Over Heat @ low rpms cool at high

[nofishtoday]

I'm new to this board so I did a search before I posted and I have the exact problem ,,if it IS?? <br />In this other post I feel that is wasn't really answered compleatly or followed up by the poster<br /><br />Don Schmidt Wrote<br /><br />I have a '92 200 Hp. Mercury outboard that the water temp. gage indicates above mid-range temp (if it were a gas gage,it would be the 3/4 full mark)occassionally. The water pump was replaced last season as an attempt to fix this problem?? Is this really a near overheating problem,or an incorrect gage calibration?<br />The temp. settles back down to "normal" if I run for a few minutes at "cruising" speed (more water flow). Thanks<br /><br />

FOULED PLUG<br />I checked out a Quicksilver gauge at the local Merc shop. Lowest peg=100 degrees. Highest=240. 3/4 would be around 170 to 180.<br />Did the thermostat get replaced at the same time as the impeller

I did the impeller and both the thermostats <br />Thanks for any help<br />Nofishtoday<br /><br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=29;t=002358

 

[The Marine Doctor]

Re: Over Heat @ low rpms cool at high

Have a look at the poppet valve. Could be partially blocked.<br /><br />TMD

 

[nofishtoday]

Re: Over Heat @ low rpms cool at high

The Marine Doctor <br />Someone has mentioned this to me how would I go about clearing it <br />I was told its starboard side under the cowl <br />but how do I clear it or do I dismantle

 

[CU2NITE]

Re: Over Heat @ low rpms cool at high

What kind of motor is it? How hot are you running at full and at idle? The poppet has a diaphram that could also be bad(very easy to change) to check for obstruction in the poppet just remove and look in the hole. Also about 3/4 on a 240 gage there is an 8 and a 9. The 8 is a hair before the 3/4 mark and that is 176 degrees and the 9 is just after and that is 194 degrees. I believe the horn will sound at 210. It seems they could have made it a bit easyer to understand, but that's the deal. Good luck<br />CU<br /><br />----------------<br /><br />RUNNING THE MOTOR WHILE LISTENING TO THE HORN WILL MAKE YOU MORN!!

 

[The Marine Doctor]

Re: Over Heat @ low rpms cool at high

Poppet valve is located on the bottom of the Starboard side...just prior to where the crankcase assembles.<br /><br />It kinda looks like 2 round disks hooked together. or Like an 8<br /><br />TMD

 

[nofishtoday]

Re: Over Heat @ low rpms cool at high

CU2NITE <br /><br />200 merc (1992) I started out with an impeller no help....... then installed 2 new thermostats( which where rotted) I took it out yesterday ran great till I lowered down the rpms the meter went right up to the 3/4 line I re opened the throttle and down came the temp <br />I ran about 15 miles @4800 rpms and no heat as soon as I slowed it down to dock,<br />up comes the heat <br /><br /> <br />Tommorow I will check that gage and look into the (poppet valve)

 

[CU2NITE]

Re: Over Heat @ low rpms cool at high

If you run it on ears in the drive does your motor get hot then? IF it does put your fingers on the top of the head and see if it's to hot to touch. Just want to make sure you are overheating, you could just have a bad sensor. Your sensor is on the passenger side on the back of the motor under the top spark plug hole. Some guys make the mistake of tightening these to much causing them to get damaged and not work correctly. Good luck.<br />CU<br /><br />-------------------<br />RUNNING THE MOTOR WHILE LISTENING TO THE HORN WILL MAKE YOU MORN!!

 

[gss036]

Re: Over Heat @ low rpms cool at high

Your thermostats should be opening up at 136 or 146 degrees, can't remember which one. That is about the same range that most hot water tanks are set on from the factory. You should be able to hold you hand under the flow. Take a candy therometer and a container, run on the muffs w/hose and see what the temperature is reading. That will give you an idea if you are really overheating. Most guages tend to read low though. My guage on my 200 hardly ever gets over 110. My mechanic changed the impeller and checked it a couple weeks ago and everything was ok. I had told him about the guage and that was his response.