over heating

[Bob Dowdy]

I'm running a Mariner 1995 Carb/v6.At very low RPM,runs cool-When I crankit up to 2000/3000 she pegs the red line & alarm goes off.I have put a themometer on the return and it registers 137 degrees.Also worth mentioning is when I run at 3500 & up she runs cool.Planning on changing water pump and impeller in the spring--any ideas on checking anything else????????

 

[Reel Appeal]

Re: over heating

Bob,<br /> Most likely is that water pump impeller.Check the thermostats for corrosion.Replace any suspect part.Also check the intake screen on the lower unit for mis-alignment or clogging.Do you have a dash mounted water pressure guage installed?Is the water stream strong at idle?It should get stronger as rpm's increase.Are you getting proper lubrication(blue smoke)?Good luck.Post back....

 

[BillP]

Re: over heating

Assuming the water passages are not blocked I'd guess your sensor is bad. I think 137 is ok but don't know your engines specs. Most I've seen run around 140. <br /><br />Reading the telltale for water pressure only shows when the impeller is worn really bad. When it is running borderline the telltale will still look ok even when the pressure is down. I just went though this same situation with a 96 Mariner 50 4 stroke.

 

[KIWI MERCMAN]

Re: over heating

Bob<br />Themostats in this model are 143 deg's, so I would be checking that sender first. The system is disigned to run hot at idle and to cool off above the 2200 rpm approx. I would also check your poppet valve as well, if it is leaking your pressure will be down at idle and this also can increase your temp.Your looking for around 10 psi + or - 2 at idle and up to 15 to 20 psi at WOT depending on your system. If you haven't replaced your impeller for a couple of years then it's a must. Good cooling, fuel and oil is what keeps these alive.<br /><br />Kiwi

 

[Bob Dowdy]

Re: over heating

Thanks for all the helpful replys I think I'm on the right track when I change my water pump and impeller.<br /> Tight Lines Bob