overtemp problem

[njo1]

i have a pair of 2003 150 mercs with carburators i have changed water pumps
and thermostats. i still have temps at idle of 140 and crusing at 3500 rpm they both run 180-190 . if i load the boat with fuel and fishing buddies they run even hottor. i have pulled head and water ports look clear and checked presure relief valve looks good to . dont know what to check next HELP please

 

[hkeiner]

Re: overtemp problem

It is sometimes hard to guess correctly at the cause of an overheating problem just by the way the motor runs. The attached troubleshooting guide will give you some ideas as to the some common causes of overheating problems. Of course, the guide would be more helpful if you installed a water pressure gauge on the motors. In my opinion, if rebuilding the water pump does not solve an overheating problem, installing a water pressure gauge is the next thing to do before replacing or disassembling a lot of other parts.

Having said this, I'll take a stab at guessing... I think that it is unlikely for both motors to have the same mechanical failure at the same time. Perhaps both your carbs are jetted too lean causing both motors to run hot or the motors are mounted too high and are sucking air into the water intakes.


http://forums.iboats.com/attachment.php?attachmentid=26806&d=1240515681


http://www.diy-boat.com/index.php?option=com_content&task=view&id=151&Itemid=49

 

[Silvertip]

Re: overtemp problem

A water pressure gauge is certainly a valuable tool but it does not indicate whether or not the engine is cooling properly. It only tells you the water pump is pumping water. That alone is no guarantee there is nothing wrong with the engines. Have these engines always operated like this or is this a new symptom.

 

[j_martin]

Re: overtemp problem

One thing that reliably cooks a V6 merc is overpropping it.

hope it helps
John

 

[njo1]

Re: overtemp problem

thanks for the info . i will try the water presure gage this weekend.
the motors have allways run a little hot. i have had the boat for a bout 2 years. but it seems to be getting hotter dont know if its the engines getting worse or the florida water temp up to 90 now.