 140

Unless HX cooled, then 160 on the carb too

 

[TunaFish389]

Here's s good read, not for this engine bit is related. Use a marine termostat just to eliminate that possibility... https://teamtalk.mastercraft.com//showthread.php?p=1476624

 

[woodguy81]

I’ll check the circulation pump as well although that was replaced last spring as well when I was chasing an overheat issue that turned out to be riser gaskets installed backwards. Used the automotive one bc it’s what I could get that day. I’ll order the correct one. Also read that article and the mercury thermostat doesn’t look like the one in that picture. Looks the same as what I got. Maybe different materials.

 

[Bt Doctur]

was the temps checked with a laser, sometimes the sender and/or gauge can go off by over 30 degrees

 

[Scott Danforth]

I’ll check the circulation pump as well although that was replaced last spring as well when I was chasing an overheat issue that turned out to be riser gaskets installed backwards. Used the automotive one bc it’s what I could get that day. I’ll order the correct one. Also read that article and the mercury thermostat doesn’t look like the one in that picture. Looks the same as what I got. Maybe different materials.

the outer casting is identical. however automotive circulating pumps have a cast iron impeller and a steel back cover. marine units have a bronze impeller and a stainless steel back cover.

 

[Lou C]

Agreed the automotive pump is designed for 50/50 water antifreeze mix with corrosion inhibitors and will not last in a raw water application. Neither will the auto thermostat. With marine thermostats I’ve had them get sticky but never had one corrode even in salt water.

 

[woodguy81]

So here’s today’s progress. I’ve changed the impeller in the out drive, and even pulled the thermostat out to see if that was my restriction. No change. I can run in a straight line all day and sit at 165. When I do corners and circles the temp climbs pretty fast. Hit 195 with no thermostat installed doing this. If I drop it back in neutral and let it idle for a few minutes it came back down. I pulled the circulating pump off to check it out. It’s all ok but it’s getting replaced anyway with a marine unit. Also noted that when it’s running all the lines from the thermostat housing are hot but soft. Is this normal or should they be hard to squeeze since they should be full of water. I’m monitoring temps with the VesselView app as well as the dash gauge with similar results on both. Thoughts?

 

[Boater31]

Since it is only happening when turning could it be the hose connecting the bell housing to the gimbal plate, or the plastic tube going into the transom. Did you change any of the rubber parts during the drive change?

 

[woodguy81]

That’s a good thought. Hadn’t considered it and it may have been an issue longer than I know since I normally only run long distances in a straight line offshore and not anywhere near full throttle so I didn’t notice before. I’ll test that theory and report back.