I just aquired a Mercruiser 3.7 , have a few questions , take pity on a newby

[Liquid Steel]

Hello,
​I inherited a Wellcraft 190 Classic with the infamous 3.7 I4.
​It sat in a barn for 8 years, It followed me home.
​New fluids, new ignition components , new battery, It starts , runs with muffs , I ordered a water pump kit for the Alpha 1 gen 1 unit.(just as a preemptive strike)
​Finally my question : Where is temp sending unit located on block or head ? My gauge is inoperative. What is a "normal" operating temp range for this engine?
​This is going to be a family tubing , cruiser , beater boat for a couple of years.
Thanks for anything you can tell me .

 

[Bt Doctur]

facing the motor its on your right side in the manifold near the thermostat housing
Never more than 175 ,personally I advise a 140 stat

 

[Benny67]

One think I have learned from these forums is KEEP THAT MOTOR COOL

I have 2 of those evil little thing in my Carver and I always have my eye on the temp gauge. The design of the head makes is susceptible to blowing head gaskets if it overheats.

Mine run around 140F to 150F I believe the oil cooler on them helps immensely in keeping the temp that low.

Treat them right and they are workhorses...but don't ever turn your back on them.

 

[stonyloam]

facing the motor its on your right side in the manifold near the thermostat housing
Never more than 175 ,personally I advise a 140 stat

Nope, a 470 takes a 165 F thermostat. Operating range is 165-200, but you want to keep it below 180. This is a pressurized closed cooling system just like your car. It runs a little warmer than other boat engines, and once up to temperature should stay pretty constant. NEVER let it overheat, change the impeller every other year. Welcome to the 470 club

 

[Benny67]

I run both of mine and I never get the temp above 155F or so....if I'm running a distance MAYBE it reaches 160F It's tough to generally tell how hot it is with an Analog gauge. I'm sure there is a 10% error, if not more. Not to mention paralax error.

I generally never turn the motors over 3700 rpm and I am unsure of what my thermostats are in the engines but like they say...keep em cool and don't abuse them and they will generally treat you well.

From the general reading about these engines it seems a lot of the trouble stems from lack of mechanical knowledge and neglect. Mercuiser would not have made as many as they had if they were garbage.

 

[stonyloam]

Yeah, I'm with Benny on the gauges. Generally they are only accurate to +- 1/2 the smallest increment, so if your gauge has marks 20 degrees apart then you are looking at a 10 degree error. At a reading of 150 your temp could be anywhere from 140 to 160. Best thing to do is run her up to temp and use a Sharpe pen to mark the face of the gauge at that temp and use that as your reference. With the 470, any reading significantly above the mark, find out why and correct it.

 

[Liquid Steel]

Sorry for the late reply !!! Thank you ALL for the sage advice.

 

[kenny nunez]

Look very closely at the way the engine cover seals in relation to the #4 spark plug. Another thing these are famous for is the spark plug rusting to a point the center of the plug blows out leaving the threaded portion in the head.