Overheating 83 150 merc v6

[Checkmate Perry]

I recently got a 83 150 v6 merc with an overheating issue. I replaced the water pump, missing thermostats & new poppet valve. Temp guage reads 170 180 on the hose.Water out the pee hole is hot,water out the prop is only warm..Water psi is 4-5 at idle,9 10 at fast idle..I also removed heads to check for salt build up. All is clear! How accurate is that temp sender that doesnt touch water? Temp gun reads about same as temp guage?

 

[Chris1956]

Re: Overheating 83 150 merc v6

Perry, Is it getting all the water it wants while running on the hose? I need to use full water flow on my '93 V6, and it will take more than that.

You might try it in the lake. Make sure the water intakes are clear, since we can get a buildup of barnacles her in the salty water. On my '93, only water that passes thru the thermostats goes out the telltale, so it is always hot. Most water goes out the prop and gratings. Your water pressure sounds OK.

 

[j_martin]

Re: Overheating 83 150 merc v6

Should be uncomfortable from the pee hole, but shouldn't be hot enough to actually burn you, unless you stay in it for minutes.

T-stats could be partly plugged, or installed upside down, wrong part, or just plain shot.

I would be suspicious of the temp gauge. It'd be worth checking before you get yer shorts all in a knot.

hope it helps
John

 

[gss036]

Re: Overheating 83 150 merc v6

The t-stats should 143 degress to start opening. That is usually a little hotter than hot water out of you kitchen tap. If the gun is giving you the same reading, then you may need to start checking for obstruction, but "first" do the lake test as suggested. Run it up to about 3000+ rpm and the poppet should open allowing more water flow through the block and it shoul cool down 20-30 degrees.

 

[Checkmate Perry]

Re: Overheating 83 150 merc v6

Thanks for the reply Chris..I will run it in the bay the first nice day we have here in N.J. The system seems simple but i wasnt sure if I overlooked something not having an outboard boat for some time. TNX Agn..Perry

 

[Checkmate Perry]

Re: Overheating 83 150 merc v6

Comander Thanks for your help.. T stats are new and measure about 145 on gun around the housing.. Ill look for that drop in temp when the poppet opens,now that I know what to look for.. TNX Agn. Perry

 

[Checkmate Perry]

Re: Overheating 83 150 merc v6

Chief, Thanks for the reply..I wasnt expecting a big difference in the temp between the two locations. The t stats are new as the previous owner had them removed.. This is where i started to fix this problem..A new water pump and poppet valve. I wanted to be sure I didnt overlook something.. TNX Agn. Perry

 

[Texasmark]

Re: Overheating 83 150 merc v6

The block fills with water and at the top is a rt angle hose barb and 3/8" hose that goes below the block. Any water coming from here is not temp controlled. So it will mix with stat output water and be cooler. Also, the alum mid section can provide some cooling (heat radiation) of any water going down to the prop that you won't get from your pee hose.

140F is the Normal setting for most domestic water heaters for a general idea of the opening temp of the stats.

Mark

 

[CharlieB]

Re: Overheating 83 150 merc v6

Couple of very important pieces of information are still missing.

I gather that the engine is new to you as you mentioned the previous owner had left the t-stats out.

Did you buy just the motor or the boat/motor package?

What is WOT RPM?

What prop?

If this combination 'lugs' the motor the temps will rise.

Test and re-post results in order for us to make better informed decisions on advise.

 

[j_martin]

Re: Overheating 83 150 merc v6

Like Charlie said. That motor wanna be free. If you hold it under 5 grand at wot, things gonna get hot, (wiring, paint, pistons, etc) . You almost can't hurt a merc V6 underpropping ('cept the oiler maybe).

jmho
John

 

[Texasmark]

Re: Overheating 83 150 merc v6

Just a tidbit here. If the engine was run for any length of time without the stats, I'd suspect damage to the top cylinder/piston on the Starboard side (whatever cylinder # that is). The starboard cylinder bank is physically located higher than the port bank and if the port stat is removed, at lower speeds, water can run out of that hole and not allow the block to fill, hence allowing that starboard cylinder to be partially without cooling water.

Mark