Mercruiser 3.7 (165)... Temp guage resovior cap be accurate???

[structural1]

Hi Guys.... the 470 is starting to come together. I still have to chase down the issue with the temp gusgae... works some time and sometimes it doesn't. I saw today a radiator cap by "Mr Gasket" at Autozone that has a Temp guage built in. It was $10 bucks and rated for 18 PSI. I picked it up and thought I would use it as a back up guage on my 3.7 (165). It fits down snug on the resovior. Boat is still in the yard while I chase wiring issues so it is running on the muffs. But the guage reads up to about 155 after a long idle as I would expect.

Question.... is the water in the resovir a good guage of the overall water temp in this engine? The standard guage sensor is in the side of the block and since the resovior water circulates I would think taking water temp in the resoviorit would be pretty darn accurate.

What ya think? Am I wrong?

 

[04fxdwgi]

Re: Mercruiser 3.7 (165)... Temp guage resovior cap be accurate???

Hi Guys.... the 470 is starting to come together. I still have to chase down the issue with the temp gusgae... works some time and sometimes it doesn't. I saw today a radiator cap by "Mr Gasket" at Autozone that has a Temp guage built in. It was $10 bucks and rated for 18 PSI. I picked it up and thought I would use it as a back up guage on my 3.7 (165). It fits down snug on the resovior. Boat is still in the yard while I chase wiring issues so it is running on the muffs. But the guage reads up to about 155 after a long idle as I would expect.

Question.... is the water in the resovir a good guage of the overall water temp in this engine? The standard guage sensor is in the side of the block and since the resovior water circulates I would think taking water temp in the resoviorit would be pretty darn accurate.

What ya think? Am I wrong?

I would say no.

The resevoir tank is on the return water circuit from the block and should be at actual temp where it enters the tank, but unlike a radiator (which the this is designed for) is very large, having the top of radiator at temp and bottom is much cooler after cooling is done, the tank is very small in comparrison and temp in the tank will be consideably cooler than actual engine temp, somewhere between engine temp and raw water temp. I would fix / replace the sender / temp gauge.

 

[Eric 3.7LX Alpha 1]

Re: Mercruiser 3.7 (165)... Temp guage resovior cap be accurate???

I have that same cap on mine. It has been useful when working on the engine. Mine has read a duplicate reading of my dash gauge, however, what he says makes sense, the sender in the block is a better location for a guage and should be in good working order as well.
I will still keep the radiator cap on though.

 

[structural1]

Re: Mercruiser 3.7 (165)... Temp guage resovior cap be accurate???

I have that same cap on mine. It has been useful when working on the engine. Mine has read a duplicate reading of my dash gauge, however, what he says makes sense, the sender in the block is a better location for a guage and should be in good working order as well.
I will still keep the radiator cap on though.

Thanks guys. I'm going to replace the sender and guage this weekend. I only wanted to use the cap as a backup system. Good to know someone else has used this cap and had a good backup experience.

Thanks again

 

[04fxdwgi]

Re: Mercruiser 3.7 (165)... Temp guage resovior cap be accurate???

Thanks guys. I'm going to replace the sender and guage this weekend. I only wanted to use the cap as a backup system. Good to know someone else has used this cap and had a good backup experience.

Thanks again

Backups are good...