Mercury 89' 175 black max always running warm

[prosise]

Hello all,<br /><br />I have an 89' 175 mercury, i disabled the oil injection in 96', engine runs great but has always ran warm. I religously change the impeller. I have pulled the water pump & will replace in a few days. I have read about checking the thermostat & will probably replace as well. My question is: i have read numerous threads about this engine running on the warm side. I would like to be able to not always have the idea in the back of my mind about running too hot. I could never pull another boat with a tow line due to the engine temp. If i plane out it cools down & is normal, but if I tried to stay at just over a plane it will start to run hot. THe prop is running a bit strong, i think a 23 deg quicksilver. Any sugg would be greatly appreciated. ALso: the tube that plumbs into the top of the water pump seems to be a bit boogered up, is this something that is easily replacable? I can see it is free of abstructions all the way up to the engine. I just do not want to loose any pressure to the engine at the spot where it connects to the pump..<br /><br />Prosise<br />bprosise1@charter.net

 

[sharkcat]

Re: Mercury 89' 175 black max always running warm

Of course it runs warm MERCS ARE HOT in case you didnt know .You should be able to buy a waterpump repair kit that will supply you with an impeller ,gaskets, base plate & water pipe connection hose.Change thermostat & poppet valve if fitted,clean out waterways as much as you can.Give it a tune up & you should be good to go have fun What WOT RPM are you getting? Your manual will tell you the recommended RPM range you should be running at the high end of this lugging a 2 stroke is bad news..but good if you sell spare parts.A 1 inch drop in pitch will raise your WOT RPM approx.200rpm. Hope this helps

 

[bshores]

Re: Mercury 89' 175 black max always running warm

I have the exact same concerns with my 1989 175hp Mariner/Merc, Prosise. Temp rises to 150-170 degrees when idling for extended periods of time, but shoots right down once on plane. However, every time I touch the block after running, it is really hot(I can barely hold my hand on it). It doesn't sit easily with me, but from what I keep hearing, Mercs run hot.

 

[dakk1]

Re: Mercury 89' 175 black max always running warm

prosise<br /><br />I believe Sharkcat is right about Mercs running on the warm side. I have the '85 Merc 150 Black Max and it seems to run a little warm. I can lay my hand on the head for 3 or 4 sec but thats about it. Also local Merc mechanic told me the #1 cylinder on the top right runs hotter than the others. I don't know why that is but it seems to be hotter than the other bank.

 

[AndyL]

Re: Mercury 89' 175 black max always running warm

My belief is that these engines do run hot at low RPM but should not go into ther red on the temp guage. Max about 180 degrees. The water pressure in the block is regulated by the poppet valve and should this be leaking you will lose water pressure especially at idle / low rpm hence rising temperature. At speed there is enough forced injection of water to keep temps down. The top cylinder right hand side is the highest and hence will experience the hottest temps, that is why a sender is positioned there, The one on the other side of the V is wired to the alarm side I believe. High temp at idling if the stats and impeller are good would lead me to think that the poppet valve is failing. either replace it or get it looked at professionally as it is not a big job to do compared to a failure due to over heat. Good luck but don't ignore abnormally high temps.<br /><br />Andy