Mercury XR2 150 high water pressure

[AFR Engines]

Hello all. I have a Mercury XR2 150 that the water pressure is high and going threw the lake it gets hot. Engine has 14-15 lbs of water pressure at idle and 20-25 at wot. It takes about a min or so and the heat gauge starts reading hot. If you slow down it cools right back off. I have replaced both thermostats,complete poppet valve, water pump and housing,pressure gauge, I have removed heads,diverter,power head,exhaust plate,replaced all gaskets with new,and checked all coolant passages in the engine. I have used a bore scope and blew threw every water passage I can find and nothing has been plugged up. I have ran out of ideas and need help if you have ran into this before. Thanks

 

[Dukedog]

did you split tha exhaust adapter plates, replace that gasket?.. if so i'd be scratchin' my head also.. only thing I know of that causes "high" pressure like your describin' is like said, a restriction somewhere...

 

[Faztbullet]

Does the alarm go off???? Heat gauges can cause you to chase ghosts...

 

[AFR Engines]

Duke dog yes sir I split both plates on the bottom of the power head and blew threw all the holes. Used water to make sure everything was open and installed new gaskets on both sides of the plate. Also used a borescope up int the water jackets while power head was off. Faztbullet the alarm doesn’t work but I have tested the gauge by grounding it out and the gauge goes full swing. With the high water pressure and getting hot I believe it is reading correct. Thanks for the reply’s guys.

 

[dingbat]

Quite often issues like this turn out to be things that where overlooked or assumed during the troubleshooting process.

You changed the pressure gauge. Did you check that the tube running to the gauge isn’t water logged?

Did the problem exist before you changed the water pump?

Have you confirmed the restriction isn’t in the lower leg?

Checking the gauge is “full scale” is only part of the test. Gauges can have different input requirements. Are you sure the gauge and sensor are a matched pair?

Have you checked the output (accuracy) of the temp sensor?

What happens if you remove the poppit assembly?

 

[jimmbo]

How high is the engine mounted on the transom and/or how high are your trimming the engine at speed? If the engine is not getting enough water at speed and the block is not filling up fully, the water, not circulating properly will boil, and the resulting Steam will cause a High Pressure reading on the gauge

 

[AFR Engines]

Dingbat I have replaced the line to the pressure gauge and also ran a different gauge right off the engine. I have owned this boat 10 years and it would run 3-4 lbs at idle on muffs or in the lake and 15 or so at 6000 rpm. It Would run about half way up on the temp gauge when the water pressure was normal. Yes I have had the lower unit off several times and tried different water pumps and housings with not much difference in pressure.

 

[AFR Engines]

Jimmbo on muffs the pressure spikes on start up way before any temp is in the engine.

 

[Faztbullet]

You got a poppet problem

 

[AFR Engines]

Faztbullet you think so? I have replaced the complete assembly and it didn’t change anything. I took it back apart to make sure all was ok and everything is correct according to my mercury service manual. What are you thinking? Thanks for the replays all

 

[Dukedog]

tha only time I've seen 'bout tha same when all was exhausted (like sounds in your case) chasin' same problem was tha grommet in tha exhaust adapter for water tube was messed up and coverin' part of tha inlet... looked fine jus lookin' at it but when tube was installed it would partially "fold over" for lack of better description of what was happenin'... it did give bogus pressure readings but temp was more of our concerns.. donno?

 

[AFR Engines]

thanks for the ideas Dukedog. I looked at that when the adaptor plate was off but can revisit this as it is driving me crazy.

 

[Dukedog]

it wasn't noticeable jus lookin' at it.. one of tha kids decided to poke tha copper in it layin' on tha bench ta recheck tha fit .. gl with it... hope ya find it and if so be sure ta let us know...

 

[AFR Engines]

Had time tonight to take everything apart. Pulled poppet and couldn’t find anything. Pulled power head again. All ports are open. Ran wire and blew air threw all ports. Also hooked a vacuum to several places. Can’t find anything plugged. I am to the point of giving up.

 

[Dukedog]

only other thing I can think of but it depends on when this started.. did it start after you pulled ph and split tha adapter plates or did it start before you did anything to it.. reason I ask is there two different gaskets that fit "between tha two adapter pieces.. that's all I got.. you really outta get tha "buzzer" workin' from tha port head.. i'm a real believer with that warnin'.. jmo

one other thing after a "re-read".. what do mean by "diverter"?

 

[AFR Engines]

dukedog it started one spring out of the blue, I was talking about the exhaust diverter in the center of the engine under the coil packs.

 

[Dukedog]

that's what I figured.. might try another water pump kit?.. have seen some strange things with a new one before..

"divider".. figured that was whatcha were talkin' 'bout.. diverter is something used in tha high performance blocks but installed in tha production blocks by some for added coolin' effect...

hope ya find problem.. if ya do please post it up.. i'm really perplexed by it...

 

[AFR Engines]

ya I wasn't sure the exact name for it. I did try a new pump before I posted and it didn't change anything. Thanks for all your help and if you think of something let me know. I left it apart last night incase someone had an idea.

 

[AFR Engines]

it seems crazy that there are so many people with this problem on here and i have yet to find someone say they got it fixed and what it was.

 

[sam am I]

So perhaps the restriction/s is down in the block (left and/or right side/s) in some dark corner?............Truly shouldn't be too difficult to figure out.

Remove poppet and stats, if too high of H2O pressure still persists, it can only be a few things, right?





But what's too high of pressure? Seems yours isn't all that high, but it changed/went up a bit hmmmm..........So, thinking that in some of these unresolved mystery cases that only marginal growth of barnacles/mouse poop/build up of lake matter down in and around the cylinder walls and flow gates can disrupt critical water flow patterns around those cylinders, so perhaps just one or two holes in particular is more susceptible then others due their position juxtaposed to water inflow and flow through patterns.

Can you isolate the heating to just one side of the engine? Just one hole? Can you do some creative instrumentation?.........A type K thermocouple alum taped strategically to each spark plug body in-turn and take 6 test runs, record/note the temp data........Isolate a higher heat to perhaps just one cylinder, go from there.

Inspect(re)/de-scale the outer cylinder wall/s, check cylinder H2O flow through gated areas in and around suspect hole, check its leak-down, check its fuel input path, reed valve okay, etc, etc

>>>>> Added $.02 <<<<<<<