Another high temp question

[jclint08]

Hope all are enjoying this 4th of July!

Engine temp alarm pegged out (220) this morning which caused alarm to constantly beep. Immediately shut down & sat for 15 minutes or so until temp gauge read 180. After spending another 5 minutes to get it to crank, I headed for the boat ramp at about half WOT (RPM gauge decided to stop working this morning as well). Within minutes, I was 220 with alarm going off again. Shut it down again and used trolling motor rest of the way.

At idle, water pressure was around 3#. Up on plane when the alarm went off, my water pressure was around 10#. Tell-tale stream was shooting out entire time.

Get it home this afternoon on muffs, tell-tale takes roughly 20-30 seconds to shoot out after cranking up (which it always has) but the tell-tale water is almost scalding hot. Temp only reached around 160 which I assume because was only fired up for 60 second or so before I shut off.

Temp reached 200 last weekend as I was heading in to load up. Had just fished over some underwater vegetation/ moss. Even though my outboard was up as I trolled through, I could have possibly sucked in something when I headed for the ramp. If so, where would I even start to take things apart to check? Both thermostats? A water "filter"? The impeller? Poppet valve?

I know there are several threads regarding this issue, just hoping someone has come across the exact situation with a close enough outboard type to possibly help me out. It is a 1986 Mercury 150 HP Blackmax V6, 2-stroke.

 

[gm280]

Re: Another high temp question

If you think you could have sucked up some trash (vegetation or whatever) I would remove the LU and check the impellor (and replace it at that time as well either way) and also check the thermostat if you have one. Trash could be blocking that as well. Then I would blow air through the entire cooling system before reinstalling everything back together... JMHO!

 

[jigmister]

Re: Another high temp question

water pressure is low compared to my 175HP 1986 merc. I get closer to 20 on plane.

Impeller sounds like its shot to me. I fish in heave vegetation all the time without much problem. I think you have a bad impeller.

 

[jclint08]

Re: Another high temp question

Thanks fellas. From what I've read, replacing the impeller, as well as the thermostats should not be too hard a task for a shade tree mechanic as myself. Now I am in search of a reputable, online marine store where I could order all of these cooling system parts. Impeller or entire water pump kit, thermostats, replacement hoses to the thermostats, temperature sensor & poppet valve are the parts I should probably replace why I have it in my garage.

 

[jigmister]

Re: Another high temp question

pay the extra bucks and get mercury parts. I went with an aftermarket impeller and housing once and the parts were junk.. So much so that I did not even use them.

 

[joed]

Re: Another high temp question

The site you are at here (iboats) sells everything you need.

 

[Faztbullet]

Re: Another high temp question

Your year motor should have 5-8 psi at idle and 18+ at wot. As posted earlier impeller sounds shot.

 

[jclint08]

Re: Another high temp question

Thanks again. Ordered a new water pump kit & thermostat kit this morning.

Would one thing/problem cause the tell-tale water stream to be close to scalding hot? Just curious.
Hopefully a new impellar will help the water shoot out the hose quicker than the 20-30 seconds it takes now.

 

[jigmister]

Re: Another high temp question

It will take some time for the tell tale to begin shooting out because the thermostat must first warm up and open.
Anything that reduces the water flow will cause scalding hot water from tell tale. Since you have it apart new impeller and T stat are good to replace. impeller is recommend every second season. flush out all passages you can when its out.
should fix yer problem.
Remember running an impeller dry for a minute will destory it.

 

[jclint08]

Re: Another high temp question

OK here's an update. Last night, installed (2) new thermostats and gaskets, new water pump kit & new water line hoses. Even put bead of high-temp RTV silicone on back side of water pump housing (my mechanic recommended this to help rule out any exhaust going into water pump causing previous high water temp problem.)
So after letting it all sit overnight, dropped outboard into tote of water, fired up and...

1) still takes 20-30 seconds for tell-tale to shoot water out after cranking.
2) tell-tale now has a very weak stream where before with high temp alarm going off, it was stronger.
3) water temp coming out of tell-tale still seems to be almost scalding hot. Not sure though if it has always been that way.
4) water pressure is still 3-5# at idle.
5) water temp did stay below 160, with no alarm, at least for the 3-5 minutes I had her cranked.

Old impeller did have a few scratches/cuts on every blade perhaps from running dry at some point. It was completely intact though, thank goodness. Old paper gaskets of old impellar did have parts missing, from I assume age or running too hot. Not sure.

Have ordered new poppet valve parts, even though the one in there now has no visual defects that I can see.
Anyone had these same symptoms after new cooling system parts installed?