Raw water cooling

[rtrippleclick]

Can someone please explain why a raw water cooled motor with a 140deg thermostat, can heat up to 160-170. My thinking is, with a whole lake to cool the motor, it should stay at 140 deg. at all times. Why is that.<br />Thanks,<br />Bob

 

[tommays]

Re: Raw water cooling

the stat starts to open at 140 it may not open all the way till 150 or more<br /><br />the temp guage is not that exact from boat to boat<br /><br />there could be a problem water flow on you boat my 3.0 never runs above 155 unless i pick up ell grass or something gets pumped in to the stat and blocks the flow<br /><br />if the motor is to lean or timeing is out it can make the motor hot<br /><br />if the prop is to big the motor can run hot<br /><br />tommays

 

[Dunaruna]

Re: Raw water cooling

A motor with a 140 deg thermostat will typically run at about 160 deg. The thermostat opens slowly and should cycle through the range - its normal.<br /><br />The temp of the raw water intake will vary this slightly, same as the air temp going through a cars radiator.<br /><br />Aldo

 

[crazy charlie]

Re: Raw water cooling

Thats not how it works bobby boy.If you only idle and the intake water supply is always the same temp then you will have about 145 degrees steady HOWEVER as you increase rpms and load passengers and gear into the boat and put more of a demand on it to work harder and the lake water gets warmer as the summer goes on ----all of these variables will cause the temp to increase.Charlie

 

[Dunaruna]

Re: Raw water cooling

A thermostat that fully opens instantly and stays fully open. O/K, I bow to the Lt. Commander and chalk it up to experience. My bad <br /><br />Aldo

 

[Scaaty]

Re: Raw water cooling

You could try junking the stat, and get a new one and a candy thermometer and check it in a pan on the stove (check your old one too).<br /> My 140 stat on a 350 5000lb runs 140 regardless of varibles.

 

[rtrippleclick]

Re: Raw water cooling

Thanks for the reply guy's. Is 160 to 170deg. ok?<br />I have a 1 year old impeller, thermostat and sending unit.The temp stays at 160-170 at idle or wot. I changed the impeller because it was 8 yrs. old. It always ran around 140 to 145. After the new impeller, it bumped up to 160-165. I changed out the sending unit. Still 160 to 165 So I changed out the stat. Same thing. Am I ok with the new temps?<br />Thanks,<br />Bob

 

[sealyons]

Re: Raw water cooling

You may want to check your manifolds and risers. They get pretty rusty and gunked up after a few years, restricting the water flow.

 

[rtrippleclick]

Re: Raw water cooling

Sealyons, I did check it (3.0l) I also replaced the exh.shutter while I was in there.Could the design of a aftermarket impeller change the temp. This started when I changed the impeler.<br />Thanks,<br />Bob

 

[kopy kat]

Re: Raw water cooling

found an interesting article about impellers:<br /><br /> http://www.marinemechanic.com/site/page159.html <br /><br />might explain some of the differences we are seeing.