Mercury 150 XR2

[chadbenton]

Hi, new member with lots of questions, but I will limit them to one at a time. My merc. seems to overheat at high rpm's. At full throttle the temp guage will reach up into the low 200, but will drop just as soon as rpm is dropped. Have installed complete water pump set and thermostat. Have heard not to trust guages and I should install a water pressur guage. The water flow out of the **** tube at idle fluctuates, not a steady stream that I was used to with my Evenrudes. Any ideas

 

[Laddies]

Re: Mercury 150 XR2

The unsteady stream at idle is the thermostats opening and closeing you could have a bad guage ot sender but if the popit valve is sticking it will cause the engine to overheat a high speed

 

[chadbenton]

Re: Mercury 150 XR2

Where is the poppet valve loacted on a merc. The opposite head from the thermostat...Thanks

 

[Laddies]

Re: Mercury 150 XR2

Chad, first there are 2 thermostats 1 on each head, the popit valve is on the starboard side of the block down low, it is shaped like a figure 8 with a large and a small end held on with 4 bolts. The function of the valve is to open and dump water at high speed to better cool the block

 

[j_martin]

Re: Mercury 150 XR2

That's where a pressure gauge is useful. If the poppit valve is sticking, the pressure and temperature will be high. If there is water delivery problems, the pressure will be low, and the temp high.

Water pressure is taken from the top of the block between the banks.

hope it helps
John

 

[chadbenton]

Re: Mercury 150 XR2

Thanks, you guys just answered a lot of questions regarding this problem and now I have a good starting point. I replaced one thermostat last year, but did not realize that there was one in each head, even under parts breakdowns it only shows one thermostat..

 

[chadbenton]

Re: Mercury 150 XR2

I think I have found the problem with my temp. guage showing a high temp. Today, I pulled the temp. sender to inspect and ohm... The sender itself is seating too deep and is bottoming out on the head, it is very apparent by the rotational marks on the sender and the head. Correct me if I am wrong. But, the heat transfer from the head will give a higher reading that just from the water. Anyone ever seen this before...

 

[crazyedd]

Re: Mercury 150 XR2

Does anyone know how this problem was repaired? I have the same engine which runs hot at WOT but immediately cool at less than 4500 RPM's. Installed is new t'stats, new poppet valve, new impeller, new sender and gauge. What is the proper running temperature?

 

[j_martin]

Re: Mercury 150 XR2

Does anyone know how this problem was repaired? I have the same engine which runs hot at WOT but immediately cool at less than 4500 RPM's. Installed is new t'stats, new poppet valve, new impeller, new sender and gauge. What is the proper running temperature?

What pressure are you running at WOT. I ran over an old rotten log once. Overheated at speed till I found and evicted all the wood chips from the cooling system, heads, exhaust plate, etc.

If you're running a prop that has good dig at the surface, like a high five, you could be pulling your water pickup slots out of the lake at full speed and trim, also. Pressure gauge shows it well.

hope it helps
John