temp. for 1992 Mariner 150 Magnum II
 

Haven't had a problem. Just seems really Hot.

Under 3000. . . No problem! When I "Put it Down" temp. goes up to like 190-200 and stays there (doesn't over heat). Just wondering. . . Is that normal? Used it several times and hasn't created any problems.

Been told that "the higher the rpm's, the lower the temp. because there's more water pumping through". And I've also been told that "the higher the rpm's, the higher the temp. because the pistons are working more" (this makes more sense, but I'm not a mechanic. . . YET!)


Thanks

Re: temp. for 1992 Mariner 150 Magnum II
 

Try an extended flushing with a salt removing solution. (Out of water and running in a tank for a while.) It could be that you have enough salt/crud build-up to restrict max flow. Just an idea and a cheap "fix."

You might also add a second run using a mix of H2O and white vinegar. The mild acid will tend to dislodge/ disolve mineral deposits as a result of higher alkaline water sitting in the warter jackets between uses. I shouldn't harm any of the surfaces.

Re: temp. for 1992 Mariner 150 Magnum II
 

sounds to me like you have a poppet valve that isnt completly opening or not opening at proper temp. also if the motor has run hot in the past the wax inside the copper or brass 'cup" on the thermostat wont force the thermostat to open at the proper temp. as the wax gets hot it expands and pushes the tstat open if it has been extremely hot before and some of the wax expands out this would cause the tstat to not completly open or open at a higher temp. just my 2 cents

Re: temp. for 1992 Mariner 150 Magnum II
 

I have a 1991 Merc 150 XR4. Your Magnum II is the gray version of the same motor. My engine temp stays constant around 160 after initial warm up regardless of load.

My XR4 experienced the same problem you describe after the powerhead was rebuilt a couple years ago. Turned out the poppet valve was reinstalled incorrectly. If you have a water pressure gauge, it should read between 10-15 PSI at cruise. If the pressure is way up at cruise, and your temp gauge swings back and forth between 180 at cruise and 120 at idle, I would say it's probably the poppet.
Dave

Re: temp. for 1992 Mariner 150 Magnum II
 

Thank you gentlemen. Gonna make immediate inquiries on both ideas.

So most Defenitely not ok to be running at 190 something degrees at 3500rpm's right?

Re: temp. for 1992 Mariner 150 Magnum II
 

Salt starts to come out of solution at about 160, which is why most marine engines are set up to run cooler than that. If you run hotter than 160F on any raw water cooled engine, you're building up salt deposits!

Re: temp. for 1992 Mariner 150 Magnum II
 

I think 140 is a good target - I would also look at the poppit valve

Re: temp. for 1992 Mariner 150 Magnum II
 

i think my 84 runs a little cooler than that while on plane. then again i dont have t-stats either. altho last time i was out i had perfect water pressure but temp went a little higher than normal. poppet is pretty new too and so is water pump.

Re: temp. for 1992 Mariner 150 Magnum II
 

no t-stats is the worst thing you can do to an engine. although the gauge says cool or normal the engine is saying different. with no t-stats the water has no restriction therefore it is not staying in the engine long enough to "soak" up the heat and remove it from the engine. the water passing the temp sensor is cool because it hasnt been in the block long enough to warm up there for the gauge is showing a inaccurate reading. this will almost always result in a very short engine life or a very expensive repair bill

Re: temp. for 1992 Mariner 150 Magnum II
 

at the yearly maintence time ill put stats in it and take out the restrictors and check it out.

Re: temp. for 1992 Mariner 150 Magnum II
 

WoW!

If 150 should be my running temp. I have a long way to come down. My gauge reads about 135-140 under 3000. When I "Put it down", it goes up to about 190-200 and stays there (never over heats). Weird! Gives me the feeling that it's about to start overheating, but never does. Maybe my temp. gauge (which is new) is not reading correctly.

I am going to change my t-stat (which hasn't been changed in over 5 yrs. And, I'm going to flush it with some "Salt-away" (salt remover).

Question: Is the "poppet valve" different than the T-stat or is it "part of" the T-stat?

Re: temp. for 1992 Mariner 150 Magnum II
 

they are 2 different things. the poppet valve goes on the bottom of the block on the starboard side. its about in the location where your harness connects to the motor. should be less than 15 bucks to buy a new one from boat center. the stats are a few bucks each from boat center. its kind of a pain to do the poppet on your motor because of the lower cowlings. i think you have the same thing as i do. it might be easier to split them at the bottom and get to it.

Re: temp. for 1992 Mariner 150 Magnum II
 

poppet is the relief valve on the bottom right (electronics side)of the block. There are a few different designs.

http://i85.photobucket.com/albums/k6...g/scan0005.jpg

Re: temp. for 1992 Mariner 150 Magnum II
 

I ran a '91 XR4 on my Seafari for six years. I had 135* thermostats installed in place of the original factory stats which actually opened at about 148-150.

I also moniter water pressure constantly. I also had a water temp gauge AND a cylinder head temp gauge for each cylinder head. (Not my idea, actually. The man who remanufactured my motor installed those.)

Result was fairly constant water temp of about 140* while on plane, regardless of how hard I ran it. More than once, I pushed 5200-5500 rpms for more than an hour of constant running, and temp still hung at 140. In contrast, the temp would rise to 145*-150* at idle to 1200 rpms, while maintaining 7-8 lbs of water pressure.

The poppet valve is vital to maintaining proper water pressure, which leads to proper temperatures. Doesn't matter how good your thermostats are if you aren't getting enough water flow to properly cool the engine.

I would do the following, in order:

• Check the Poppet valve for proper installation.
• Check thermostats for proper opening and closing
• Check water pressure. (should be 6lbs minimum to 18 lbs maximum)
• Check/replace water pump impeller and check water pump to inlet tube mating.
• Run motor for 1/2 hour in mild acidic solution in closed system (in a drum or tub) I use 1 gallon of muriatic swimming pool acid in 25 gallons of water.

Let us know.

Re: temp. for 1992 Mariner 150 Magnum II
 

In addition to controling water pressure, the poppet valve also bleeds air from the cooling system. Look at the diagram Bigshrimpin posted. The hose fitting that feeds the poppet valve is at the top of the block where air pockets naturally form when the lower unit takes a gulp of air. Purging air from the system is just as important as controling pressure and flow. Air pockets in a water cooled engine = hot spots. Hot spots create stress when a part of the engine undergoes thermal expansion at a rate different from the part next to it.

Likewise, the T-stats are important for keeping the engine at the correct operating temperature. The rapid heating and cooling that occurs when loading and unloading an engine with no T-stats, and therefore no temperature control, create stress due to repeated, and often uneven, thermal expansion and contraction. That can't be good.

I agree with all of Fr. Frank's recommendations, but I've never run dilute muriatic acid through my motors. The slightly acidic solution I run mine in is the Suwannee River. ;)
Dave

Re: temp. for 1992 Mariner 150 Magnum II
 

That'll work. :D

Seriously. ONLY run an acid solution through your motor for KNOWN salt scale or salt gel build up - NEVER as a preventative measure. I have only done this after opening the water jacket and seeing salt build up present.