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Mercruiser 3.0 Exhaust Manifold too hot????

R

redfiveshoe

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I have a 2003 Searay 176 with a Mercruiser 3.0 . I have been concerned that it is running too hot. While on the lake , i took a temp gun and shot different parts of the motor. I got 170-180 everywhere except for the exhaust manifold. It was 200-205 up front and 195-200 near the back. Should i be concerned about this?
The boat seems to run around 175 anyway, according to the gauge. I recently had alot replaced thinking that it was running too hot. The thermostat, gauge, water recirulation pump, are all new. I also had it checked for any leaks and everything was good. The impeller has less than 30 hours on it (1.5 years) and the boat holds steady at 175, it doesn't rise at higher rpms. If it was the impeller, wouldnt the temp be rising at higher rpms?

Is the motor temp a problem? Manifold temp a problem? IF so, what could it be?
 
First, did you put a marine 140 degree thermostat in it as required? Or accidently a 180 degree car thermostat?
 
I don't think you have anything wrong with it. First off, I have a very similar boat and my gauge runs about 175. I suppose if the thermostat is a 140 you would expect 140. However, depends where the sender is located. The combustion process is very hot so of course, parts of the engine where the water jackets is not close to the surface will be hotter that 140. At the exhaust riser I would expect 195 -210. The exhaust gas is the hottest part, just like in a car. Stop, STOP putting in new parts. Nothing is most likely wrong. As long as the motor is running well don't over-think it. That or bring it to an experienced Mercruiser mechanic.
 
I disagree, When was the drive serviced last with a new water pump?
When was the riser replaced last 11 years is way overdue.
How long have you had the boat?
With those temps you will pop a head gasket
 
how do you figure. Cars all run in that range. I am no expert on boats but 175 on a car is typical. BTW, he mentioned the water pump was changed 1 1/2 year ago.
 
is this motor RWC or FWC . 1 1/2 years means he`s due for a pump service
RWC ,brass therm 143, SS therm is 160
FWC lists 143

Boasts don't run on the highway
 
It is FWC. I just replaced the impeller about three weeks ago and nothing has changed. The thermostat was replaced by a local certified boat mechanic, so I can only assume that it is correct. The water recirculation pump was replaced earlier this year.
I spoke with another boat mechanic about it and he felt the same way that Phillip feels. He said not to worry about it unless the temp rises. Just accept that 170-175 is normal for this boat.
 
Here is the spec, Note the serial number break down on the lower image. It shows what thermostat for what serial number. Now this is from a 1999 printing of the service manual so keep that in mind.
 
now that we know its a FWC motor
UntitledT3_zps2eb85c25.jpg
 
your right that boats don't run on the highway but then again, why should that matter. Your basically taking an automotive engine that does run on the highway at 180 degrees with no issues. So why shouldn['t it run just as well on the water at that temperature? The motor was originally designed for those temps. Don't worry about it, you are fine.
 
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