Mercury 150 Xl Overheating

[AO]

I Have 2005 Mer. 150xl. Having Problems With It Overheating. I've Changed The Water Pump As Well As The Thermostats And Still Having The Same Problem. The Water Coming Out Of The Pisser Is Steaming Even In Neutral. Does Anyone Have Any Suggestions On What To Try Now?

 

[Windykid]

Re: Mercury 150 Xl Overheating

Not sure if that motor has a popet valve that might be stuck?

 

[Windykid]

Re: Mercury 150 Xl Overheating

Is the tell tale a strong stream? Any obstruction on the intake?

 

[AO]

Re: Mercury 150 Xl Overheating

I'm Getting Ready To Check The Poppet Valve Today. Does Anyone Know What Temp Should Be At Idle.

 

[gss036]

Re: Mercury 150 Xl Overheating

I would be thinking about T's, take them and check in hot water (w/candy Thermostat) to see if they are opening properly at about 143 degrees, or maybe in backwards?? If that is possible? The poppet has no effect if it is hot at idle, the poppet opens by pressure at about 2600-3000 rpm, blockage or T's.
Did you do your own water pump? Maybe the water flow tube is not in properly? I know you don't want to hear, drop the lower unit again, but just have to do it to be sure.

 

[AO]

Re: Mercury 150 Xl Overheating

Well I Put New T's In And The Same Problem Occurs, I Have Been Check It With Only A Garden Hose, When I Put It In The Water The Temp Will Only Get Hot When Running Open, As Soon As I Put It In Neutral The Temp Drops Back Down.

 

[gss036]

Re: Mercury 150 Xl Overheating

On the lower (starboard) right side of the block, there is a cover (looks like an 8) the with 4 small bolts heads. That is the cover for the poppet valve. With your new info, then I would think seriouly about taking a look at the the poppet. If you are careful, you may be able to take the cover off w/o damaging the 2 gaskets. The poppet is spring loaded but will not jump out at you, just work your way around the 4 bolts a little at a time, be especially careful not to strip out the threads, it you have been using the engine in saltwater, soak w/WD-40 or the likes for a while if the feel tight.
Look at the Merc Express site and you get an idea of how the poppet is put together so you won't get mixed up on the sequence of gaskets, grommet, washer and the poppet itself.
Easy access can be gained to the poppet cover by dropping the lower cowling half, just remove the 4 small screws/bolts and tap the cowling lightly and it will drop down, coming loose from the rubber round things.. Nothing to disconnect.

 

[ronnieboy]

Re: Mercury 150 Xl Overheating

hi, had similar problem with 150 xr2, was bad fit in upper water tube seal, i coated the top of the water tube with blue silicone and reinstalled , fixed a 4 year old problem, oh, besure to clean poppet as above, temp should be bout 140 all time, good luck ron

 

[AO]

Re: Mercury 150 Xl Overheating

Well, I Found The Poppet And Took It Off. Found Some Sand In It, But Not Enough To Restrict Any Flow I Don't Think. Wasn't Sure How To Get To The Diaphram. Kinda Looked Like There Was A Screw Going Through Center Of Spring And Diaphram But I Didn't Want To Break. I Put It Back Together And Went For Sea Trial. Water Was Pissing Alot Harder Than Before Which Is A Good Thing. The Only Time It Heated Up Was From 2000-3000 Rpm For About 300 Yards. It Got Up To 200-210 Deg, But As Soon As You Put It On Plane Temp Would Drop To 170-180 Deg. Is It Normal To Get That Hot From 2000-3000 Range?

 

[ronnieboy]

Re: Mercury 150 Xl Overheating

bet your getting exaust gases in the head from the water tube, blue silicone the top of the tube and reinstall , will seal the water in , and exaust out, good luck ron

 

[Galaxy owner]

Re: Mercury 150 Xl Overheating

I had the same problem today.I fixed it by tapping a tapered tool into tube and pulling it out,(pliers will bend it)went to home depot and spent $2.87 cut and wow it took all the overheating problems away!If its not perfectly round I would replace.Now no steam!!!!

 

[szealuss]

Re: Mercury 150 Xl Overheating

WOW, I am having these same issues with a 150 1987. I am going to try this. You mean pull the tube down and silicone it where it meets the block. I would like more info on this if you can. Thanx

 

[CharlieB]

Re: Mercury 150 Xl Overheating

A mid-range cooling issue is NOT caused by the poppet valve failure to open.

It is a LACK of cooling flow thru the powerhead.

Temps should NEVER rise above 145, EVER.

The water pump is sized (oversized) requiring a poppet valve to divert EXCESS cooling water.

Any over temp within a specific RPM range is a usually a cooling flow issue, either the pump is not pumping the volume or the system is leaking it off somewhere.

A common but often overlooked source of leakage and the cause of many strange overheating issues is the gasket between the exhaust adapter and the motor mid-leg. A small break in the gasket allows cooling water to dump straight out the exhaust, without any sign other than a strange over temp situation NOT caused by a faulty water pump, transfer, tube or thermostats.

Lift the powerhead and replace the gaskets underneath it.

 

[fgprent]

Re: Mercury 150 Xl Overheating

could it be a bad head gasket?