Is a thermostat really necessary?

[kd4uga]

In the process of winterizing the boat I was reminded again that the local boat repair shop did not install a thermostat in my Mercury reman engine when they installed it a couple of years ago. Do I need to put one in? I'm in the south and water temps around here are pretty warm in the summer. Boat runs around 160F and I notice the thermostat is 140F. It's been without one for a couple of years now. Just wondering what more experienced sailors think about this issue.

Here are the Volvo Penta numbers:

Engine - 4.3GL PEFS (4012004849), Outdrive - SX-M 1 79 (4112094763), Transom - SX-MLT (4111633176)

 

[alldodge]

In the process of winterizing the boat I was reminded again that the local boat repair shop did not install a thermostat in my Mercury reman engine when they installed it a couple of years ago. Do I need to put one in? I'm in the south and water temps around here are pretty warm in the summer. Boat runs around 160F and I notice the thermostat is 140F. It's been without one for a couple of years now. Just wondering what more experienced sailors think about this issue.

Here are the Volvo Penta numbers:

Engine - 4.3GL PEFS (4012004849), Outdrive - SX-M 1 79 (4112094763), Transom - SX-MLT (4111633176)

Thermostats are always a good idea. Without a thermostat the block can have hot spots due to air bubbles, those same bubbles can cause issues. As for your engine running at 160 well that's strange even for warm water temps. If your running in fresh water then I would recommend a 160 thermostat, but if your in salt stick with the 140

 

[smassey22180]

Are you sure you don't have a thermostat? Without a thermostat you should not go much more than 100 degrees. My recent 4.3 purchase had a piece of stuck impeller in the housing preventing the boat from reaching 160. Once corrected the engine ran much better. It was always stalling like it was still cold.

 

[kd4uga]

There is no thermostat in there. I just ordered a 160F for it. The interesting thing is the motor runs just fine without it. Thanks guys!

 

[jerryjerry05]

yes!

 

[Scott Danforth]

the thermostat should be up inside the t-stat housing. I would double check. the only way it can run 160F is with a thermostat. otherwise even if you were in the gulf, it would only get to 120F max, and not run correctly

 

[smassey22180]

Random FYI here. The Sierra part is exactly the same as the Volvo one. It has the same part numbers stamped in the metal of the housing. http://www.iboats.com/Thermostat-Kit-Sierra/dm/view_id.485710

 

[BRICH1260]

I bet you have a thermostat in there. Cant imagine getting to 160 without it. Did you look up inside the T-stat housing?

 

[aerobat]

well, depending on the conditions ( load ) and water temperatures it might be your engine runs about 160 without a tstat - it would be the same with a tstat fully opened. nevertheless a tstat provides a quicker warm up of the engine and keeps temps relativly steady in changing load conditions of the engine. without a tstat you engine warms up slowly and if ever under high loads , it also will fluctuate in temperature during load conditions. so put in a tstat , its better for the engine even when it will run good without in warm water.

 

[kd4uga]

After reading these posts, I went out in my pajamas with a flashlight and looked inside the housing. And, there is indeed a thermostat in there. Judging from the looks of it, it's time to replace it. I foolishly thought it would be in the manifold. My replacement came today so I will try to figure out how to remove the old corroded one this weekend.

Thanks again to everyone for the help! And, I will take any tips for getting the old one out!

 

[dypcdiver]

Well done, the stat is held in with and "O" ring just below it. Clean the "O" ring groove of any rust or debris, I use a dremel with a wire brush. BTW your stat should have come with an "O" ring. I usually smear a little waterproof grease in the groove, I've no idea if it helps or not, your choice.

 

[smassey22180]

Getting the old o ring out is strange the first time. Pry it from the outside edge towards the center of the thermostat with a flat blade screw driver. Make a gap. Then work around the edge until it pops up and out. While you have it out check inside for pieces of old impeller. I found one deep within the bypass of the housing.