wezbre Posted January 30, 2011 Share Posted January 30, 2011 Dear fellow Fishraiders, I have a 2004 Mercury 140hp motor that i have had since I purchased my boat new. The hull is a 5.95 Trailcraft Trailblazer plate alloy. Since new I have had continual problems with overheating. I have had the boat back to the supplier so many times that I have lost count. I have the problems when the boat is being pushed along just fast enough to troll skirted lures, from 2000-3000 rpm. As you can imagine, this is frustrating the heck out me. If I reduce the speed to that of an idle, then the temperature returns to below 1/4, otherwise the temperature rises to above 3/4 and nears the red section of the temperature gauge. The response that I get from the supplier and another mechanic is that the temperature, when checked by laser gauge, is at an acceptable level. The second mechanic hasn't been able to wet test the motor to put the motor under load and therefore cant test it appropriately. Any advice on this would be much appreciated. Regards, Wes Link to comment Share on other sites More sharing options...
BFB Posted January 30, 2011 Share Posted January 30, 2011 Hi Wes,I have an 115 E-Tec which operates at a high temperature when trolling. This is normal as the motor is pushing hard without much water flow. So long as it does not go into the red or alarms sound it will be alright. Just like a car engine heating on a long pull but not overheating. Same principle. Link to comment Share on other sites More sharing options...
chrisg Posted January 30, 2011 Share Posted January 30, 2011 (edited) Wes It could be a poppet valve issue. The valve isn't opening early enough to cool the head fully. Ask your mech to replace the diaphram , spring, valve seat and gaskets. If the problem persist you may have one of the problem Mercs that require a simple but non standard modification. Best to try the factory setup first. When was the water pump last serviced? C. Edited January 30, 2011 by chrisg Link to comment Share on other sites More sharing options...
a boat Posted January 31, 2011 Share Posted January 31, 2011 Hi, if the overheat horn is not going off and you are just watching the temp gauge and seeing it rise when you are "pushing" water than that is normal. As the guys have said at low speed and the RPM you mentioned the engine should be hotter than on the plane and the ovrheat horn will come on IF the engine is getting too hot. That said if the original water pump, thermos and poppit valve, it might be wise to service the water pump and cooling system. Cheers, Huey. Link to comment Share on other sites More sharing options...
dunc333 Posted January 31, 2011 Share Posted January 31, 2011 is the alarm sounding???????? Link to comment Share on other sites More sharing options...
abyss Posted January 31, 2011 Share Posted January 31, 2011 Dear fellow Fishraiders, I have a 2004 Mercury 140hp motor that i have had since I purchased my boat new. The hull is a 5.95 Trailcraft Trailblazer plate alloy. Since new I have had continual problems with overheating. I have had the boat back to the supplier so many times that I have lost count. I have the problems when the boat is being pushed along just fast enough to troll skirted lures, from 2000-3000 rpm. As you can imagine, this is frustrating the heck out me. If I reduce the speed to that of an idle, then the temperature returns to below 1/4, otherwise the temperature rises to above 3/4 and nears the red section of the temperature gauge. The response that I get from the supplier and another mechanic is that the temperature, when checked by laser gauge, is at an acceptable level. The second mechanic hasn't been able to wet test the motor to put the motor under load and therefore cant test it appropriately. Any advice on this would be much appreciated. Regards, Wes [ Link to comment Share on other sites More sharing options...
wezbre Posted January 31, 2011 Author Share Posted January 31, 2011 (edited) Hey there Chrisg, Thanks for the reply. I have replaced the factory thermostats with cooler running thermostats and have replaced the water pump and water pump housing three times and replaced the impella a another three times on top of that. You mention a 'poppet valve', is this associated with the thermostat? Appreciate all the feedback Wes Edited January 31, 2011 by Wes Link to comment Share on other sites More sharing options...
wezbre Posted January 31, 2011 Author Share Posted January 31, 2011 I have had the alarm sound only 2 times, and now I guess that I am just concerned that the motor is just running too hot. I will give the motor a run by the weekend and just keep running it to see if the alarm will sound. Thankyou for all the replies as it has put my mind at somewhat at ease. Regards Wes Link to comment Share on other sites More sharing options...
chrisg Posted January 31, 2011 Share Posted January 31, 2011 (edited) Wes At idle speeds the thermostats control the operating tempurature of the motor. At around 2000 rpm the poppet valve begins to open. It acts as a bypass to the thermostats and allows hot water from the heads to dump out through the leg increasing cooling. Its basically a spring loaded plastic plug the thickness of your finger and is located bottom right side of the motor under a cover. If its sticking because the rubber "seat" has swelled, the diaphram is damaged or even the cover gasket has ballooned out to cause a restriction, it will not open properly causing a a hot condition possibly an overheat condition in the 2000rpm range. At idle all seems fine because the thermostats are doing the control, at WOT all seems fine because the pump pressure is overcoming the problem and forcing the valve open. With cooling issues you should always go to the pump first but if your confident in the pump and and thermostats the poppet valve is the next suspect. When doing the pump housing and impeller did you replace the gaskets in particular the one under the stainless plate and did you run a bead of silicon along the 'wall' immediately behind the pump housing? New components might do the job but there are a hand full of Mercs that for some reason just always have this issue as factory standard and need a tweak. All this said be wary you can be chasing something that might just be ordinary operating condition but I suppose you have gone so far in chasing this thru, the poppet is the logical next step and is a relatively inexpensive job for peace of mind. Cheers C. Edited January 31, 2011 by chrisg Link to comment Share on other sites More sharing options...
Little Hooker Posted February 2, 2011 Share Posted February 2, 2011 I had a over heating problem once due to the impeller blades breaking off and worked it self into the motor and blocking the water ports. Took it to the mechanics nurmerous times for them to tell me it didnt have a problem so took it in my own hands and started to pull off the cooling jacket off and low and behold i found half of my impellor inside my motor. My 2cents Link to comment Share on other sites More sharing options...
wezbre Posted April 11, 2014 Author Share Posted April 11, 2014 I want to thank everyone for the replies and the comments trying to rectify this problem. As stated, I have had this issue since new and the boat is now 10 years old. I was told by the marine place that sold me the boat new that there was no issue with heating and that they had actually replaced the water pum, ( at a cost of $500, 'Warranty?, the water pump doesn't fall under warranty' Well last weekend, being 29th April, 2014, I chose to buy a water pump, impella kit, and replaced the water pump and housing myself. To my dismay, and disgust, I found the bottom gasket of the water pump housing, had a tear in it. It was therefore replaced and after water testing that day, the temperature gauge did not get above 1/4 warm. All this time, a $3 gasket was the reason for this temp issue. I was not able to use this boat for its intended purpose because I believed what I was told by the marine place that sold me the boat and motor. They are yet to hear from me about this as my anger has yet to calm. They will hear from me in the coming weeks. I wish I could name and shame this place but am not able to as I don't wish for repercussions from this site. In this time, I had lost interest in using the boat, taking my family out in it, and after consulting with mechanic authorised to Solve this issue, was not able to for fear of the unknown costs involved. I have a renewed passion for fishing, have taken my youngest son last week into Botany, and have has the pleasure of seeing him hooked up to decent sized Kingfish on several occasions. We are about to join the local fishing club in Sans Souci and plan on making up for lost time. Thanks again all who took the time to try to help.. Regards Wes Link to comment Share on other sites More sharing options...
Blood Knot Posted April 11, 2014 Share Posted April 11, 2014 Bad story - great ending Understand your anger & frustration, good news that you have found the problem and can now renew your passion for fishing/boating. Cheers Blood Knot Link to comment Share on other sites More sharing options...
namese Posted April 12, 2014 Share Posted April 12, 2014 I have a 150HP Optimax 2008 and I have gone through frustration at times myself. it's normal for the temp gauge to sit between 65 to 72 degree Celsius during idle and trolling to about 1000RPM. anything after that the poppet value opens up and the temp should drop to about 42 degrees Link to comment Share on other sites More sharing options...
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